Smokers -- or at least their tobacco smoke -- will have to stay away from nonsmokers under the latest version of ASHRAE's indoor ventilation standard.

The changes were announced in the 2007 edition of the society's Standard 62, “Ventilation for Acceptable Indoor Air Quality.”

“Standard 62.1 has served the building industry and the public as the most prominent standard on ventilation for indoor air quality,” said Dennis Stanke, chairman of the American Society of Heating, Refrigerating and Air-Conditioning Engineers committee that drafted the rules. “Changes in the 2007 standard build on the improvements published in the 2004 version, providing additional guidance for designers of building ventilation systems.”

For the first time, the society is requiring the full separation and independent ventilation of smoking areas. Earlier versions of the standard only set minimum ventilation rates for such locations. However, in recent years ASHRAE has moved away from trying to determine "acceptable" ventilation rates to clear secondhand smoke.

The scientific and medical communities have long held that ambient smoke from burning cigars, cigarettes and pipes is a human carcinogen and no level of it is completely safe, regardless of how many times smoke-filled air is cleaned or exchanged. ASHRAE released a position document in 2005 that reached a similar conclusion, and then-U.S. Surgeon General Richard Carmona issued an updated report on secondhand smoke in 2006 that including ASHRAE's research in its findings.

Both the society and surgeon general say smoke-free buildings are the best way to protect the public's health.

The report fueled the already-accelerating trend toward smokeless public places. Eighteen states have passed laws ban smoking in almost all public places, including bars and restaurants. Most of the bans have been enacted in the last five years, including four so far this year.

ASHRAE said its revisions will ensure that where smoking is permitted, nonsmokers will not involuntarily be exposed.

The society's standards are voluntary, but are often adopted by cities and states into building codes, so any changes could affect future construction or extensive renovations to existing structures.

More information on the revised rules is