Why would the Board of Alderman take up legislation that would turn off the HEPA filters in bars and restaurants across St. Louis just as swine flu pandemic threatens. The CDC says HEPA filters strip viruses from indoor air:
“Does a HEPA filter remove smallpox virus? Can a makeshift isolation room be created by bringing a portable HEPA filter into a regular private room?
Yes, HEPA filters do remove smallpox virus. HEPA filters are 99.97% efficient at removing particles that are greater than or equal to 0.3 microns in size, but their use will not create an airborne infection isolation room, (the precautions recommended for smallpox patients). The HEPA filter will not change the pressure relationship to the corridor unless the portable filter is set up as a negative pressure device. Self-closing doors will help to maintain the conditions and windows should be closed and sealed. If the HEPA filter is being used only to purify the room air, its effectiveness will vary depending on the size of the room and output of the device. A portable HEPA filter that produces 8 or more air changes per hour results in a 90% reduction of particles in 17 minutes in a room with the doors and windows closed. However, to be consistent with current guidelines for airborne infection isolation rooms, the goal should be 12 or more air changes per hour which would produce a 90% reduction in particles in 11 minutes.”
http://www.bt.cdc.gov/agent/smallpox/faq/patient_infection_control_issues.asp
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