NorthWestern Energy continues their HEPA air cleaner REBATE for residential customers. 
Receive up to $100/unit if you purchase a new Energy Star HEPA air purifier (through at least July 2025).
Find the form HERE and note that the form states this only runs through June - we've been assured of this extension! 

THERE ARE 4 MAIN THINGS TO KNOW about HEPA AIR FILTERs!

This page serves as a guide to help you learn:
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1.   What a HEPA Portable Air Cleaner (PAC) is and how it works
2.   Which model of HEPA PAC to buy
3.   How and when to use your HEPA PAC
4.   When and where to replace your HEPA filter

Scroll down to find out more!

​Here's a short video with most of what you need to know when it comes to HEPA PACs.  Thanks Sarah Coefield!
WHAT IS A HEPA PORTABLE AIR CLEANER (aka HEPA PAC / HEPA air purifier)?
  • HEPA portable air cleaners (PACs for short), also known as air filtration units, are portable appliances that filter out really tiny particulate matter (PM) - 2.5 microns and smaller. These ultrafine bits are the most common and dangerous component of wildfire smoke, which is affecting Montana more frequently as our climate changes. It's the actual HEPA filter insert that captures the PM2.5. These need to be replaced at least once/year (see below)

  • HEPA PACs typically come with replaceable carbon pre-filters that also remove the Volatile Organic Compounds (VOCs) in wildfire smoke (benzene, acrolein, formaldehyde, etc.). Pre-filters also take care of larger particles such as pollen, pet fur, etc.  
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  • HEPA PACs are available for central heating and cooling systems as well, but here we talk exclusively about portable units that use replaceable filters and plug into a standard wall outlet. Click HERE for more about filters used in central heating and cooling systems.
Watch our demo to see how a HEPA air purifier cleans indoor air!
HOW DO I KNOW WHICH MODEL TO BUY?

Most importantly, make sure the unit uses a genuine HEPA air filter. Other filter types and air purification methods may not filter the smallest PM that causes the greatest health problems, and some release ozone gas - which isn't good for people or the planet!  If your unit has a "PlasmaWave" function, we recommend turning this off (it may emit a very small amount of ozone).  Avoid "HEPA-like" units! 

KEY CONSIDERATIONS:
  • TRUE HEPA. Make sure the PAC you choose is labeled HEPA, not HEPA-like. True HEPA PACs are able to filter out 99.7% of particles down to 0.3 um. Some units only filter down to 3 microns - which means they do NOT filter out smoke.
  • ROOM SIZE. Buy the right air filtration unit to fit the room where you'll use it most frequently. (We recommend the bedroom; see below.) Most units list the size room they can filter effectively. Others list a Clean Air Delivery Rate (CADR), in which case, choose a tobacco smoke CADR at least 2/3 the room’s area. For example, a 10’ x 12’ room (120 square feet) would require an air cleaner with a tobacco smoke CADR of at least 80.
  • ​NOISE LEVEL. Some units are noisier than others. If this is a concern, check user comments and feedback online.
  • ENERGY STAR RATING. To save energy and money on your electricity bill, choose units with the U.S. Department of Energy's Energy Star rating.
  • COST. Consider the factors above and purchase what you can afford. Look for sales and rebates!
HEPA PORTABLE AIR CLEANER RECOMMENDATIONS

There are dozens of HEPA PACs on the market. Buy units that filter PM as small as 0.3 microns and have an Energy Star rating.  Units are available online and at local hardware or appliance stores. Prices vary depending where you buy them.  To find the best HEPA filter for you, we recommend checking out this list of approved filters from the California Air Resources Board (CARB) HERE.
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HOW SHOULD I USE MY HEPA PORTABLE AIR CLEANER?

  • USE YOUR HEPA PAC IN YOUR BEDROOM AT NIGHT. This way your body gets a break while you sleep, and for most people, this is the longest period of time you'll spend in one room. For most of us, the portable nature of these units allow you to move them to a more central room during the day.  For people who cannot move their PACs, simply keep it in the room you spend the most time, with the doors open between rooms.
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  • HEPA PACs WORK BEST WHEN ALL WINDOWS AND DOORS ARE CLOSED. This is easy in the winter, but it can be more complicated with hotter weather during wildfire season. During hotter days, we generally recommend closing windows and blinds to keep your home cool, then opening them back up at night to draw in cool air. When it's both smokey and hot, this is difficult and the best thing to do is carefully assess the current air quality and balance that with the health risks from overheating.* This is especially a concern for the elderly. 

  • Heat is dangerous too. The EPA has guidance about how to balancing HEAT and SMOKE here . 
 
  • CHANGE YOUR HEPA FILTERS! This includes both the HEPA filter and the carbon pre-filter (removes volatile organic compounds - VOCs).  Both will become saturated with particles. See below for information about HEPA filter replacements!​​

HEPA FILTER REPLACEMENTS

WHY SHOULD I REPLACE MY HEPA FILTER?

HEPA filters accumulate residue over time. During wildfire smoke season, they capture more particulate and can quickly become overloaded. As the filter fills up, it will no longer be able to clear the air efficiently, and particulate will find a way through and into your home. Because of this, it is important to replace the filter the more it is used.

WHEN SHOULD I REPLACE MY HEPA FILTER?

For regular home use, most HEPA filters can be replaced once a year. However, during wildfire smoke season, filters may need to be replaced more than once to achieve maximum efficiency of the filtration system. We recommend replacing your filter just prior to wildfire smoke season so you are equipped with a clean filter, and monitoring it for build-up throughout the smoky weeks.

You can check the filter to see how much material has accumulated (the darker, the dirtier!) Also check the manufacturer recommendations for your filter. Some filters even come with a sensor that indicates when filter replacement is necessary. We recommend keeping at least one backup filter on hand during smoke season. 

WHERE SHOULD I PURCHASE A NEW HEPA FILTER?

Replacement filters may be purchased directly from the manufacturer of your HEPA PAC. You can also find them online or in person at a retailer. Purchasing an off-brand filter is usually the most economical way to go: just make sure the off-brand replacement filter is compatible with your HEPA PAC system! This isn't hard to do: often there compatibility information noted on the replacement filter you are purchasing.
Watch Reeve show you how to change the filter in your HEPA air purifier!