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Lessen Wildfire Smoke with your HVAC System

Wildfire smoke contains thousands of dangerous compounds, many of them toxic and small enough to enter your bloodstream. Hang with us as we walk through a few of the best ways to protect your home from wildfire smoke with your HVAC system. Whether you have central A/C or a heat pump, you’ll find tips to get cleaner air by using your existing system.


Wildfire smoke is a blend of gases and particles, including carbon dioxide, water vapor, carbon monoxide, hydrocarbons, and other organic chemicals, nitrogen oxides and trace minerals.

What is most worrisome is the particulate matter in smoke, tiny bits of ash and soot, much of it invisible to the eye. These tiny particles travel deep into the lungs and the smallest ones can even enter the bloodstream. The particles first damage the body simply by getting inside of it – triggering inflammatory reactions that themselves can trigger breathing difficulties, heart attacks and even strokes. Within a few days of smoke exposure, damaged lungs can succumb to bronchitis or pneumonia. In pregnant women, exposure to particulates has been associated with premature birth and low birth weight in infants.


People who have heart or lung diseases, chest pain, or asthma are at higher risk from wildfire smoke. Older adults are more likely to be affected by smoke. Children are more likely to be affected by health threats from smoke. Children’s airways are still developing and they breathe more air per pound of body weight than adults. Also, children often spend more time outdoors engaged in activity and play.


Avoid making your indoor air worse. Start by shutting your windows and doors if you’re advised to stay inside. Then avoid activities that increase indoor pollution, like smoking, burning candles, and using a gas stove. You’ll also want to limit your vacuum use (unless you have a vacuum with a HEPA filter) to avoid stirring up particles that are already inside your home.

If you don’t have air conditioning and you depend on open windows and doors for ventilation, it can be dangerous to shut yourself inside. There’s an increased risk of heat stress. Older people and others in frail health are more likely to experience heat exhaustion or heat stroke, both of which can have serious consequences. We strongly recommend air conditioning for hot days when you’re advised to stay inside. If air conditioning isn’t feasible for you at this time, it’s best to stay with friends, family or neighbors who have an AC system.


Make sure you have the right filter. Start by making sure you have a fresh filter for your system with a backup ready to go. To choose the right filter, consider the Minimum Efficiency Reporting Value (MERV) rating. Filters that are MERV 13-16 are expected to reduce indoor particulates as much as 95%. Filters with a High Efficiency Particulate Air (HEPA) rating, (or MERV 17-20) will reduce particulates in your home even more. If you have a ductless heat pump, we recommend a two stage catechin filter, which traps particulates as well as germs, bacteria, and viruses in your home.

Circulate and filter air through your HVAC system. If you have a cooling system, like central air conditioning, a heat pump, or a ductless heat pump, simply use your system as you normally would. By default, these systems re-circulate air in the home, so they filter air without pulling in additional particulates from outdoors. If you have a heating system, like a gas furnace, or a cooling system that you’re not currently using, we recommend turning the fan on at your thermostat. This will re-circulate air and help to filter out particulates.


Wildfire smoke should be taken seriously, especially for sensitive populations.  It’s important to pay attention to the quality of the air near your home. When you’re advised to stay indoors, keep the windows and doors shut and avoid doing things that make air quality worse, like smoking or burning candles.

If you have a central air system, make sure you have a fresh air filter with a high MERV rating, and keep a spare ready to go. You can filter air in your home by running your cooling system (AC, heat pump, or ductless heat pump). If you have a heating system (gas furnace) or a cooling system you’re not currently using, turn the fan on at your thermostat.