As we wrap up our series on protecting our health during wildfire season, we need to review one last thing: air purifiers. Staying indoors and sealing your windows and doors will help with indoor air quality, but only an air purifier will provide the air filtration needed to keep you and your family safe.
And air purifiers aren't just needed during wildfire season.
At baseline, indoor air is much more toxic than outdoor air due to dust, allergens, and other chemicals.¹ But by using the right air purification system, you can drastically lower your exposure to harmful indoor pollutants.
In this guide, we’ll break down exactly why you need an air purifier, what you need to know about the different air filters, and how to choose the best air purifier and filters for your home and health needs.
Why Do You Need An Air Purifier?
When we think of air pollution, we usually think of outdoor air that's near factories or chemical plants. But the reality is that indoor air is ten times more toxic than outdoor air.¹
Both indoor and outdoor air contain pollutants that are harmful to human health. One of the main types of pollutants we want to remove from indoor air are particulates. Particulates are microscopic solid and liquid particles that are found in the air.² Because of how small particulates are, they can easily travel into the lungs and into the blood stream.
Particulates cause inflammation and immune system dysregulation. Additionally, breathing in particulates is linked to many different health problems like:³
Lung cancer
Chronic obstructive pulmonary disease (COPD)
Poor lung function
Asthma
Pneumonia
Heart attack
Stroke
The other main reason we need air purifiers is to remove chemicals, VOCs (volatile organic compounds), and odors from the air. These types of substances are also harmful to health.
Where Does Indoor Air Pollution Come From?
Indoor air pollution comes from an accumulation of particulates, solvents, and VOCs. Here's a breakdown of where these different pollutants come from:¹
-
Sources of Particulate Exposure
Moldy or water-damaged areas
Wildfire smoke
Tobacco smoke
Dust
Pollen and other outdoor pollutants
Pet dander, fur, hair
Wood burning fireplace/stove
Sources of Solvents and VOCs Exposure
Recent renovation/construction
Vinyl flooring/new carpet
Spray foam insulation in walls
Gas powered tools/mowers
Gas stove, oven, and/or furnace
Gas or wood stove/fireplace
Memory foam mattress or pillow
Cannabis smoke or vape
Cigarette smoke or vape
Air fresheners/candles
Furniture paint or refinishing
Standard/scented cleaning products
-
Sources of Particulate Exposure
Moldy or water-damaged areas
Wildfire smoke
Sources of Solvents and VOCs Exposure
Auto shops/gas stations
Hair/nail salons
Airports/airlines
Furniture and bedding stores
Construction sites
Dry cleaners
Places that use disinfectants (hospitals, dental offices)
-
Sources of Particulate Exposure
Open fields
Golf course
Agriculture
Busy streets, especially with truck traffic
Sources of Solvents and VOCs Exposure
Heavy traffic, especially trucks
Dry cleaners
Chemical plants
Industrial plants
Airports
What Does an Air Purifier Do, and How Do Air Filters Work?
An air purifier is a device that's designed to filter the air inside your home. These devices work by pulling in polluted air, passing the air through one or more filters, and releasing clean air back into your home.
Having an air purifier during wildfire season is crucial because harmful particles from wildfire smoke can easily get into your home--even with your windows closed and sealed. And even when it's not wildfire season, air purifiers are important to have as they filter out many pollutants we encounter on a daily basis.
So when it comes to picking out the best air purifier, the first thing to consider is the filter that's going to be used. There are two main options, and many people need both. These air filters include HEPA filters and activated carbon filters.
How HEPA Filters Remove Airborne Particles
A HEPA (high efficiency particulate air) filter is a type of air filter that removes particulates from the air. This type of filter is the most important when it comes to clearing substances like:¹
Wildfire smoke
Mold/mycotoxins
Pollen
Bacteria
Viruses
HEPA air filters are essentially all the same and work quite well at filtering out particulates. In fact, HEPA filters will remove 99.97% of particles sized 0.3 microns. This is the most difficult size particulate to remove from the air, and HEPA filters do a fantastic job at this. HEPA filters have to be replaced less often–usually once every six to 12 months.
How Activated Carbon Filters Improve Indoor Air Quality
The other filter to make sure an air purifier uses is an activated carbon filter. This type of filter is especially important for people with sensitivities to chemicals, mast cell activation syndrome, chronic health issues, and exposure to VOCs.
These filters contain activated carbon and other minerals called zeolites that absorb and trap toxins including:¹
Airborne chemicals
VOCs
Gases
Odors
Unlike HEPA filters, not all activated carbon filters are made equally. The more carbon the filter includes, the better it will work and visa versa. A filter containing at least three pounds of carbon is preferred.
Once the activated carbon filter is full of pollutants, it won't work anymore and has to be replaced. On average, you have to change this filter every three to six months.
Does the Strength of Air Purifiers Vary?
Just like the quality of filter used, the strength of air purifiers can vary. The strength and quality of air purifiers is measured by two factors: air changes per hour (ACH) and clean air delivery rate (CADR).
ACH is a measure of how many times per hour the air circulates through the air purifier. So the higher the number, the more pollutants are removed from the air. A score of five to six will reduce pollutants by 50%, and a score of eight to 10 will reduce pollutants by 80%.¹
CADR tells us how much clean, filtered air an air purifier can produce. So a unit with a higher CADR rating will clean the air faster than a unit with a lower CADR rating. It's important to note that not all air purifiers have CADR ratings–especially units that are higher-end or medical grade.¹
What Rooms in Your Home Need an Air Purifier?
The National Association of Environmental Medicine (NAEM) recommends that each primary room in your home have an air purifier. This includes rooms like your:
Bedroom
Living area
Kitchen
These primary rooms should have a filter with both a HEPA filter and an activated carbon filter that contains at least three pounds of carbon.¹ If you choose to filter other rooms in your house, you can use an air purifier with a HEPA filter and a standard carbon filter.
But during wildfire season, it's best to close off rooms in your house that you don't use so that air purifiers are able to better filter the air that you're regularly breathing in.
How to Pick Out the Best Type of Air Purifier For You
1. Measure the Size of the Area You Want to Purify
The first step to picking out an indoor air purifier is to figure out the size of the area that needs to be purified. The way to do this is to multiply the length of the room by the width to get the square footage. This number is what you'll use to determine the type and size air purifier you'll need.
It's also important to consider the ceiling height of each room. Rooms with ceilings higher than eight feet need a more powerful machine to filter air from all parts of the room. The same idea goes for homes with open floor plans. You may need to consider a more powerful unit or multiple units to make sure all of the air is filtered.
2. Calculate the Clean Air Delivery Rate You Need
An air purifier's CADR tells you how quickly an air purifier can produce filtered air. According to Energy Star, it's best to find an air purifier that has a CADR of at least two-thirds the square footage of the space. This is based on rooms with an eight foot high ceiling. So rooms with ceilings higher than this will require an air purifier with a higher CADR.⁴
Here's a table to reference for determining CADR based on the square footage of a room:⁴
One other thing to consider with CADR is wildfire smoke. If you're going to be filtering wildfire smoke out of your home, you'll need to pick an air purifier with a higher CADR. The NAEM recommends a minimum CADR rating of 250.¹
3. Determine the Air Changes per Hour You Need
ACH is how many times per hour air circulates through the air purifier. The Environmental Protection Agency (EPA) recommends a minimum of 3.5 ACH.⁵ This number increases to 5 ACH for viruses and bacteria.⁶ So in general look for a unit with an ACH of at least 5, especially for use during wildfire season.
4. Pick Out Your Filters
HEPA filters are generally the same across all air purifiers. However, activated carbon filters vary significantly.
The strength of the activated carbon filter you choose will depend on how many chemicals and VOCs you're exposed to as well as your sensitivity to them. You can use the chart above to determine if you live in an area that gets exposed to VOCs.
If you're unsure of your risk to indoor pollutants, you can purchase or borrow an indoor air quality monitor to figure out your risk of exposure. Here are a few options of indoor air quality monitors to consider:
According to the NAEM, here's how to figure out which size activated carbon filter you need based on your risk and sensitivity to VOCs:¹
Low risk and no sensitivity: Standard (less than one pound of carbon) activated carbon filter that comes with air purifier is okay
Moderate risk and some sensitivity: Activated carbon filters with three to 12 pounds of carbon
High risk and strong sensitivity: Activated carbon filters with 12 to 30 pounds of carbon
For wildfire smoke, it's recommended to have an activated carbon filter with 12 to 30 pounds of carbon to make sure any VOCs are properly being filtered out of the air. Plus, wildfires can also expose your home to formaldehyde. So it's important to pick an activated carbon filter that includes zeolite or potassium permanganate, which are needed to filter out formaldehyde.¹
5. Figure Out Your Budget For Your Air Purifier and Filters
Once you know the type of air filtration unit you need to buy, the next step is to determine your budget. Air purifiers can range from $230 to $1000 depending on the unit's carbon filter life, CADR, and ACH rating. It's important to remember to factor in the cost of replacement filters which can range from $50 to $275 a year.
What are the Best Air Purifiers?
With all of the different air purifiers on the market, it can be difficult to pick one. Here are some units recommended by the NAEM that I often recommend to many of my patients.
Best Medical Grade Air Purifiers
For people requiring higher levels of VOC filtration, a medical grade air purifier is the best option. While they're more expensive than other options, they're the most efficient at air filtration.
The types of medical grade air purifiers recommended are Healthmate and Healthmate Plus by Austin Air and HealthPro Plus by IQ Air. All units filter large spaces ranging from 1125 to 1500 square feet. Austin Air purifiers contain larger activated carbon filters compared to IQ Air purifiers.
Note that the Healthmate Plus and the HealthPro Plus have the option to include potassium permanganate in the filters which is needed to filter out formaldehyde from wildfire smoke.
Another difference between these two brands is that the HealthPro Plus model by IQ Air includes an air quality monitor and an indicator that will notify you when filters need to be replaced.
Best Affordable Air Purifiers
If you don't need a medical grade air purifier and need something more budget-friendly, I recommend the Blue Pure 311iMax or Blue Pure 211iMax by BlueAir. The 311iMax filters up to 929 square feet while the 211iMax filters up to 1524 square feet.
Both units contain HEPA filters and have CADR ratings of at least 250, but they have smaller carbon filters. So these models are ideal if you're not exposed to VOCs or if you're looking for an air purifier to use in a low-traffic room in your house. Plus, they both have air quality monitors and indicators to tell you when filters need to be replaced.
Another company that many of my patients like to use is The Air Doctor. I have one of these myself and really feel like it’s a good quality air purifier.
Tips for Using an Air Purifier
Once you've picked out your air filtration system, there are some other things you should do to make sure it's running well. Here are some tips:
Position air purifiers at least 18 inches from walls and furniture
Make sure there's strong air flow around your unit when it's running
Keep windows and outside doors closed as much as possible
Clean your system's pre-filters once a month to remove pet hair and dust, as this can make your air purifier not work as well
Keep track of when you need to change the filters in your unit
For day-to-day use, run your air filters 24/7 on their highest "quiet" setting. For events like wildfires that cause higher levels of pollution, you can turn the unit on high.
Do You Need Help Picking Out Your Air Purifier and Filters?
Choosing the right air purifier and air filters can make a big difference in your health and well-being—especially if you’re sensitive to pollutants or live in an area affected by wildfire smoke. With so many options on the market and a wide range of features, it’s easy to feel overwhelmed trying to find the best fit for your home.
One of my favorite websites to recommend that patients visit is Allergy Buyers Club. They have a really easy-to-use search engine on their website. They don’t have all of the air filters that we discussed today, but they do have most of them.
References:
1. NAEM Air Filtration Guidelines – (envmedicine.com)
2. Particulate Matter (PM) Basics – (epa.gov)
3. Efficacy of HEPA Air Cleaner on Improving Indoor Particulate Matter 2.5 Concentration – (nih.gov)
4. How to Choose a Room Air Cleaner – (energystar.gov)
5. How much ventilation do I need in my home to improve indoor air quality? – (epa.gov)
6. Preventing the Spread of Respiratory Viruses in Public Indoor Spaces – (epa.gov)