Specific Strategies to Reduce Smoke Exposure
The most common advisory issued
during a smoke episode is to stay indoors. The usefulness of this strategy
depends on how well the building limits smoke from coming in from outdoors and
on minimizing indoor pollution sources. Staying indoors may therefore provide
some protection, especially in a tightly closed, air-conditioned home in which
the air conditioner re-circulates indoor air. Generally, newer homes are
“tighter” and keep ambient air pollution out more effectively than older homes.
with the doors and windows closed can usually reduce exposure to ambient air
about a third or more. Homes with central air conditioning generally recirculate
indoor air, though some outdoor smoky air can still be drawn inside (e.g., when
people enter or exit). In homes without air conditioning, indoor concentrations
of fine particles can approach 70 to 100 percent of the outdoor levels. In very
leaky homes and buildings, outdoor particles can easily infiltrate indoors, so
guidance to stay inside may offer little protection. In
any home, if doors and windows are left open, particle levels indoors and
outdoors will be about the same.
Sometimes smoke events can last for
weeks or (rarely) months. These longer events are usually punctuated by periods
of relatively clean air. When air quality improves, even temporarily, residents
should “air out” their homes to reduce indoor air pollution. People may also
wish to clean their residences during such reduced smoke intervals, including
damp mopping or dusting, and vacuuming (preferably with a high efficiency
particulate air [HEPA] filter-equipped vacuum), in order to reduce subsequent
re-suspension of particles that may have settled when the smoke was thicker.
An important drawback of advising
people to stay inside during smoke events is the increased risk of heat stress.
In many parts of the country, the fire season typically extends from mid-summer
through the early fall, when high outside temperatures are common. In homes
without air conditioning, in which individuals depend on open windows and doors
for ventilation, remaining inside with everything closed can be dangerous.
Older individuals and others in frail health run the risk of heat exhaustion or
heat stroke, which could have dire consequences. If outdoor temperatures are
very high, it would be prudent to advise those without air conditioning to stay
with friends or with family members who do, to go to a cleaner air shelter in
their community, or to leave the area. These and other options are discussed
Guidance on protecting workers in
offices and similar indoor workplaces from wildfire smoke has been developed by
the California Division of Occupational Safety and Health (Cal/OSHA), in
consultation with technical staff from several other California agencies. This
document (attached as Appendix A) addresses how to maximize the protection
provided by heating, ventilating and air-conditioning (HVAC) systems common in
public and commercial buildings, as well as other steps to protect occupants.