Indoor Air Quality & Wildfire Smoke

2023 has been a year of unprecedented wildfire activity across Canada, with winds carrying smoke and ash into populated areas from coast to coast. The resulting reduction in air quality has many people concerned about how to protect themselves and their families against the harmful effects of wildfire smoke and airborne particulates. It’s essential to keep the air in your home as clean as possible, so here are some valuable tips you can use to reduce potentially harmful airborne particles and wildfire smoke in your indoor living spaces.

Wildfires in Canada unfortunately happen every year due to accidents, careless campfires, and lightning strikes. However, this year has seen a tragic series of coincidences that have resulted in numerous simultaneous wildfires of varying degrees in almost every province and territory in Canada. The main contributing factor for the marked increase in wildfires so early in the year is shifting weather patterns that have produced a drier-than-normal spring season, making it incredibly easy for lightning strikes in remote areas to quickly spark wildfires that grow rapidly out of control.

As if this weren’t bad enough, the wind patterns have been carrying the smoke, ash, and airborne particles created by the wildfires over populated areas, causing widespread air quality concerns in many cities. In fact, certain areas of the country have been so affected by the smoke that emergency alerts have been issued advising people to avoid outdoor areas and protect themselves from the dangers of wildfire smoke inhalation. Certainly, the danger is real, as wildfire smoke contains many elements that are harmful if inhaled.

What Do Wildfires Put into the Air as They Burn?

Simply due to the wide variety of organic material that exists in a typical forest, wildfire smoke can contain a diverse range of gasses, chemical compounds, and tiny particles. For example, carbon monoxide, hydrocarbon pollutants, ash, mold spores, sulfuric acid, and soil particles are just a few of the numerous different things that can be found in wildfire smoke and carried through the air into populated areas. All of these things can have varying effects on the human body, from mild irritation and coughing, to severe allergic reactions and life-threatening respiratory problems.

Now, it’s important to note that the air we breathe indoors and outdoors will always have trace amounts of airborne particles and pollutants in it. However, these are typically in such low concentrations as to not be a major concern for most people. In addition, the air in our indoor spaces is usually filtered by HVAC systems, helping to reduce the concentration of airborne contaminants in our homes and workplaces. When wildfires burn and release smoke into the air, the concentration of these particles and pollutants increases exponentially and reaches levels that can be severely harmful if inhaled.

How Often Should I Change My Furnace Filter During Wildfire Season?

Once wildfire smoke reaches populated areas, it’s impossible to completely prevent it from entering indoor spaces. Our homes are not designed to be air-tight, and as doors and windows are opened and closed there will be exchanges of indoor and outdoor air that take place, allowing wildfire smoke and the particles it contains to enter our living spaces. It’s advisable to keep windows and doors closed as much as possible to minimize this. Furthermore, you’ll also want to set your HVAC system to recirculate air continually, even when the system is not heating or cooling. This will work to continually filter the air in your home and reduce the concentration of harmful particles from wildfire smoke.

This continual state of air recirculation will cause your furnace filter to load up at a faster rate than if it was operating in its normal intermittent mode. As captured particles eventually build-up in the filter, air resistance will increase and the life of the filter becomes shorter. This is normal, but the accelerated rate means that it’s important to change your furnace filter more regularly in order to maintain optimum air quality and energy efficiency of your HVAC system.

The exact interval of furnace filter changes under normal operating conditions depends on several factors, which we explain in detail in our Guide to Filter Change Frequency. Simply put, deeper filters (4”, 5”) will have greater capacity than thinner filters (1”, 2”). This means the thicker the filter, the longer you can go in between filter changes. As a general rule of thumb, 1” and 2” filters should be changed once a month for best performance, while thicker filters can last from 3-6 months or more between changes. However, with the increased amount of contamination in the air from wildfire smoke, these intervals should definitely be shortened.

To begin with, if you are in an area that has been or is currently affected by wildfire smoke, we strongly urge you to check the state of your existing furnace filter to see how dirty it might already be. Even short time of filtering out wildfire smoke can accumulate a great deal of particulate in the filter. Upon inspection, if the filter appears dark, dusty, and generally dirty in appearance, then it’s time for a change. Afterwards, make a note or set a reminder for yourself to check the filter on a weekly basis as long as the air quality warnings are in effect. This will help ensure you are aware of how dirty the filter is getting, and allow you to plan for the next filter change to keep the air in your home as clean as possible.

What Furnace Filter is Best at Removing Smoke & Particulate?

Filtering out tiny particles from the air is the main purpose of your furnace filter, but not all filters will do this with the same degree of effectiveness. Each make and model of furnace filter is rated to a certain level of air filtration efficiency according to its Minimum Efficiency Reporting Value (MERV) rating. These values indicate how efficient the filter is at capturing airborne particles between 10 microns and 0.3 microns in size. The higher the rating, the greater the filter's ability at capturing and retaining tiny particles. To get the full story on MERV ratings and what they mean, check out our Guide to Furnace Filter MERV Ratings.

Most standard furnace filters are rated at a 7 or 8 on the MERV scale. At this level of efficiency, the filter will be generally effective at capturing common household dust and airborne particles such as pollen, pet dander, and mold spores. Furnace filters with MERV ratings of 10 or higher are often branded as allergy control filters due to their increased ability to capture allergens, making them a better choice for homes where people may have allergy sensitivities or respiratory concerns. The highest-efficiency furnace filters can go up to 16 on the MERV rating scale.

Overall, with a furnace filter rated somewhere between MERV 10 and MERV 13, you can be confident it will be able to efficiently capture the vast majority of airborne particles produced by wildfires, and improve the overall cleanliness of the air inside your home. While most furnace manufacturers recommend a rating of no more than MERV 13 to ensure proper operation of the unit in terms of airflow and energy efficiency, you could utilize filters up to MERV 16 for short periods when the threat of forest fire smoke in your local area is at its worst.

In regards to removing lingering odours of smoke from the air, you should check to see if your furnace can be equipped with a filter that features activated carbon. These filters utilize the porous surface of carbon molecules to attract and hold onto odour-causing compounds, removing them from the air and leaving it clean and fresh smelling. Alternatively, if there is not a carbon furnace filter that is compatible with your model of furnace, you may wish to utilize a standalone air purifier unit to help remove lingering smells and odours brought into your home by wildfire smoke. While operating, these units continually scrub the air in your indoor spaces, removing extremely tiny particles as well as odour molecules.

Additional Wild Fire Information

Here are a few useful sites to keep an eye on the Canadian wildfire situation as things progress over the summer of 2023.

• Ontario Interactive Fire Map
• Canadian Interactive Fire Map
• US and Canada fire map and data. NASA | USFS
• UBC The Weather Forecast Research Team 

Change Your Furnace Filter Now to Remove Smoke Particles

If wildfire smoke has been present in your area, or is threatening to be carried into your area by wind currents, now is the time to ensure your HVAC system is equipped with a fresh, high-efficiency filter. By taking steps to protect your home with fresh, filtered air, you can reduce the risks posed by airborne particles produced by wildfires. This will help you and your family breathe a little easier during these difficult times. Thanks for taking the time to read this important information. We encourage you to share it with friends and family for their benefit as well. We’re all in this together. Take care now!