An air purifier removes airborne particulate matter and some gases from your home. Air filtration is important because exposure to air pollution can irritate your respiratory system, trigger asthma symptoms, and increase the need for allergy medication. Studies also show that cognitive effects such as trouble concentrating can occur at levels of air pollution common in indoor environments.

Mechanical filters (including HEPA) use fans to force air through a dense web of fine fibers that trap particles. They’re effective at capturing microscopic dust, pollen, and mold spores (though some models that don’t meet the official HEPA standard are labeled "HEPA-type" and still performed well in our tests). Mechanical filters don’t help with gases or odors.

Activated carbon filters capture certain types of chemical gasses through a process called adsorption. Some, like those used in Molekule, use a light-activated catalyst that reacts with odor-causing molecules to break them down at the molecular level. Activated carbon filters get saturated more quickly than mechanical filters, though, so you’ll need to replace them every three months or so, instead of every six to 12 months as you would with a mechanical filter.

If you’re looking for an air purifier to help alleviate allergies, look for a model with a high MERV rating that has a large enough filter for the room size you’ll be using it in. You’ll also want to check out the motor quality and its CADR ratings, which measure how much filtered air moves through the filter at a given speed.   air purifier