Should I run my HVAC system during a wildfire?

AC unit in Burbank, CA

Wildfires are becoming extremely common in California, and it seems that every year now we have at least a few massive fires. All of these fires put off a huge amount of smoke that can have a dramatic impact on air quality. This air quality problem isn’t just limited to the outdoors, as the smoky air and ash can seep into buildings and result in poor indoor air quality as well. With the recent uptick in major wildfires, one question we have been getting from our customers more and more often is whether they can still run their air conditioning when the air outside is smoky. The answer to that question is yes, and here are the reasons why.

Why AC Is Safe to Use During a Wildfire

It is not only safe to run your air conditioner during a wildfire, but it is actually recommended. The one thing you shouldn’t do when the air outside is smoky is to leave your windows or doors open. Even if the weather is mild, all of that smoke will enter the house through your open windows and doors and reduce your indoor air quality. This is why you should always keep your AC running and your home sealed tight whenever there is smoke in the air.

One common misconception many people have about central air conditioning is that it draws air in from outside, and this is the reason that many people think they should turn off their AC on smoky days. The truth is that no matter how long your run your air conditioning, you never have to worry about it causing smoke to get inside your home. You also don’t need to worry about running a heat pump as they work the same as central AC units.

Central air conditioning works using the process of heat exchange. The AC compressor pumps refrigerant into the evaporator coil inside the home. The blower fan pulls air into the ductwork and forces it over the cold evaporator coil where the refrigerant then absorbs heat from the air. This raises the temperature of the refrigerant, and the hot refrigerant is pumped back out to the compressor where the heat is then released outside.

Evaporative Coolers, Portable ACs and Window Units

While heat pumps and central air conditioners are perfectly fine to use in smoky conditions, the same is not always true for evaporative coolers or portable and window air conditioners. Evaporative coolers, also known as swamp coolers, should never be used when it is smoky outside as they do draw air in from outside. If you use your evaporative cooler in smoky conditions, the air inside your house can quickly become as smoky as the air outside.

Most window air conditioners don’t draw air in from outside—although some do to provide ventilation. If the unit does draw in outside air, you can usually turn this feature off. On older units, you may need to close the outdoor damper to keep it from drawing air in from outside. If you do decide to keep using your window AC when it is smoky outside, you need to make sure that there is an airtight seal between the unit and the window to prevent smoke from seeping inside.

Portable air conditioners are generally always a bad idea to use during smoky weather, and this is true for both single- and dual-hose units. Dual-hose units utilize one hose to vent air out of the building and another hose to draw air from outside into the unit. If you run this type of unit when it is smoky, it will draw all of the smoke inside just like an evaporative cooler would.

Single-hose units don’t take air from outside, but some smoke can still get into the building through the exhaust hose. Still, the bigger issue with this type of portable air conditioner is that it creates negative air pressure inside the room. When the unit runs, it is constantly pumping air from the room outside. When the pressure inside is lower than it is outside, the smoky outdoor air will be drawn into the building through any cracks or air gaps in the home in order to balance out the pressure.

How to Overcome Indoor Air Quality Issues Caused by Smoke

Even if you keep your windows and doors shut whenever it is smoky, there is simply no way to prevent some smoke from getting inside. Every time you open the door, some smoke will enter. Smoky air will seep in through any air gaps in the building such as around your windows and doors or even through your walls or roof. This problem is known as infiltration, and it can be especially pronounced in older homes as they tend to have many more air leaks and drafts. Mechanical ventilation, such as running your kitchen or bathroom exhaust fans, can also increase the amount of smoky air being drawn into your home.

While you can’t fully stop smoky air from getting inside, there are steps you can take to make sure it doesn’t have a major impact on your indoor air quality. You should change your HVAC air filter much more often during wildfire season to ensure it continues to effectively filter smoke out of the air circulating through your home.

You may also want to consider upgrading to a higher-rated filter, as it will be more effective at filtering smoke and ash particles from the air. A basic residential air filter can only trap larger particles like dust and pollen, which means most of the smoke will go straight through it. However, a MERV 10 or MERV 12 filter should be sufficient to filter most of the smoke and ash inside your home.

Portable air purifiers are another decent option for overcoming indoor air quality issues caused by smoke. An even better option is to have a whole-home air filtration system installed. There are a wide variety of different whole-home air purifiers and filtration systems available that provide an extra level of filtration and protection.

These units are far more effective than even the best residential HVAC filter and are by far the best option for improving your home’s indoor air quality. Not only will they filter out smoke from the air, but also most other airborne pollutants and allergens. This includes mold spores, pollen, pet dander, dust mites, exhaust fumes and most volatile organic compounds (VOCs).

Expert HVAC and Indoor Air Quality Services

If you are concerned about the impact wildfires are having on your home’s indoor air quality, the IAQ experts at Air Max HVAC are here to help. We can perform an indoor air quality audit to determine what specific issues you’re facing and the best way to overcome them.

Our HVAC technicians install, repair and maintain a wide variety of IAQ equipment including air purifiers, air filtration systems, humidifiers and dehumidifiers. We can also inspect, maintain and repair your air conditioning system to help you stay cool. If you’re looking for an alternative to your window or portable AC this wildfire season, we also specialize in central AC installation.

We have locations in Burbank, Beverly Hills, Thousand Oaks and Mission Hills, and we serve customers throughout the LA area. If you have any questions about our IAQ services or need to schedule an AC service appointment, give us a call today.