Personal Planning
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 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.

-- Mike Musgrove
Washington Post Staff Writer