Ask Wirecutter: Do I Really Need a Portable Air Purifier?

HVAC (heating, ventilation, and air conditioning) does a very good job of filtering the air if the return registers or air handler have decent MERV-rated filters installed. MERV stands for Minimum Efficiency Reporting Values, and it indicates how well your filter can capture particles between 0.3 and 10 microns.

You should get a filter with a MERV rating of 11 or higher to most efficiently capture pollen, dust, smoke particles, and airborne germs.

You may have a system that uses UV-C light to deactivate grimies like viruses, bacteria, and mold so they are no longer infectious. But UV doesn’t capture them like a filter does (and bacteria and viruses captured by filters do not reenter the air the way they do with UV-C). UV may also help with some odors, which particulate filters do nothing about.

It’s really the air circulation through the filters that matters most, so you want to ensure that your HVAC system runs for several hours every day (whether it’s cooling, heating, or just moving air around). That way all the air in your home will pass through the filters several times, compounding their effectiveness.

A portable air purifier makes a big difference during moments of increased air pollution, like if something burns in the kitchen, a wildfire is nearby, or it’s a heavy pollen season. Running a unit like your Coway Mighty on high for a few minutes cleans a room much faster than HVAC and then keeps it squeaky clean running on medium or auto.

“I keep a Coway air purifier at my dad’s for this reason,” says Tim. “It’s tucked in a closet most of the time, and we let the HVAC keep the air clean. But whenever we use the fireplace, we pull out the Coway to help clear the air of the smoke that is entering the living space and could aggravate my niece’s asthma. It makes a world of difference.”

All of Wirecutter’s thoroughly vetted air purifier picks perform well as long as you’re cleaning the prefilter monthly and changing out the HEPA filter regularly (usually every eight to 12 months—check the operator’s manual).

But as you’ve already learned, we do love the Coway Mighty the most for its durability, compact size, and efficiency.

Unfortunately acute weather events (which are becoming more common), such as wildfires from Canada to California, can smoke up the skies hundreds of miles away. A bit of emergency prep in the form of an air purifier would have a big impact on your health and well-being.

You can DIY an air purifier from a box fan and filters during an extreme event when you cannot open a window to bring in fresh air, but Tim says having a purpose-built unit is better for a number of reasons.

“These DIY units are big, ugly, and they don’t save you money long-term. They require a box fan, plus one to five MERV filters that cost about $10 apiece and only have a two-month lifespan. They’re a good option in an emergency situation, but it’s far better to think ahead and buy an air purifier before you need it,” he says.

Whether you do or don’t have an HVAC system with filtration, you can certainly own one air purifier and move it from room to room as you need it. Our main picks are rated to cover about 350 square feet, but Tim has witnessed them handle spaces twice that size.

While we sing the praises of both air purifiers and efficient HVAC, neither helps with cigarette odors. That’s because they aren’t particularly good at capturing the volatile organic compounds (VOCs) that our noses interpret as smells.

Air purifiers physically trap particulate matter, and while some have a token odor-capturing VOC filter with activated carbon, they just don’t have enough carbon for it to really make a difference. And once the carbon reacts with VOCs and has done its job, it’s spent.

Your only true answer for cigarettes and non-airborne mold is professional remediation (air purifiers do capture airborne mold, but you need to address the root issue to actually solve the problem).

In the case of CO² and gas stove exhaust (or if you’re using something like an oven cleaner, which we don’t recommend), open a window to get fresh air in and stinky air out.

I hope this was enough to convince your spouse of the value of your air purifier. It’s worth making a little room in the moving truck for the Coway Mighty to come with you.

This article was edited by Jason Chen.