How to Safely Run Your Air Conditioner During Wildfire Smoke Events

Canadian wildfire smoke blanketed a massive section of the United States on Friday, forcing millions to seek shelter indoors. Residents from the Midwest to the East Coast scrambled to protect their lungs as hazardous air quality persisted. One critical question emerged: Is it safe to run the air conditioner when outdoor air turns toxic?

Environmental Protection Agency officials urged people to take protective measures by considering portable air cleaners or high-efficiency HVAC filters. They also recommended using N95 respirator masks to limit smoke inhalation and adjusting HVAC systems or air conditioners to safer settings. The answer to whether AC use is safe depends entirely on proper configuration, according to medical experts.

“I would try to set your air conditioning on recirculate so that you’re not breathing in as much of the outdoor air, and if you have good level filters on your air conditioner, make sure that they’re in place and that you’re using them,” Dr. Brian Christman, a professor of medicine at Vanderbilt University, told Nexstar’s WJW.

Understanding How Air Conditioners Work During Smoke Events

Most air conditioning units operate by cooling the air inside the house and recirculating it, not pulling in air from outside. This fundamental design makes them generally safe during wildfire smoke events. However, some units feature a fresh air function that can compromise indoor air quality during hazardous conditions. Dr. Christman emphasized that running air conditioning remains acceptable as long as users select the right settings.

Window AC units primarily recirculate indoor air, but certain models include fresh-air vents or outdoor air dampers. Cole Goldklang, founder of Breasy, which rents and installs AC units in New York City, explained that users should check for a small lever on the side of their units. Identifying and closing this fresh air intake prevents outdoor smoke from entering your home.

The hazy conditions transformed even routine activities into health concerns. The sun hung red in the sky as New Yorkers searched for respite from the smoke invading their lungs. Getting inside wasn’t always enough, as poorly configured cooling systems continued drawing contaminated air indoors. The city’s air quality index remained at “moderate” or “unhealthy for sensitive groups” throughout Friday.

Critical EPA Recommendations for Indoor Air Protection

The Environmental Protection Agency provided specific guidance for maintaining clean indoor air during smoke events. First, residents should determine whether their system has a fresh air intake mode and ensure it remains set to “recirculate” instead. The agency stressed that filters must be in good shape for optimal protection. Users should consider upgrading their filters if their HVAC system can accommodate higher-rated options.

Evaporative coolers present a particular challenge during smoky conditions. The EPA advised against using these devices during wildfire smoke events because they draw more contaminated air inside. Fans and window AC units serve as better alternatives when air quality deteriorates. Property owners using window units must ensure a proper seal between the unit and the window frame to prevent smoke infiltration.

The agency also recommended keeping windows and doors closed throughout smoke events. Using air conditioning instead of opening windows for fresh air represents a generally sound strategy when outdoor air quality becomes hazardous. This approach maintains cooler indoor temperatures while minimizing exposure to harmful particulates.

Essential Maintenance Steps During Hazardous Air Quality

Goldklang highlighted a crucial aspect of routine AC maintenance that many people neglect. Users should rinse AC filters with water and replace them every four to six weeks. Every few years, owners need to purchase new filters from hardware stores or online retailers. This maintenance becomes especially important during extended periods of poor air quality.

Several warning signs indicate when filters require immediate attention. If your AC makes unusual noises, fails to cool effectively, or drives electricity bills unexpectedly high, check the filters right away. Most AC systems include a light or other alert mechanism to remind users about filter maintenance. Even aging AC units can perform well if properly maintained, according to Goldklang.

Proper installation and sealing also play vital roles in preventing outdoor air infiltration. Window AC units feature “accordion arms,” those side panels designed to fill gaps between the unit and window frame. Goldklang suggested purchasing foam and placing it on the indoor portion of that space to insulate the area better and reduce outside air entry. The EPA echoed this advice, urging users to remain mindful of any gaps around windows that could allow contaminated air inside.

Weekend Smoke Forecast and Expected Conditions

The wildfire smoke parked over a large swath of the country on Friday. It brought hazardous air quality from the border near Minnesota down to D.C. Nexstar meteorologist Blake Matthews explained that the smoke would likely linger for the next 24 to 48 hours for many areas. Storms and rain were expected to help clear the air afterward.

Thick smoke hung around through Friday afternoon and evening from Minnesota down into Wisconsin and Michigan, over toward Chicago, through Pennsylvania and down into Virginia and D.C. The densest smoke for Friday night concentrated near the Ohio-Pennsylvania border, as well as in parts of Virginia, West Virginia and Maryland.

A trough of low pressure was scheduled to arrive Saturday, bringing relief for many affected areas. Showers and thunderstorms were forecast across New England and down into the mid-Atlantic, moving smoke out of the way. Matthews expected the smoke to move up into Boston by Saturday afternoon and eventually into Maine as the day closed out.

Long-Term Air Quality Concerns and Uncertainty

If rain successfully clears out the smoke on Saturday, residents could continue to enjoy benefits on Sunday. However, uncertainty remains about when the next wave of smoke will arrive. Even if winds from the northwest clear skies temporarily, smoky air could keep returning until firefighters extinguish the blazes. This pattern might continue for months, officials warned.

The ongoing nature of these wildfire events makes proper AC configuration and maintenance more critical than ever. Residents cannot rely on short-term weather patterns to guarantee clean air. Instead, they must implement lasting protective measures within their homes. The combination of closed windows, properly sealed AC units, clean filters, and correct recirculation settings offers the best defense against hazardous outdoor air quality.

Beyond immediate comfort, proper insulation and sealing delivers additional benefits. These measures help control utility bills by preventing warm air infiltration during summer months. They also reduce AC noise levels and improve overall energy efficiency. What starts as a health precaution during wildfire season transforms into year-round savings and comfort.