When you’re bored at home and cleaning just about everything in sight—bleaching countertops and doorknobs, your carpets, and even your computer and phone—you might start to wonder: Is there a way to clean the air in my home? That’s where air purifiers come in. Most air purifiers remove particulates—dust, pollen, mold, smoke, and pet dander, for example—and some can also kill bacteria, says Dr. Cara Pensabene, medical director of EHE Health.

But do air purifiers really work? Yes—provided you pick the right one, says Pensabene. “Not all are created equal, and one which is designed to remove dust may not work so well against pathogens.”

Before shopping for air purifiers, first identify your needs. For those with allergies or asthma, look for high efficiency particulate air (HEPA) filters to control the environment and the allergens in it, she explains. These air purifiers use fine glass threads tangled together to form a filtering mat that collect particles down to 0.3 microns in diameter. For even more filtering power, there are also electrostatic precipitators which remove particulate down to 0.1 microns in diameter, says Pensabene. If your goal is to rid your home of pathogens, be sure to look for one specifically designed to kill bacteria—filters with photo electrochemical oxidation, or PECO, technology. Even though most filters will catch germs, they can then thrive in the filter’s environment and increase their populations if not specifically designed to eradicate the bacteria, says Pensabene.

It’s also worth considering ease of use, energy efficiency, noise level, and maintenance costs, as these factors can all play a role in how you use the machine, and thus, how effective it is.