To: Jim Willie CB who wrote (6009 ) 10/18/2001 1:41:40 PM From: Win Smith Read Replies (1) | Respond to Garwin talks about filters and such in nybooks.com :The first and most practical defense against biological warfare attack is to maintain "positive" pressure of filtered air within buildings. It takes a very small capital expenditure and a very small expenditure in power to provide a positive pressure so that normal winds will not infiltrate a building, and the anthrax spores or other microbes will be kept out. To do this the air intake to a normal building—whether an office building, an apartment building, or a private house—should be provided with a small blower that delivers air through a High Efficiency Particulate Airfilter (HEPA) at a rate that exceeds the leakage of air in or out of the building. Such "makeup" air will then produce excess pressure in the building so that air flows out through any cracks or apertures, blocking any inflow of unfiltered air. If no form of air intake exists, a window or a portion of a window can be removed to make one. It is interesting to note that any normal building, no matter how tightly closed, will have the same exposure to a biological warfare agent as it would if the windows were wide open—it takes longer for the agent to enter, but it stays there a much longer time. Positive-pressure filtered air largely eliminates this problem. nytimes.com There was ample evidence of that today, the most unsettling day this taut city has seen since Sept. 11. Whoever has made a target of newsrooms and Capitol Hill offices with letters containing white powder or other contaminants has succeeded in sowing confusion and anxiety, verging on terror, among the chattering classes of Washington — the people who set the capital's tone.
