Confused about whether you actually need to wear a mask during the new coronavirus pandemic? We’re not surprised—there’s been a lot of conflicting advice. For months the word from the Centers for Disease Control and Prevention (CDC) was that you only needed a mask if you were a health care worker, otherwise taking care of someone who was sick, or sick yourself. But then cities like Los Angeles started to recommend that people wear nonmedical face masks when out and about. The CDC cleared the air last week when it officially recommended that everyone use homemade cloth face coverings in public places where social distancing is hard to maintain, like grocery stores and pharmacies.

Homemade is the key word here. Many U.S. communities are now facing a critical influx of COVID-19 patients and equipment shortages; some hospital workers have reportedly resorted to using plastic garbage bags and eye “shields” made from water bottles. Unless you’re a health care worker treating people with COVID-19 or some other type of medical first responder, you really shouldn’t be trying to find surgical or N95 masks. N95 face masks are tight-fitting and have a filter that blocks at least 95% of large and small airborne particles. Surgical masks are looser-fitting (pathogens can sneak in around the edge) and don’t offer reliable protection from inhaling smaller airborne particles, but they have been FDA-approved to protect against large droplets, splashes, and sprays of bodily fluids. When a pandemic reaches this level of crisis mode, the CDC says it’s essential to reserve these modes of protection for people on the front lines treating patients. Based on what experts know so far, it seems that “the more virus you’re exposed to at any given time, the more likely you are to get sick,” Eleanor J. Murray, Sc.D., assistant professor of epidemiology at Boston University School of Public Health, tells SELF.

While the CDC continues to stress that we all need to keep washing our hands frequently and maintaining a distance of at least six feet from people not in our household (when possible), the group says wearing a mask may offer some protection when you do have to go outside. But how much, exactly? And what’s the best way to wear a homemade face mask for maximum protection? Here’s everything you need to know.

Can a face mask really help you avoid the new coronavirus?

Experts initially hesitated to recommend masks for everyone because they believed that the new coronavirus could only be spread by sick people with symptoms. “In that situation, it’s really easy to say to wear a mask if you have symptoms,” says Murray.

Data from the CDC has now shown that people can transmit the virus at least a couple of days before they experience symptoms. What’s more, various estimates suggest that anywhere from 25 to 50% of all people who have COVID-19 may not have symptoms at any point in their illness. (These figures are inconclusive.) That means we could accidentally infect others even if we don’t think we’re sick. Masks reduce that risk. “If everyone has one on, everyone is protecting each other,” Marybeth Sexton, M.D., assistant professor of infectious diseases at Emory University School of Medicine, tells SELF.

The general consensus is that homemade masks mainly help keep a sick person from spreading germs, explains Marc Lipsitch, D.Phil., professor of epidemiology at Harvard University T.H. Chan School of Public Health, pointing to flu studies that have shown as much. There isn’t strong scientific evidence that homemade masks filter out enough particles to protect the people wearing them. Still, by preventing someone who is sick (even without symptoms) from expelling as much of the virus into the air, homemade masks may help lower new coronavirus infection rates overall. A small 2013 study in Disaster Medicine and Public Health Preparedness concluded that while surgical masks were three times more effective than cloth masks at blocking particles, homemade versions still significantly reduced how many microorganisms a person was putting into the air and were better than nothing in an emergency situation.