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Clean Air Advisory

Air Quality District Clean Air Room Advisory

Mendocino County Air Quality Management District and Mendocino County Public Health Department encourage Mendocino County residents to plan for poor air quality conditions caused by future wildfire smoke. Smoke and ash from wildfires contain very small particles known as particulate matter. These particles harm the lungs and heart, and can cause coughing, wheezing, difficulty breathing, chest pain, nausea, and in severe instances, premature mortality. People with heart or lung disease, seniors, kids, and pregnant women are especially sensitive to smoke.

Stay indoors for protection from wildfire smoke

The best protection against wildfire smoke is to stay indoors as much as possible when smoke is present. The following steps help to safeguard for your family to have safe indoor air quality.

Protect Against Wildfire Smoke by Creating a “Clean Air Room”

Choosing & Using an Air Purifier 

  • Pick a HEPA (High-Efficiency Particulate Air) purifier to reduce particulate matter indoors by 90 percent. These can be purchased at hardware stores or online retailers.
  • Make sure that the device doesn’t create ozone – find a list of safe options online:
  • HEPA purifiers come in various makes and models, suitable for different room sizes.
  • Use the purifier in a room where you spend a lot of time, like a bedroom.
  • HEPA purifiers for an average-sized bedroom cost approximately $75.
  • Check your windows and doors and make sure the room is sealed tightly so smoke from the outdoors does not get pulled inside.
  • Replace the filter as directed in the owner’s manual. Filters need to be replaced more frequently if used during a wildfire.

Do It Yourself construction of an air purifier

Making Your Own Air Purifier

  • Assembling a DIY version of an air purifier can be a more affordable option, with materials costing approximately $40.
  • This DIY version has been shown to reduce harmful particulate matter indoors similarly to a HEPA purifier.
  • Here’s how to make your own:
  • Use tape to attach a 20x20 MERV-rated air filter — like what you would use for your HVAC system — to the back of a 20”x 20” box fan. Attaching to the back of the fan creates a better seal.
  • Use a filter with a MERV rating of 13.
  • Check the filter for the direction of the airflow, marked on the side of the filter.
  • Check your windows and doors and make sure the room is sealed tightly so smoke from the outdoors is not pulled inside.
  • Replace the filter more frequently if used during a wildfire.
  • As needed, disassemble the box fan to wipe away any accumulated dirt.
  • For safety, follow these precautions:
  • Don’t leave the device unattended.
  • Turn off the device while sleeping.
  • When the fan is modified in this way, use the device as an air cleaner, not as fan to cool your home. 

Tips for indoor air quality

Minimizing Sources of Indoor Air Pollution 

  • In addition to using a HEPA air purifier, follow these recommendations:
  • If advised to stay inside, keep windows and doors shut and sealed tightly.
  • If temperatures are high and there is no way to keep the home cool with windows and doors shut, consider temporarily relocating to an area with better air quality until conditions improve.
  • Upgrade your filter in your HVAC system to a MERV filter, with a MERV rating of at least 13. Check with your HVAC professional to see what MERV rating your HVAC system can handle to ensure proper functionality. 
  • Do not smoke or burn firewood, candles, or incense in the house.
  • Use your range hood while cooking, especially when using a gas stove.
  • Consider using professional services for a blower door test to detect air leaks. This service can help you know how to properly seal your home.

During wildfires, there are various ways to stay updated on local air quality conditions:
Check hourly air quality conditions, daily air forecasts, and sign up to receive air quality alerts, at: For smoke, air quality and federal fires, visit

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