Does HVAC Filter Wildfire Smoke?

Wildfires devastate the air around it as it burns through the land. The smoke can make the air unbreathable, forcing many regions to post-stay indoors advisories. However, you may not be safe indoors either.

Wildfire smoke can leak into your home through your doors, windows, and vents.

Luckily, HVAC systems can filter out wildfire smoke, letting you and your family breathe. You will need the right filter setup, but you can make your home a haven from the hellscape outside. You can even build the filters yourself.

While HVAC systems can filter wildfire smoke, they cannot do everything. They only work well in conjunction with other measures you should implement as well.

By taking the right precautions for your area, you can ensure the air in your home is as clean as can be.

HVAC Filters Can Remove Wildfire Smoke

While most people worry that wildfires may burn down their homes, there is a more pressing matter.

A wildfire does not need to be near you to kill you. Its smoke can travel for hundreds or thousands of miles depending on the prevailing winds.

Consisting of fine particulates of wood, carbon, and other organic materials, smoke can get into your eyes and lungs where which can cause bronchitis and other inflammatory illnesses, runny nose, burning eyes, and other ailments.

They can also aggrieve heart and respiratory diseases as well.  Breathing smoke can even lead to premature death.

How Smoke Enters Your Home

Your best bet is to stay home when there is a wildfire smoke advisory in the area. However, you must make sure that it cannot seep indoors. The fine particles can pass through small gaps. 

Some common gaps smoke can pass through include:

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HVAC Systems Filter Wildfire Smoke by Design

To keep the smoke outside, you must ensure that there is no way for it to leak inside. That means sealing all windows and doors.

Luckily, you do not need to worry about your HVAC system, especially if you have an outside unit. 

HVAC systems are heat exchangers. No air passes through them. They use closed tubes of coolant to drive the heat to the outside.

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The units use fans to push air over these tubes, but the inside and outside air flows remain separate throughout the process.

Because of this, HVAC systems are safe to run even during the worst wildfire advisories. 

The only want smoke can pass through an HVAC system is through holes in the ventilation heading into your home.

In other words, the smoke will only get through vents that are not sealed properly or through the window around an in-window system.

You want to make sure that you turn off any setting that allows outside air to flow through.

Many HVAC units have a low-power fan mode which does just move air in and out of the home. Therefore, you must avoid using those modes during a smoke event. 

HVAC Remove Indoor Smoke with the Right Filter

While HVAC systems will keep the outside smoke from entering your home, but they cannot do anything on their own for the smoke that manages to break in through other means.

The normal air circulation just sends back the air out unaltered. Fortunately, most modern air conditioner units come with a built-in air purifier. 

The key HVAC air purification component is the air filter. Air filters come in all shapes, sizes, and materials, but they are all rated for certain levels of purification.

You can find cheap filters that can remove large particles but last only 30 days.

Other filters can also eliminate chemicals and odors while they completely remove the smoke for months. 

Types of HVAC Filters

With so much riding on the filter, you want the best one you can afford for your HVAC system.

The simple answer is to buy the best air filter on the market, but you may not need all the features.

You can save money by going cheap, but the filter may not do what you need.

Thus, a good understanding of the types of filters you can get will help you keep the smoke out of your house. 

  • High-Efficiency Particulate Air (HEPA): HEPA filters have the backing of the U. S. Department of Health as they produce 99.97% clean air, but they cannot remove odors, gasses, or fumes. They also require frequent replacements due to mold build-up. 
  • Ultraviolet (UV): UV filters can remove mold, bacteria, and viruses from the air, but they do nothing for wildfire smoke. They can also release ozone which can aggravate the adverse health effects of the smoke. 
  • Electrostatic: Available in reusable and disposable options, electrostatic filters can trap smaller particulates such as smoke, but they have issues with larger particles such as mold spores. 
  • Washable: You can save money with an environmentally friendly, reusable washable HVAC filter. They can remove most particulates from the air, but only if they are well-cleaned and dry. A damp filter can grow mold and mildew. 
  • Media: Low-maintenance HVAC media filters offer highly efficient filtration with great airflow. They require annual professional inspection and replacement though. 
  • Spun glass: A the most basic type of HVAC air filter, spun glass filters are very cost-effective and disposable. They protect your HVAC system from debris, but they are not particularly good at purifying the air. 
  • Pleated: Pleated HVAC filters offer decent filtration for airborne pollutants, but you need a highly pleated filter to keep wildfire smoke out of your home.  However, your air conditioner may overheat as these filters restrict airflow to function.

Generally, if you find yourself under a wildfire smoke advisory, your best HVAC filters are the media, HEPA, electrostatic, and pleated.

These filters are highly effective at removing smoke particulates from the air. 

Most of these filter types work with multiple HVAC models as well.

Therefore, you can save money by going with a low-cost filter for everyday use, and swap in a more efficient unit as environmental conditions deteriorate. 

General HVAC Tips During a Wildfire Advisory

With the right filter and setup, any air conditioner unit can keep you safe from the wildfire smoke outside.

With that said, you must use the right filter and setup to reap those benefits. If there are breaches, the smoke can and will make its way inside your home.

Choosing the filter is easy enough as you just need one that can sweep the fine soot. Most of your decision will be about price and any additional feature you may want. 

However, setting up your air conditioner correctly is what truly decide how well your unit screens out smoke.

To get you started, the American Lung Association and the Oregon Health Authority posted the following advice on how to use an HVAC system during a wildfire event to keep your indoor air healthy.

Stay Safe and Flee if the Approaches

Before you do anything else, if the fire is approaching you or the local authorities posted an evacuation order, you must leave immediately.

Your priority should always be the safety of you and your family. No HVAC unit can prevent your home from burning down.

You want to remain indoors as much as possible regardless. By reducing your exposure, you can keep yourself healthy while reducing the risk of letting the smoke inside.

If you must go outside, always wear protective gear such as an N95 or P100 respirator mask.

Close All Potential Leaks

Because HVAC units can block the smoke from entering your home on their own, you want to help them by closing shut all the other ways smoke can enter.

Thus, you want to shut all doors and windows as soon as you notice that there is an advisory in your area.

You may also want to lay a damp towel under your doors and around other crevices.  

Other potential leaks include bathroom fans and roof vents that lead outside. You want to turn these fans off and close the vents during a fire advisory. 

Maintain Your Indoor Air Quality

With your home shielded from the outside, you want to avoid inadvertently bringing in the smoke yourself.

That means washing anything that might have been exposed every time you walk in from the outdoors. 

You also want to avoid adding your smoke by using your gas oven, burning candles, or smoking.

You may also want to avoid vacuuming as well. These activities will aggravate the situation, especially if you do not have a highly efficient filter in your air conditioner. 

Change or Clean Your HVAC Filter Daily

Depending on the local air quality, you may need to clean your HVAC system more often than usual.

Therefore, you will want to inspect the filter daily and keep a supply of backups. You may also want to replace your filter with one more suited for the current levels of smoke in your area. 


As wildfires rage through the countryside, their smoke can travel for miles away from the leading edge of the flames.

The smoke can cause numerous health risks if you are unlucky enough to breathe it.

Fortunately, all properly configured HVAC units can keep the smoke out of your home by design. 

You still must lock down your home completely, but you can rest assured that your family will remain cool and safe as can be.

Just remember to use a good HVAC air filter to capture any smoke that gets behind your defenses. 

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