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Sep 11, 2023

Air conditioners help with wildfire smoke, right? Not necessarily. Here's why.

As much of the Eastern U.S. suffers from exceedingly poor air quality due to

As much of the Eastern U.S. suffers from exceedingly poor air quality due to plumes of smoke from Canadian wildfires, many wonder whether turning on their in-home air conditioners will help protect their lungs.

Experts have urged people to stay indoors to prevent health risks from the toxins that wildfire smoke contains. Still, the U.S. Environmental Protection Agency says some outdoor smoke can still seep its way into your home, polluting the air quality indoors.

A common myth is that air conditioners — specifically in-window units — bring outdoor air inside.

Instead, air conditioners recycle air already present inside a home. Refrigerants, fans and evaporator coils produce the cool air flowing from the air-conditioning unit.

Air conditioners are not air purifiers. But air-conditioner filters with a higher Minimum Efficiency Reporting Values rating can filter particles more efficiently than filters with low MERV ratings. Air purifiers can target the finest particles with the most efficiency.

Experts say some air conditioners can help protect against wildfire smoke entering your home by filtering out certain particles like dust, dirt, pollen and bacteria. But it depends on the type of air conditioner.

Portable air cleaners and central heating, ventilation and air-conditioning systems with High Efficiency Particulate Air filters are the best way to help protect against wildfire smoke.

An up-to-date filter with a high MERV rating or HEPA filter for your home's central air conditioning will enhance air purification. HEPA filters typically have a MERV rating between 17 and 20 and have a 99.7% efficiency rate of capturing particles in the 0.3-micron range, which is 1/25,000 of an inch.

Also see: Here's the Air-Quality Index of cities in the Northeast, Mid-Atlantic and Midwest as Canadian wildfires put many under air quality advisories.

Figuring out whether your unit has a fresh-air intake is critical for homes with a central heating, ventilation or air-conditioning system. If it does, read instructions on how to close the intake or turn on "recirculate mode." Also, ensure that the system is in good condition and placement.

Other air conditioners have a neutral effect if used properly, and experts advise against using some models at all.

For in-window air-conditioning units, figure out how to close the outdoor air damper during smoky conditions. It is also essential to check the seal between the window and the air conditioner's unit, ensuring it is as close-fitting as possible. If closing the outdoor air damper is impossible, the EPA advises that other cooling options, such as a fan, be considered.

Residents with portable air conditioners with two hoses should check the seal between the window vent kit and the window to ensure its security.

The EPA warns against using portable air conditioners with a single hose and evaporative coolers during smoky conditions, as these can "result in more smoke being brought inside." Consider other cooling methods, such as a fan.

Being well-versed in your type of air conditioner and its filter's condition is vital to preventing smoke infiltration into your home.

Read: Do smoky skies have you shopping for an air purifier? 5 things to know before you buy one

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