Creating a Comfort Zone

There's something in the air -- the faint and persistent buzz of hazard. Some people are plainly scared. They've been told so often "it's not if but when" that images of terrorist attack pass through their minds every day. Some people seem untouched. They face the periodic and inscrutable announcements of threat with a mix of fatalism and defiance. But nobody doubts that they're living in a changed world.

After all, the unimaginable has already happened. The attacks of Sept. 11, 2001, were so unlikely and -- let's face it -- so successful that large-scale death from terrorism on American soil is no longer just a theoretical possibility.

So what does one do with that feeling and that fact?

It's a good question. And a really hard one to answer.

What follows in these pages is our attempt to help you come up with a reasonable and livable stance against the threat of terrorism. We're most definitely not providing answers, let alone The Answer. But we're offering some building materials that may be useful in constructing the very personal edifice that is peace of mind.

What we're offering is information: facts about the kind of threats the government says may be out there; the damage each can wreak; relevant policies and guidelines; and the myriad things people can do, buy, learn or talk about, should they choose to plan for a terrorist event.

What we can't tell you is how likely an attack is, not to mention when, where and what kind might occur, and how many people could be killed, injured or inconvenienced. Don't expect anyone else to tell you, either. It's a lot easier to detonate a truck bomb than to aerosolize a virus, but no expert can confidently focus on the former and forget about the latter. The full range of threats are described in a chart on page 29.

The Department of Homeland Security's five-step, color-coded index of terrorism threat is a way to telegraph federal agencies, state governments and other large entities how aggressively they should pursue the labor-intensive efforts required for hypervigilance. Changes in the index don't mean much, in practical terms, to individual citizens. Nevertheless, people are seeking a way to gauge -- and address -- the threat to themselves and their families.

A good place to start is online, at three Web sites run by the federal government, which usefully lay out options without giving orders. They are www.ready.gov (run by the Department of Homeland Security); www.fema.gov (by the Federal Emergency Management Agency); and www.cdc.gov (by the Centers for Disease Control and Prevention). The information they provide can also be obtained by mail and, in some cases, by phone. There are dozens and dozens of other sites -- government, academic, commercial, ideological -- providing advice about how to prepare for terrorist events.

Much of it falls into a category of what might be called "informed common sense."

For example, walls and roofs are pretty good barriers against mists, dusts and most forms of radiation. Filters that don't keep out things smaller than 10 microns aren't likely to be extremely useful against biological aerosols (like the one used in the Capitol Hill anthrax attacks) with particles of 1.5 to 3 microns. Wind dilutes as well as spreads airborne contaminants, so the heavier the breeze, the more quickly an area becomes safe to move around in.

Basic provisioning of the home is a similarly sensible issue, despite the lampooning it's gotten recently. Who can argue with a couple of days of food and water, a radio with spare batteries, and good maps in all the cars? These are measures that people living on hurricane-prone coasts have taken for granted for years.

While the government has advocated taking certain protective measures, many people have thought about things and chosen to do nothing. The probability that a person will be harmed or killed by a terrorist event is extremely low, by any credible estimation. This is true even for people living in and around Washington, a plausible high-priority target for terrorists.

What's the risk of some unlikely non-terrorist events? The Harvard Center for Risk Analysis (www.hcra.harvard.edu) has calculated some. The chance of dying in a motor-vehicle accident is 1 in 6,745; in a fire, 1 in 82,977; on a bicycle, 1 in 376,165; by a lightning strike, 1 in 4,468,159. Death by terrorism is less likely than any of these.

The risk of dying in a terrorist attack depends mostly on proximity -- how close a person is to the hazard in question, be it a bomb, a gas cloud or a powder-filled envelope. And being close is largely a matter of luck. It's hard to think of a way to reduce your chances of being in the wrong place at the wrong time without retreating from normal life altogether.

The record of terrorism suggests that -- except in cases where an attack is mounted in a confined space such as a bus -- fatally bad luck is relatively uncommon. In the World Trade Center attacks, 2,801 people were killed but about 15,000 people escaped the buildings. That's out of about 368,000 people who were working in Lower Manhattan at the time. Five people died in the anthrax attacks in the fall of 2001. Nobody knows how many people were exposed to the bacteria, but it was at least hundreds. When cultists released sarin nerve agent on three Tokyo subway lines in 1995 -- trains ridden by hundreds of thousands of passengers -- 5,500 riders received medical treatment. Twelve died.

The long-term effects on survivors also may not be as dire as many assume. The Japanese and American governments have been tracking the health of 86,572 people who received significant radiation exposure from the Hiroshima and Nagasaki atomic-bomb blasts. From 1950 through 1990, there were approximately 420 excess cancer deaths in this group attributable to radiation exposure. That's about 7 percent of all cancer deaths experienced by the exposed survivors.

Of course, planning for terrorism can become a disabling obsession. It's worth noting that many people with full-blown anxiety disorders believe that the more horrible an event is, the more likely it is to happen. They also believe that thinking about a feared event will somehow reduce its chances of happening. Neither belief is true.

One last thing bears keeping in mind. There are limits to "expertise" on the subject of how to avoid unseen and unpredictable health hazards. American history is instructive.

Between 1870 and 1920, the new science of bacteriology transformed the understanding of infectious disease. Scientists embraced the idea that many diseases are caused by distinct, transmissable microorganisms. This rapidly led physicians and public officials to offer advice to American citizens on how to avoid bacterial depredation in the home. They instructed housewives to scrub floors with hot water and lye, dust furniture, regularly wash curtains and walls, boil clothes and bed linen -- all in an effort to rid living spaces of microbe-laden dusts.

The problem was the new insight was only half-right. While there is a connection between hygiene and disease -- and changes in domestic practices undoubtedly prevented some infections -- scientists now know that dust and "contaminated" furnishings play almost no role in disease transmission. The backbreaking labor of a generation of women, many living in dwellings that didn't even have running water, was mostly a waste of time.

Insights into preparedness are emerging in our time. They, too, reflect much that is true about the world. But the usefulness of the information available in the marketplace or on the Internet -- even from reputable sources -- is unproved. The best advice may turn out to be lifesaving, but it may also turn out to induce needless effort, anguish and guilt.

In the end, it may be that the most obvious benefit of having a personal disaster plan is that it helps us push aside the nerve-racking subject of terrorism and get on with our lives and work. That's not a bad reason to have one.

No One Is Sure Where Terrorists Will Strike

First, some calculations, courtesy of Risk Management Solutions, a consulting firm that advises insurance companies on catastrophic risks:

The current terrorism risk in the United States is 0.5 events per year, or one event per 24 months.

If there is an attack, there's roughly a 50 percent chance that terrorists will employ conventional explosives. Intentional plane crashes, incendiary events and destruction of chemical depots, nuclear power plants or other industrial sites are less likely.

Least likely is the chance that the next attack will feature chemical, biological, radiological or nuclear weapons -- CBRN, in the trade. That is less than 10 percent.

Washington and New York City are at the top of the list of targets and in a category by themselves, RMS experts believe. A competing firm includes San Francisco in the first tier along with those two cities, but RMS sticks with Washington and New York alone.

Now, what can one say about these predictions?

Unquestionably, they are the product of laborious research, higher-order mathematics and hard-to-get expert opinion. But only time will tell whether they're right.

It's very difficult to say much about events that are exceedingly rare or, like many terrorist attack scenarios, haven't occurred even once. That's why almost every statement about terrorism and preparedness is swaddled in caveats.

Take a "dirty bomb," which does its damage by spreading radioactive dust. An explosion five blocks away is dangerous, but what about one five miles away?

"That's likely to be far enough away to avoid risk, but no one can make a categorical statement that it is far enough away to avoid risk," says Jonathan Links, a professor of environmental health sciences at Johns Hopkins University who is Baltimore's consultant on radiological terrorism.

A similar observation -- with details and distances changed -- holds for just about every other hazard.

Besides the federal government, the insurance industry is the one sector of American life that can't get around attempting rational estimates of terrorism risk. It must, in order to offer -- and price -- terrorism insurance. Insurance companies' exposure is enormous; the payouts from the Sept. 11, 2001, attacks are expected to be $40.2 billion.

Three companies in the United States are engaged in modeling terrorism catastrophes. All have extensive experience in quantifying and predicting natural hazard risks. They are RMS, of Newark, Calif.; EQECAT, of Oakland, Calif., and Applied Insurance Research, of Boston.

These companies list more than 240,000 potential targets in the United States and model attacks on a relatively small percentage of them. The damage estimates and attack probabilities they come up with are generally secret, although a few facts trickle out. For example, California's share of the total national risk of an attack is 8.5 percent, according to an EQECAT estimate done for the Workers' Compensation Insurance Rating Bureau of California. (None of the companies was willing to say what Washington's share is.)

However, there seems to be a consensus that the likeliest targets are government offices; "trophy buildings" such as skyscrapers; hazardous industrial sites, and transportation facilities such as bridges and tunnels. They provide the possibility of a high-profile attack causing enormous life and property loss, which appear to be terrorist goals.

It logically follows that people living outside urban centers are at a lower risk of attack. That conclusion doesn't conflict with the very real possibility that terrorists may choose to strike at something like a Midwest state fair simply to be counterintuitive. Such a possibility, however, barely raises the low risk of Midwesterners compared to East Coast city dwellers, because there are many, many central U.S. targets with the same likelihood of being chosen, experts believe.

Gary Hart, the former senator and presidential candidate who is sounding a clarion call for greater terrorism preparedness, personally thinks such an attack is next.

"My belief is that it will involve multiple targets in the inland United States, and will probably involve biological agents," he said last week.

His source of information?

"Intuition," he said. "It is calculated by trying to get inside the mind of the terrorist."

Sheltering in Place: When Home Is the Safest Place to Be

Q When might you most likely want to shelter in place?

A When 24 inches of snow falls in your neighborhood, making roads perilous and the fireplace inviting. And that is the best reason to lay in a three-day cache of food, water and medicine.

But those supplies -- in addition to a flashlight, a portable radio and extra batteries -- would also be useful in the event of the terrorist attack that federal authorities keep telling us to prepare for.

What is the difference between "sheltering in place" and a "safe room"?

Sheltering in place means bringing people and pets indoors, closing doors and windows and turning off the heating, cooling and ventilating systems. This offers protection from outside contaminants, says John H. Sorensen, an emergency preparedness expert at the Oak Ridge National Laboratory.

A safe room -- which Sorensen calls "expedient protection" -- ideally is a windowless space in the center of the home that provides "an extra barrier between a room you tape and seal and the rest of the house," he says. "It is only a short-term thing, one to two hours [other experts say five hours if each person has 10 square feet of floor space]. And you need to get out and ventilate that room after whatever you are protecting yourself from has passed."

Safe rooms work best with prior warning, such as an alarm or news flash about a chemical spill. Terrorists would likely strike without warning, he says.

What kind of attacks would require staying put?

Chemical, biological and radiological.

How might a chemical attack occur?

Through sabotage of an industrial facility or the release of chemicals transported by train or tanker truck, says Amy E. Smithson, a chemical and biological weapons expert at the Henry L. Stimson Center.

People nearest an incident may recognize an attack right away if they "smell something funny or see birds drop out of the sky," says Smithson. They should shut all windows and doors, turn off all ventilation systems and try to seal the house. (Remember that pre-cut plastic sheeting -- the thicker, the better -- and duct tape.)

If they believe they have been exposed to chemicals, they should strip, making sure to cut open such garments as T-shirts and dresses with scissors rather than pull them over the head.

Contaminated clothes should be stored in a plastic bag. Exposed individuals should wash themselves thoroughly from head to toe with soap and warm water, and remain inside until told by authorities the threat has dispersed, Smithson says.

What about bioterrorism?

That scenario could entail an aerosol release at a crowded event or at a transit point like an airport or Metro station, or through a ventilation system, says Smithson. In most circumstances, people wouldn't know they are inhaling these microscopic pathogens; hospitals would begin noting large numbers of people falling ill.

By the time the disease is identified, the pathogen would already have done its damage. But some diseases are so contagious, says Smithson, that "you may need to hunker down and stay away from other people" for two weeks or longer.

The smallpox incubation period, for example, is up to 17 days, and the disease itself can last up to a month. Pneumonic plague incubates for two or three days and lasts another one to six. This requires a far larger supply of food, water and medicine to avoid leaving home.

What about radiation exposure from a nuclear device?

While government officials do worry about a "Hiroshima-type" nuclear assault, an easier and likelier terrorist weapon is a "dirty bomb," says Jon Wolfsthal, a proliferation expert at the Carnegie Endowment for International Peace. Such a bomb combines standard explosives with such radiological substances as cobalt-60, strontium-90 or radioactive iodine, all used for industrial and medical purposes.

The worst injuries may be caused by the explosion and flying debris, but the radiation "can be really bad and you can get very high doses even after just a few minutes of exposure," Wolfsthal says.

"The rule of thumb is if you can hear the blast, you're probably too close and you want to leave the area quickly. If it's 10 blocks away and you are not sure, the best thing you can do is stay put. We are not talking about microscopic atoms or viruses, but dust particles and droplets."

If you choose to stay in place, shut the windows, turn off the ventilation system, remove all clothing and shower vigorously. Seek shelter in an interior, windowless room or a basement and get information on wind direction from radio or television.

"Weather usually moves from west to east," Wolfsthal notes, so a person in Rockville who learns of an attack on Capitol Hill is upwind, and therefore all right.

"And I wouldn't drink tap water," he adds.

There are two nuclear power plants within 75 miles of Washington: Calvert Cliffs in Lusby, Md., and North Anna in Spotsylvania County, Va. What should you do if radioactive material is released?

A siren or alert system would sound and, if you live within 10 miles of either plant, you should turn on a TV or radio for instructions regarding shelter and/or evacuation, said Patricia Milligan, a physicist with the Nuclear Regulatory Commission.

Those close to either nuclear plant should also take potassium iodide to guard against the effect of released radioactive iodine. Maryland officials handed out 36,000 such pills last August to schools, businesses and residents around Calvert Cliffs.

If you live within 50 miles, the primary concern is eating locally produced food. After the Chernobyl nuclear plant blew up in 1986, many Ukrainians were exposed to radioactive fallout through milk -- grass irradiated by the plant explosion was eaten by cows. So the protective action would be confiscating potentially contaminated food, and livestock would be fed stored grain.

Milligan considers it "highly unlikely" that people in the Washington area would suffer adverse health effects: "The hazards to public safety would be minimal."

What if you have pets?

Bring them inside if you shelter in place. Take them with you if you evacuate, she says. But only service animals, such as guide dogs, may be allowed in public shelters.

Staying Informed and Staying in Touch

"This is a test of the Emergency Alert System. . . . This is only a test."

Those familiar words, which have sporadically interrupted radio and television broadcasts for years, offer assurance that officials can deliver timely warnings in the event of an emergency.

But that's just a beginning.

Exactly how the government will communicate with residents and how residents will communicate with one another in an emergency has -- since Sept. 11, 2001 -- emerged as one of the primary challenges facing emergency planners.

Staying informed, particularly if there is an attack or other event at an unusual hour, could pose a major difficulty. Any such problems would be exacerbated under extreme conditions, such as a power outage, or when the communications network was overloaded.

The Emergency Alert System should work fine for anyone within range of a television or radio, and broadcast news outlets probably would provide blanket coverage of any dangerous situation. Police bullhorns and sirens also could be used to alert residents.

In addition, authorities make the following points:

o To make sure emergency broadcasts of official information are available when electricity isn't, it is important to have a battery-operated AM/FM radio.

"Information is power, and in an emergency, people without information feel powerless," said Merni Fitzgerald, public information officer for Fairfax County.

o A weather alert radio costs as little as $20 and can get warnings of threats other than weather emergencies.

Weather radios can remain on standby until a warning is issued from a nearby National Weather Service office. Some local jurisdictions say their emergency alerts will be made available that way. More expensive radio models can filter out messages not intended for your immediate area. For more information, visit the Web site at www.nws.noaa.gov/nwr.

"We've been getting a lot of inquiries about [radios] since Sept. 11," said Chris Alex, a meteorologist with the Weather Service branch that disseminates hazard warnings. "When these really shine is when you're asleep or other times when broadcast information is not readily accessible."

o Some counties and cities in the region have or are acquiring emergency notification systems that anyone can sign up for. In an emergency, the systems would send warnings to a device of your choosing, for example, a text-messaging mobile phone, a pager or an e-mail account.

Hundreds of Fairfax City residents have signed up to receive such messages, and Arlington County expects to have its system in place this spring. Fairfax and Montgomery counties are considering similar efforts.

"We have found it very helpful, particularly during the recent snowstorms," said Chris Fow, community relations specialist for Fairfax City. Family members and friends should plan how they will stay in touch during an emergency, authorities said.

As area residents may recall, cell phones, a common means of making emergency calls on most days, could not get through during the chaos of Sept. 11, 2001. The problem was essentially one of call volume: Wireless traffic in New York City was 1,400 percent higher than normal peak levels, and Washington's cell traffic was 400 percent higher, according to Travis Larson, a spokesman for the Cellular Telecommunications & Internet Association, a trade group.

"No public network -- the highways, the Internet, whatever -- is designed to handle everyone using it at the same time," Larson said.

But even if you can't get a voice call through, your cell phone may still communicate for you. Most new ones have text-messaging capability, a feature that worked well on Sept. 11 because text messages require less capacity and get through more easily.

"Voice and text messages take different paths through the network," said Jim Dailey, senior adviser on homeland security for the Federal Communications Commission. "The text message is a very fast data transmission."

For similar reasons, wireless e-mail gizmos may work when wireless voice calls can't get through. Because wireless e-mail worked on Sept. 11 when voice calls didn't, BlackBerry e-mail devices have been handed out to members of the House of Representatives. There are several models, starting around $400, and customers have to purchase a wireless service plan.

Authorities generally recommend having several means of communicating -- including e-mail, other Internet services, pagers and two-way radios -- because it is difficult to predict the effect of a disaster.

On the low-tech end, they suggest setting up a phone contact outside the region because often when local phone lines are jammed, long-distance lines are not.

"The public needs to make sure that they have redundant means of communication," said Dave Robertson, interim executive director of the Metropolitan Washington Council of Governments. "If one thing doesn't work, something else will."

Considering a Gas Mask? Be Sure It's a Good Fit

I am living proof that gas masks work. I strapped one on recently in the third-floor conference room of Geomet, a Germantown-based "health and personal safety" company. And then I chopped up a raw onion with a paring knife.

In the face of the bulb's chemical onslaught, I didn't shed a single tear. Nor did I detect a whiff of the onion's distinctive tang. If terrorists attack with diced onions, a gas mask will protect you.

Of course, VO -- Vidalia onion -- isn't what people are worried about these days. VX is. And GB, HD and other frightening combinations of the alphabet. Because of that fear, some consumers are curious about gas masks, or what are more broadly known as respirators.

The federal government does not endorse the idea of civilians donning gas masks. The answer to the very first question on the www.ready.gov Web site's FAQ section states: "The use of gas masks and hoods by the public during a chemical threat is not recommended due to legitimate safety concerns."

Those safety concerns are not trivial. Use a gas mask incorrectly and you can be killed by your own fumblings long before al Qaeda has a chance to get you.

This is not to say that the Department of Homeland Security is totally anti-mask. The Web site does mention that "filter masks" can help keep out germs from a biological attack or debris from an explosion, and it says that "something over your nose and mouth in an emergency is better than nothing."

The Filter Mask

That "something" starts with cheap, disposable filter masks found at hardware and paint supply stores. These respirators are rated by the size of particle they protect against and the durability of the filter material. A mask rated 95 means it will stop 95 percent of particles that are 0.3 microns in diameter or larger. The other particle size ratings are 99 (filters out 99 percent of the 0.3-micron particles) and 100 (filters out 99.97 percent, an efficiency comparable to a HEPA filter).

The most common mask is an N95. The N means that the material it is made of is not oil-resistant. A P rating means it is oilproof; an R rating means it is oilproof but can be used a maximum of eight hours.

The anthrax spores in the letter mailed to then-Senate Majority Leader Thomas A. Daschle (D-S.D.) were 1.5 to 3 microns in diameter, so an N95 can safeguard against the disease. (Smallpox, on the other hand, is smaller than 0.3 microns.) In his book "When Every Moment Counts," Senate Majority Leader Bill Frist (R-Tenn.) recommends that N95 masks be included in every disaster supply kit. They start at about $1.

If you decide to get an N95 mask, be sure it has a moldable metal noseband and crimp it when you use the mask. It will help create a better seal.

Some masks have plastic valves to release your expelled breath so the respirator doesn't get too hot and your glasses don't fog.

Some N95 masks are called "harmful dust respirators." Stay away from what are called "comfort" respirators, masks designed to wear while you're raking leaves or sweeping the floor. (A crude rule of thumb: A mask that is held on by a single elastic strap is less likely to be an N95 than one that has two straps.)

And if you're stuck without a mask, you can follow the advice on Ready.gov and breathe through fabric, such as a folded-up cotton T-shirt or diaper.

Half Masks

Next up in price are what are known as elastomeric respirators. These are typically half masks that cover the nose and mouth and can be fitted with different filters. A P100 or HEPA filter strains out particles, including the sort of radiological particles scattered by a "dirty" bomb. Various types of charcoal filters can neutralize small amounts of certain industrial chemicals, such as ammonia and pesticides.

Prices start at about $10. They won't stop the nastier nerve gases, but if you're several miles from an overturned chlorine tanker and a cloud is coming your way, they do afford some protection. Since the mask doesn't cover the eyes or rest of the skin, you can still get a dose of chemicals that way, but they do protect the lungs, the primary route of attack with gas.

Manufacturers of N95 masks and half masks are quick to point out that their products were not designed with chemical, biological or radiological attacks in mind.

Masks, Escape Hoods

Most gas-mask manufacturers and retailers agree with Homeland Security Secretary Tom Ridge that gas masks don't belong in the hands of the public. Experts say they are too difficult for civilians to fit and use properly. Most can't be worn with glasses or by men with beards.

The alternative is the escape hood -- basically a plastic bag with a rubber neck dam and a particle/chemical filter. Unlike a gas mask, which requires that straps be carefully adjusted so there's a leakproof seal between face and mask, an escape hood pretty much seals automatically around the user's neck after it's pulled on.

ILC Dover, the company that makes spacesuits for NASA, has introduced a civilian escape hood. Called the SCape, it's packed in a container about as long and a little wider than a box of tissues. It costs $199.

The SCape is what's called a "positive pressure" unit. A tiny motor is activated when the hood is pulled from its box. The motor sucks air through a set of filters and into the hood.

Other civilian models include the Gas Mask Hood by Mine Safety Appliances, one of the leading respirator manufacturers, and Survivair's Quick2000, the type purchased for federal workers on Capitol Hill. They're each about $180. Both of these hoods require wearers to draw in the air themselves through the filter -- fine for normal people but a potential hardship for those with respiratory problems.

Hoods can be used only once.

These devices join products that have been marketed to frequent travelers in recent years: smoke hoods. Smoke hoods are specifically designed to protect against deadly carbon monoxide during a fire. They don't protect against nerve gas.

No mask or hood lasts forever. Its filter will eventually get clogged.

Children

Respirator companies don't make products in sizes that will fit children. You may be able to find N95 respirators sized for smaller adults. The challenge will be fitting it to a child's face to keep out contaminated air.

Some escape-hood manufacturers make products just for children. ILC Dover says its Baby SCape hood fits children ages 3 and younger. Safer America, a New York store, sells several hoods and suits for children, toddlers and babies, at $295 to $500.

With their smaller lungs, children may have trouble pulling air in through a filter. Most children's hoods or masks are supplied air, meaning a motor blows air into the unit.

ILC Dover also makes a clear plastic, air-filtering container into which owners can insert a dog or cat in a kennel. The Pet Shield is $350 for animals up to 50 pounds, $450 for those 50 to 100 pounds.

Where to get them: Geomet Technologies Inc. distributes a wide range of gas masks and escape hoods: www.geomet.com or 301-428-9898. Safer America is at www.saferamerica.com or 877-774-4055. MSA sells its Gas Mask Hood through amazon.com; information is at www.msasafetyworks.com, or call 888-672-4692. ILC Dover sells through its Web site: www.ilcdover.com, or call 800-631-9567. The Quick2000 is available through Survivair: www.survivair.com, or call 888-274-8535.

How a Masks Works

All respirators stop working eventually, though in the case of half-masks and military-style gas masks, filter canisters can be replaced. To understand why, it's useful to know how respirators work in the first place:

An N95, P100 or HEPA filter acts like the colander you dump boiled pasta into: It simply allows small things through while stopping big things. Those big things include dangerous spores and debris. The small things are molecules of air.

Activated charcoal, the magic ingredient in masks that neutralize nerve gas and harmful chemicals, works in a different way. Imagine a river that widens into a huge lake before narrowing and continuing its flow. The lake is speckled with millions of tiny inlets. That's a piece of activated charcoal. Now imagine millions of speedboats racing down the river. The boats are the molecules of a dangerous chemical. Instead of continuing its journey to the sea, each speedboat docks in a different inlet as it enters the lake.

As long as there are more inlets than boats -- or more pores in the charcoal than chemical molecules -- the wearer is safe.

But no filter lasts forever. A particulate filter will eventually become so clogged with particles that oxygen won't penetrate it. Bad news for the wearer. And an activated charcoal mask will eventually lose its chemical-cleansing abilities, allowing untreated air to enter. Bad news for the wearer if that air contains something dangerous.

A hood or mask could stop working in less than 20 minutes, depending on how contaminated the air was. The batteries in powered-air units typically conk out after about four hours, though the filter may have been overrun long before then.

Air Filters: Working All the Time

Plastic sheeting and duct tape have gotten all the headlines (and many of the punch lines) in the terrorism-preparation discussion, but some experts think there are ways to make your home safer that need not involve sealing off a single window with either product.

Instead, the U.S. Department of Homeland Security's Ready.gov Web site suggests buying a portable air purifier -- typically an under-$200 purchase.

While such devices are generally used by people with asthma or allergies to catch dust or cat dander, they might also help clear the air of harmful agents.

Richard L. Garwin, a senior fellow for science and technology at the Council on Foreign Relations, calculates that a typical room air cleaner could reduce the number of microbes in the air by 83 percent. Plastic sheeting over air vents could provide further protection in the event of an attack.

Proponents of portable air filters point out that these appliances are typically left on at all times. Gas masks or escape hoods, on the other hand, are the kind of things people only use after hearing that harmful agents could be in the air -- in other words, after they may have already been exposed.

"Generally speaking, filtration is a very effective means of protecting against chemical and biological threats," said Michael C. Janus, the head of building protection at Battelle Memorial Institute, a research and development firm that has overseen the installation of air-protection safeguards for such Washington clients as the Department of Defense, the Department of Justice and the Federal Emergency Management Agency.

Janus said that the consumer-grade, portable air filters people can buy at stores such as Home Depot would provide a "moderate level" of protection in the event of an attack.

"It's all dependent on the threat," he said. "If it happens in the middle of Washington, DC, and you live in Northern Virginia or Montgomery County, that moderate level is more than appropriate . . . if your house doesn't sit next to the White House, that's probably an appropriate level."

Established air-cleaner manufacturers, however, can be reluctant to push bioterrorism defense as a new selling point for their products.

"Our stance is that you're more likely to die from the pollution you breathe every day than from a terrorist attack," said Frank Hammas, president of the North American subsidiary of IQAir Inc., a Swiss company with an offshoot in Santa Fe Springs, Calif.

Following the anthrax scare in 2001, IQAir got calls from so many concerned customers and dealers that it released a statement pointing out that its systems "have not been designed for, nor are there any claims made as to their effectiveness as a civil biodefense measure."

"I don't know, and I don't think there exist, studies that show us how effective these filters would be at removing biologic agents," said Angelo Acquista, medical director of the New York City Office of Emergency Management and author of "The Survival Guide: What to Do in a Biological, Chemical or Nuclear Emergency," published this month by Random House.

Herbert Lin, a senior scientist at the National Research Council, keeps a portable air filter in his office, but that's because of dust and pollen allergies, not because he thinks it would be effective against a bioterrorist attack.

At home, he has something even more effective at clearing the air: a "positive pressure" HEPA (High Efficiency Particulate Air) filter, which cost more than $4,000 to install on his home heating system as part of a larger home upgrade. HEPA filters are built to a standard set by the U.S. government to protect the air nuclear scientists breathe on the job. Where portable air filters only clean air that's already in the room, "positive pressure" systems are devised so that filtered air comes into an environment at a rate faster than outside air can enter through cracks or imperfections in the walls.

"It's easier for me to breathe now and it happens to have the side benefit of protecting against most biological warfare agents," said Lin. But he emphasizes that he got the system because of his allergies, not because of fears about bioterrorism. "Unless you're really, really paranoid, it's not worth it to do this just for the anthrax part, it just isn't," he said. "That would be stupid."

While Lin's system required a professional installation, new air filtering companies such as American Safe Room Inc. advertise systems that can be installed on the fly.

American Safe Room, based in Oregon and founded after the terrorist attacks of Sept. 11, 2001, sells two such models of positive pressure air filters, priced at $1,270 and $1,746. While portable air filters require an electric current, American Safe Room's products can operate off a car battery for up to 18 hours, and for longer when powered by a hand crank. Company founder Len Henrikson said the firm sells five or six units in a typical week. But it saw demand surge to a few dozen orders a day the last time the Department of Homeland Security raised the terror alert level.

"We were scrambling," said Henrikson. "Whatever they say on the news, people react to that."

Henrikson said he made a decision early on not to raise his prices if an actual terrorist attack sends orders for his product through the roof. "We like making money and making sales, but it doesn't come to that," he said.

Detection Devices May Offer an Early Read on the Danger

Although current technology can identify radiation and many biological and chemical warfare agents, detection equipment tends to be reactive -- engaged after an attack. Its most practical value is to provide critical information to first responders.

The exceptions are conventional-explosive and radiation detectors in use at airports, seaports and border checkpoints. Extremely sensitive truck-size "portal monitors" can catch even traces of radioactive materials passing through.

And 7,000 of the 9,000 border, port and airport inspectors wear pager-size detectors on their belts, inconspicuously scanning travelers arriving in the United States for dirty-bomb-grade radiation, according to Dean Boyd, spokesman for the new Bureau of Customs and Border Protection.

Government sources often won't comment on detection deployments. But here's a rundown on some of the detectors in place in the Washington area, as well as personal detectors you can buy:

o The Washington Metropolitan Area Transit Authority began testing a chemical detection system in Metro stations in 1999. By year's end, 12 of 47 stations will have detectors able to detect blister agents and nerve agents, which include tabun and sarin. The system alerts Metro personnel to the station involved, the location in the station and what kind of chemical is present. Lt. Leslie Campbell, counterterrorism coordinator for Metro police, says the remote analysis cuts 40 minutes off the arrival time of first responders.

Also, Metro police carry pager-size detectors that vibrate or sound an alarm when sensing radiation, and two dozen officer-canine teams roam stations to detect explosives.

o The Department of Homeland Security is equipping the Environmental Protection Agency with air filters that within 24 hours of a biological attack can identify the pathogen, how much was dispersed and how many people may be affected, says Homeland spokesman Brian Roehrkasse. After the EPA -- which was already monitoring its air -- the filters will be installed in other, unspecified "urban centers."

o D.C. police won't comment on "anything related to security," but area fire departments are equipped with hazardous-materials detectors. District firehouses have radiation detectors, including recalibrated Cold War-era Geiger counters, and District hazmat units have more sophisticated radiation and chemical detectors.

Fairfax County's hazmat teams have hand-held radiation detectors and chemical detectors that can sense "all military and toxic industrial chemicals," says Daryl Louder, hazmat program manager. Radiation detectors are deployed at the county's four hazmat stations, and the county is testing a home pregnancy test-style detector that changes color when exposed to a biological agent.

Montgomery County, too, is using an array of portable detection equipment for sensing biochemical agents and radiation.

Jim Schwartz, assistant chief of operations for the Arlington County Fire Department, says most of the metropolitan area counties have about "the same capabilities and are focused on the same risks and threat." In the past year or so, the counties have upgraded detection equipment and now monitor for radiation 24 hours a day.

o U.S. Park Police have put "air samplers" at undisclosed locations and have used radiological testers during some public events.

o The U.S. Postal Service is testing a system in Baltimore that senses anthrax and other biological agents. If effective, it eventually will be installed in all 282 mail-processing plants nationwide to protect postal workers as well as mail recipients.

As public concern has increased, so has the sale of retail detection devices for personal use. Many of them have been sold by survivalist companies and medical supply dealers for years. Some experts doubt that civilians need radiation or chemical detectors.

Further, they warn that civilians not experienced at reading radiation levels may panic if a highly sensitive and expensive meter signals a "false positive" alert when it is, in fact, registering only safe, low-level radiation which occurs naturally.

Here's a sampling of what is being marketed for personal security:

o VigiWATCH, a Swiss company that has made watches for more than a century and is known for its high-tech products, is selling a standard-size wristwatch for $1,100 that not only keeps time but also measures radioactivity reaching the wearer and cumulative doses.

o NukAlert, a $160 key-chain radiation detector, was put on the market last month by KI4U Inc., a licensed radiological laboratory in Gonzales, Tex.

The detector, which has a 10-year battery, "chirps" when it senses dangerous radiation; the more frequently it chirps, the higher the radiation levels. It was tested independently by an unaffiliated radiation lab to certify that it works. So far, 5,000 have been sold online, says KI4U President Shane Connor.

o USA GUARD, a Vermont company, sells an $80 pen-size radiation detector called "Pen Dosimeter" and a $350 MGP DMC 2000X pager-style radiation detector that are commonly used in hospitals and by the military. The company also makes an "M8" civilian version of military chemical-detector paper that changes color when it comes into contact with dangerous chemical agents. A book of 25 sheets sells for $10.

Connor warns that some personal detectors are too sensitive and can be set off by normal radiation levels. Better detectors are being developed.

Dwayne Lindner, who heads the biochem defense division at Sandia National Laboratories, which developed the system being used by Metro, says several national-security labs are developing a variety of "advanced detection systems."

One of Sandia's most promising systems, now in field trials, is a suitcase-size device called Microchemlab that is designed to detect a wide variety of threats, including chemical, biological and industrial (such as dioxins and sulfuric acid). Lindner expects it to be available in 2007.

Neighbors Uniting to Help Each Other

Last fall the Burleith Citizens Association sent out a questionnaire to all residents of the Northwest Washington neighborhood, asking some fundamental emergency-oriented questions: Who had training in first aid? Who might need transportation and who might be available to drive others? Who had pets left alone in the house during the daytime? Who had ham radios?

The response was abysmal.

Perhaps only those who have lived through a terrorist attack realize how useful some simple information can be. Take Diane Lapson, vice president of her Manhattan apartment building's tenant association. Her first instinct was to flee uptown when the World Trade Center towers collapsed in a roar just five blocks away. Pausing in the lobby, however, she saw the faces of frightened elderly tenants and was overcome by another, more powerful instinct -- to help. Along with a group of fellow residents, Lapson organized assistance for homebound tenants, coordinated an effort to get food and water to workers at Ground Zero, and even found volunteers to help a local druggist get prescribed medicines to those who desperately needed them.

"It was pretty amazing what was going on here," said Lapson.

"It made our community so unified and created bonds that will never be broken." It also changed forever her view of human nature. "It's a very deep spiritual experience when you discover that for many people compassion is a stronger human instinct than survival."

Although the actions Lapson and her fellow tenants took that fateful day and for many days after arose spontaneously, they were more effective because a community association already existed. "It helps to have people you know and trust in charge," Lapson said. "Fifty percent of the panic was gone because of that." Even so, they didn't have much basic information.

Organizing a community is one of the most fundamental steps in neighborhood preparedness. The Red Cross recommends a neighborhood meeting to discuss emergency plans, as well as establishing a Neighborhood Watch, to report on suspicious activity and obtaining a copy of "Terrorism: Preparing for the Unexpected," a brochure available from local Red Cross chapters.

As a terror threat grows, the Red Cross recommends a neighborhood meeting to identify neighbors who are elderly or have special needs, assist them in developing a personal disaster plan, and provide disaster supply kits to those who request them. In the event of a high or severe terrorist threat, preparations should be made to either evacuate neighbors in need or place then in appropriate home shelters.

From her perspective at the center of a disaster, Lapson has a few more suggestions. It is important, she said, for volunteers to have specific jobs in advance. A lot of confusion can be avoided that way. She cites a Johns Hopkins study that says 75 to 80 percent of people will want to help in the event of a disaster, and she suggests that doctors, nurses, and others with useful skills be identified in the community.

Lapson's tenant association has what she calls an "A list" of people with special needs. A printed sheet with emergency contact numbers and other vital information was slipped under each apartment door with the request that residents fill it out and return it to the association. "I don't think people are as neurotic about privacy as they once were," said Lapson, "especially when they saw firsthand how important this is."

That importance has not yet dawned on Burleith.

Nevertheless, community leaders continue to try to prepare their neighborhood. They've arranged with the Roam Secure Alert Network, a private security company, to receive alerts on their cell phones and pagers.

They're working closely with nearby Georgetown University, which is testing its newly installed sirens. Mayor Anthony A. Williams will be speaking to the community soon about emergency preparedness.

Lapson said the benefits of unifying a community go beyond emergency preparedness. Wonderful friendships have emerged in her own building. "We are living such closed lives here in the U.S.," she said. "No one knows their neighbors. . . . Even if disaster never strikes, people will at least know one another well enough to have a party once a year."

Building Managers Plan for the Worst

The 460 people who work in a 12-story office building on Vermont Avenue NW all carry a miniature flashlight on their key chains. If there is a power failure during an attack, they will find their way down stairwells coated with glow-in-the-dark paint.

If an evacuation is deemed necessary, building operators will scan a list of disabled employees to make sure they receive any assistance or special equipment they need to leave the building.

And in the first moments after an attack, people will rip open emergency kits stashed in first-floor fire-control rooms that go beyond the basics to include battery-operated televisions, bullhorns and crowbars.

These are just a few of the security upgrades that John Akridge Cos., the firm that manages the property, has made over the past few months to prepare for a terrorist attack.

Concerned property managers checked buildings for vulnerabilities after Sept. 11, 2001, but the growing likelihood of a war in Iraq and recent terror alerts have prompted many to take a second look. In the year and a half since those attacks, building managers have struggled to keep up with a growing list of chemical, biological and radiological threats that were once inconceivable.

"On my desk, I probably have four emergency preparedness manuals," said Kathy Barnes, head of property management for Akridge.

Workers in commercial or government office buildings or residents of high-rise apartment buildings who are concerned about the threat of terrorism may want to speak to their office administrators or property managers to find out if they are making similar changes. By becoming familiar with safety procedures in advance, tenants and residents may be better equipped to respond in an emergency.

For example, both Akridge and Kaempfer Co., another manager of local office buildings, have modified ventilation systems so they can be turned off at a moment's notice to minimize the intake of airborne biological or chemical weapons agents.

That capability may protect people within a building from exposure for at least several hours, if not more. However, that solution depends on building supervisors learning of an attack in time to shut down the system.

Because there may be no advance warning, several government agencies, including the National Institute for Occupational Safety and Health, suggest that building operators consider improving buildings' existing filtration systems to catch finer particles. Since those systems are always on, they can provide constant protection against an attack.

"Increasing filter efficiency is one of the few measures that can be implemented in advance" to mitigate the effects of a chemical or biological attack, according to a government report on building security. The full handbook is only 28 pages and is available online at www.cdc.gov/niosh/bldvent/2002-139.html.

In addition to ventilation and filtration systems, government advisory guides stress basic physical building security.

Since Sept.11, more offices and apartment buildings have required photo identification or installed electronic entry systems. But unless employees or residents are also trained to keep out strangers, their effectiveness can be compromised, said Wes Brown, who hunts for holes in building security for Barton Protective Services.

"Seventy or 80 percent of the security breaches we see are human failures," Brown said.

One of the most common ways people undermine multimillion-dollar security systems, he said, is by letting people without authorization follow them through doors or off elevators.

Kaempfer tried to prevent such breaches at its nine area office buildings during the recent Code Orange alert by requiring tenants to register visitors a day in advance and securing loading docks 24 hours a day.

Akridge is compelling all of its building-services workers, including cleaning and garbage-collection crews, to undergo basic security training, such as learning how to identify suspicious packages and respond to bomb threats. Building-maintenance jobs are frequently outsourced, and subcontracted workers can stretch a building's safety net because they are often not subject to the same background checks and training requirements as workers hired directly.

Some apartment buildings have already stopped letting delivery people take their goods straight to residents' doors. At the Lansburgh apartment building on Eighth Street NW, for instance, pizza never makes it past the front desk.

In Uncertain Times, a Prepared Traveler Is a Wise Traveler

You can't safeguard against the possibility of a disrupted trip, or being stranded abroad in the event of a terrorist attack. But there are precautions you can take to minimize potential problems. Here are answers to commonly asked questions:

Q Should I stay home, or should I vacation as planned?

A Because each person has a different comfort zone, no one can make this decision for you. While some get nervous at the thought of being away if there is a chance of terrorist attack, others stand ready to pounce on travel bargains that may erupt when airplanes and hotels go unfilled.

Staying informed and in touch is key. Government resources for travel warnings and advisories include the U.S. State Department (888-407-4747, www.travel.state.gov), the U.K. Foreign & Commonwealth Office (www.fco.gov.uk) and the Canada Department of Foreign Affairs (www.voyage.gc.ca/dest/index.asp). Commercial resources on the Web include World Travel Watch (www.travelerstales.com/wtw) and Air Security International (www.airsecurity.com).

Take a cell phone if traveling domestically. If traveling abroad, consider renting a cell phone (most U.S. wireless phones do not work outside the country); an international cell phone at WorldCell.com, for example, rents for $75 a week, plus call charges. In addition, get a Web-based e-mail account, such as those offered by Yahoo.com, so you can receive and send messages from Internet cafes.

In the immediate aftermath of Sept. 11, 2001, many U.S. travelers were stranded. Is this a possibility in the event of another attack? How can I avoid being stuck?

After Sept. 11, airports throughout the United States were shut down for several days. But this would not be an automatic consequence of another terrorist attack, especially one without air travel involvement.

The more practical concern is whether any of the major airlines in bankruptcy, or close to it, will suddenly stop flying in the event of war with Iraq. Analysts have been warning that war will result in a sharp hike in jet fuel prices, which, coupled with a sudden drop-off in passengers, could further weaken airlines such as United and US Airways, already in Chapter 11 bankruptcy proceedings, and American, which is threatening to declare bankruptcy. History proves the concern may be warranted -- passengers were caught short when Eastern Air Lines ceased operations just days after the Persian Gulf War erupted and when Midway Airlines stopped operating immediately after Sept. 11.

While it may make sense to book flights on healthier airlines, such as JetBlue, Southwest, Northwest and Continental, that's not always practical. And booking on a foreign carrier is not necessarily better; many also have fiscal problems and, when airports finally reopened after Sept. 11, only Canadian and U.S. carriers were initially allowed to land in the United States.

David Stempler, president of the Air Travelers Association, an activist group, said it is unlikely that United, US Airways or American will go out of business unless there is a prolonged ordeal. And even in a worst-case scenario, federal law requires that other carriers accept the tickets of a bankrupt airline on a space-available basis.

"Know before you go," Stempler said. He recommends that travelers familiarize themselves with alternative airport gateways and with other transportation options, such as trains and car rentals. He also suggested getting paper tickets when possible; they usually cost more, but are easier to transfer to another airline.

Picking up a free flight guide at the airport upon departure (or downloading the information from the Internet) can give you an advantage. For example, if Reagan National were closed down but BWI were still open, you could figure out what airlines go to BWI without standing in line.

I've paid for my upcoming vacation in advance. Is there any way of getting my money back without penalty if I change my mind and want to cancel?

In recent weeks, more airlines, cruise lines and tour operators have tried to reassure travelers by relaxing their cancellation penalties or offering their own optional insurance, allowing customers to cancel with fewer penalties.

US Airways, for example, announced its "peace of mind" flexible travel policy that will allow customers to make changes to previously booked tickets without incurring penalty fees if a Code Red alert is declared. Delta said it will suspend penalties on transatlantic flights booked March 5-31. Other companies that have instituted new cancellation or insurance policies include Virgin Atlantic, United, Continental, American, Crystal Cruises, Royal Caribbean, Radisson Seven Seas Cruises, Superclubs, Trafalgar Tours, Celebrity Cruises, Uniworld, Ritz Tours and Seabourn Cruise Line.

Most travel insurance policies will cover trip cancellation or interruption due to a terrorist incident in your destination city; some also will cover your departure city. Travelguard (www.travelguard.com), for example, offers a policy that provides coverage if the city you are scheduled to visit has been the site of a terrorist attack within 30 days of your visit. But war in Iraq would not qualify.

"Terrorism is actually included in nearly all travel insurance policies if the policy is purchased within seven to 14 days of the traveler's first trip payment," said Jim Grace, president of Insuremytrip.com, a clearinghouse for 11 travel insurance companies.

Read the cancellation policy fine print for your tour, cruise or flight and ask if penalties have been eased in light of the world situation. Before purchasing travel insurance, read the policy offered with your package, and compare it to a policy that you could purchase independently. For example, some policies with terrorist clauses cover 30 days after an attack, while others cover only seven.

If terrorist attack coverage costs a few dollars more, pay it.

From Israel, Lessons in Civil Defense

JERUSALEM -- Having already experienced an Iraqi missile attack during the 1991 Persian Gulf War, the Israeli government says it is now much better organized for civil defense than it was 12 years ago.

Officials say the goal is to provide the gear and the information necessary so Israeli citizens can be relatively certain of what to do and how to protect themselves in the event of an attack.

Fear and lack of preparation were major problems in Israel the last time the United States went to war with Iraq. Of the 74 Israelis who died in cases listed as attack-related, all but six died of heart problems blamed on war-related stress, according to the National Insurance Institute.

Israel revamped its entire civil defense system in the aftermath of the Gulf War, creating reinforced safe areas to provide protection against direct conventional attack as well as other types of threats. The new Home Front Command, a component of the Israeli Defense Forces (IDF), has extensive authority over almost all of Israel's civil, police and medical services in the event of national emergency.

"The Israeli public is one of the most highly protected populations," said Brig. Gen. Ruth Yaron, spokeswoman for the IDF.

Despite nationwide preparations and an early warning system, however, recent polling indicates Israelis are still skeptical about whether preparations are sufficient and adequate to offer real protection.

In the Gulf War, only two deaths were considered directly related to damage from Iraqi Scud missiles or shrapnel resulting from attempts to shoot them down with U.S. Patriot missiles. The National Insurance Institute said four people suffocated from improper use of gas masks.

Central to the Israeli civil defense plan is the idea that security is created by a progressive series of systems that alert the public, provide information and tools and create specific measures for safety under attack. The Home Front Command's doctrine of civil defense "can be thought of as concentric circles of increasing protection, with the individual citizen at their center," said Col. Gili Shenhar, special assistant to the Home Front commander.

The outer circles include an early warning system based on a national system of sirens and a link to all Israeli radio and television stations. The inner circles are based on "protected space" and "personal protection kits."

The concept of protected space involves a location that is easy to reach and capable of providing those who stay in it with protection against both conventional and nonconventional weapons for several hours. By law, every new apartment building, or addition to existing structures built since 1992, must be equipped with an "apartment protected space" or "floor protected space." These are built with extra-thick concrete walls and only one window and door, both of which must be resistant to explosions and gases.

Israelis who live in older buildings have been instructed to designate an inner room with one window as a protected space. When notified by the Home Front Command, they are to prepare the room by covering the door and window of the room with plastic sheeting and equip it with canned goods, battery-operated radios, extra batteries and heavy-duty tape. (The government has capped the cost of batteries to prevent price-gouging.) In addition, every household is instructed to have at least three gallons of bottled water per person, in case the nation's water supply becomes contaminated.

By law, all public areas, such as shopping malls, large office buildings, schools and community centers, must have adequate bomb shelters. Tel Aviv's Central Bus Station, in an area where many migrant workers live, would serve as a communal bomb shelter capable of housing hundreds of people.

All Israeli citizens, as well as tourists and foreign workers, are entitled to a free personal protection kit, which includes a gas mask and injectable atropine to combat the effects of nerve gas. Accompanying instructions are in Hebrew, Arabic, Russian and English. Translations into Amharic, Spanish and Braille are being prepared.

There are also special masks for infants and children, the elderly and individuals with respiratory difficulties. A tent-like device is available for disabled individuals unable or unwilling to wear a mask. People who use assisted breathing devices will be provided with a device to hook their gas mask filters to home and portable ventilators.

The government estimates that more than 90 percent of Israelis now have gas masks. Foreign tourists will receive gas masks at their hotels, and students will get them through their universities. Palestinians living in the parts of the territories under Israeli Civil Administration and Palestinians who hold Israeli identity cards also are entitled to free kits.

The Education Ministry, in coordination with the Home Front Command, has conducted emergency drills and trained children how to put on their masks. In most high schools, teams of students and teachers have been specially trained.

Israelis have been instructed not to open their protection kits before they are told to do so. During the Gulf War, several dozen people were injured when they accidentally injected themselves with atropine, a chemical antidote for nerve agents.

Soldiers and emergency personnel have already received smallpox vaccinations. The military is also prepared to distribute potassium iodide tablets, which can counteract effects of radiation exposure. The Health Ministry said it has prepared family drug kits, including antibiotics, but these have not been distributed.

In the event of a missile attack, sirens will sound throughout the country. Television and radio stations will broadcast a Hebrew code, Homat Barzel, or "Iron Wall." Israelis will be directed to turn off air conditioners and electric appliances, close water taps and gas canisters, move to their designated protected space and seal the opening.

Text-beepers have been distributed to the hearing-impaired so that they can receive all civil defense warnings. The IDF has set up a multilingual Web site concerning preparations, which registers about 4,000 hits a day, according to Shenhar of the Home Front Command. Volunteer hot lines are open on an increased schedule. The Israel Medical Association is running emergency hot lines for doctors and the public, providing information on availability of vital health services and updates on treatment of biological and chemical attacks.

Despite the preparations, there is still concern here about infrastructure and compliance with regulations. There has been criticism that schools do not have sufficient shelter for their students and that many security procedures in private homes remain substandard.

Furthermore, critics say that many existing shelters are not serviceable. In routine times, they are used as synagogues, clubhouses and storage spaces, and some are filled with equipment and furniture. Others are neglected and unsanitary. Municipal authorities are responsible for maintaining public shelters, but consumer groups report that they have not done so.

According to a recently published research study, only 14 percent of the population trusts the usefulness of gas masks and the concept of protected space. The Jerusalem Post has reported that an estimated 25 percent of Israelis with children intend to take their families to the countryside, away from urban centers. There are other estimates that 250,000 people may try to leave the country if it comes under attack. Officials say they cannot guarantee that Israeli commercial airports will be functioning.