Preparing For Wildfire Smoke

Stay Safe This Summer

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 and to have a plan in place for your household.

Familiarize yourself with AirNow.gov. When you're advised to stay indoors, keep the windows and doors shut and avoid activities that make indoor air quality worse.

If you have a central air system, make sure you have a fresh air filter with a high MERV rating. 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, filter air by turning the fan on at your thermostat.

Who’s at risk

Prolonged exposure to wildfire smoke is a health risk for all populations. Groups at especially high risk include:

  • Those with heart or lung conditions
  • Older individuals
  • Children. 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.

Who’s MERV?! And why’s everyone talking about them?

The Minimum Efficiency Reporting Value (MERV) rating measures how effectively an air filter does its job. MERV ratings run from 1 (the least filtration) to 20 (the most filtration).

For an everyday filter in a residential HVAC unit, a MERV 11 is recommended. A MERV 11 filter strikes the right balance between cost and performance. Cost can rise quickly for higher filtration filters.

Wildfire season demands a filter with more filtration. MERV 13 to 16 filters will reduce indoor particulates as much as 95%.

While using a high MERV rating filter can help improve indoor air quality, keep in mind:

  • A filter is not a set it and forget it solution.
  • Filters need to be used in combination with other best practices to limit smoke entering the home.
  • High MERV rating filters can strain your home’s HVAC system (and are not energy efficient). Keep them on hand to use during an event, but not as your primary filter.

Make a date with you HVAC system and get to know each other

Knowing how to operate and maintain your HVAC system or air conditioner will help you be ready to keep smoke out once it arrives.

  • If you have a central HVAC system, find out if it has a fresh air intake. If it does, find out how to close it or turn the system to recirculate mode.
  • Make sure the HVAC filter is in good condition, fits snugly in the filter slot, and is replaced as recommended by the manufacturer. Consider upgrading to a MERV 13 or higher rated filter if your system can accommodate it.
  • Familiarize yourself with the thermostat settings. Find the Fan Mode, and if available, the option to Recirculate. 
  • If you have a window air conditioner, find out how to close the outdoor air damper. If you cannot close the damper, consider preparing other cooling options like a fan. Make sure that the seal between the air conditioner and the window is as tight as possible. Consider replacing the side panels with rigid foam board secured with easily workable rope caulk.
  • If you have a portable air conditioner with a single hose, typically vented out of a window, do not use it in smoky conditions. Consider other cooling options like a fan or window air conditioner. If you have a portable air conditioner with two hoses, make sure that the seal between the window vent kit and the window is as tight as possible.

Reduce Wildfire Smoke indoors using your HVAC system

You can circulate and filter air through your home’s HVAC system once you install the proper filter.

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, you can turn the fan on at your thermostat. This will re-circulate air and help to filter out particulates.

  • Prepare now by ordering an extra air filter or two:  Don’t wait until the smoke starts!
  • Be sure to get the right size by checking the air returns in your home and the filter in your HVAC unit.
  • For wildfire smoke look try to get a MERV 13 filter.

If you don’t have an option to run the fan on your HVAC system, consider an air purifier for extra filtration. These can be expensive (they run from a few to several hundred dollars) but can provide HEPA rated filtration.

Best Practices During a Wildfire Smoke Event

  1. Use AirNow.gov for real time air quality updates.
  2. Maintain good indoor air quality by avoiding smoking, burning candles or incense; running a gas stove or frying/broiling any food; limit any vacuuming, or spraying of aerosol products.
  3. Avoid strenuous activity to reduce how much smoke you inhale
  4. Use your HVAC system to circulate and filter air. Once you install a MERV 13 air filter, use your central air conditioner or heat pump as normal. If you don’t have air conditioning just turn on the fan at your thermostat to circulate air through your filter and your home. 
  5. Check your home for large air gaps and holes:  If you use window air conditioners, replace the plastic side panels with pieces of rigid foam board secured with easily workable rope caulk.
  6. Consider temporarily covering the bathroom fan, fireplace opening, mail slots and any other features open to the outdoors during times of heavy smoke.
  7. Make an evacuation/relocation plan. At-risk groups should make a plan for where they might stay, for example, with friends or relatives, if smoke levels are high and predicted to remain high. Organizing important items ahead of time, including financial and personal documents, will speed evacuation in case it becomes necessary.
  8. Protect pets: Your patients can reduce pets’ exposure to smoke by including them in planning. See the Wildfire Guide factsheet Protect Your Pets from Wildfire Smoke (PDF) .
  9. Develop a disease management plan: Patients with heart or lung disease should know: the symptoms of disease exacerbation, medications that can help, and when to call or come in for medical attention. Patients with asthma should have an asthma action plan.
  10. Stock up on medications and food: Having several days of medications and food on hand will help your patients avoid having to go outside during a smoke event.

What If I Don’t Have Air Conditioning

If 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 which can have serious consequences. Monitor the forecast and the indoor air temperature.

Experts recommend air conditioning for hot days when you're advised to stay inside. If air conditioning isn't feasible for you, it's best to stay with friends, family or neighbors who have an AC system.