The Centers for Disease Control and Prevention (CDC) made headlines on Dec. 2 when they announced a major COVID guideline change that cut the length of recommended quarantine time from 14 to just 7 days in some cases. But the CDC wasn't the only major health agency to amend its coronavirus-related guidelines this week. The World Health Organization (WHO) also took the time to update its face mask recommendations, tightening the rules on when and where they should be worn. But the WHO also was clear to specify that one type of face covering won't do enough to protect you: a face shield. Read on to find out about the changes, and for more on which mask to avoid, check out If Your Face Mask Has One of These, Stop Using It Immediately.In the update that was published on Dec. 1, the WHO carefully outlined that the use of face masks is superior to the use of face shields because the latter won't block the wearer's exhaled droplets and can't stop them from inhaling droplets either.Outside of being used in combination with a mask, the WHO did outline a specific situation in which they could be considered. "In the context of COVID-19, some children may not be able to wear a mask due to disabilities or specific situations such as speech classes where the teacher needs to see their mouths," the guidelines read. "In these cases, face shields may be considered an alternative to masks, but they do not provide the equivalent protection in keeping the virus from being transmitted to others."The updated recommendations also state that any face shield being used "should cover the entire face, wrap around the sides of the face, and extend to below the chin. Caution should be taken while wearing one to avoid injuries that could break it and harm the eyes or face."The CDC has also stated that face shields are not an acceptable replacement for face masks. "Face shields have large gaps below and alongside the face, where your respiratory droplets may escape and reach others around you," the agency's guidelines warn. "At this time, we do not know how much protection a face shield provides to people around you."Of course, finding the right face mask is complicated, too. Read on to find out if your mask is up to snuff, and for more on why wearing face masks could be important in the coming weeks, find out How Likely You Are to Catch COVID in the Next Month, Expert Says.Read the original article on Best Life. 1 It needs three layers.Scientists at Virginia Tech University recently tested 11 different types of face masks, including nine cloth masks made from materials such as coffee filters, a cotton T-shirt, and other fabrics as well as a face shield and surgical mask, Yahoo! News reports.The results pointed to a clear winner. "We recommend now based on this study that people use a three-layer mask," said Linsey Marr, PhD, a leading aerosol scientist at Virginia Tech and co-author of the study, during a press conference on Nov. 23. Specifically, Marr recommends a mask in which "the outer two layers are a tightly woven but flexible material that allows the mask to conform to your face," with a layer made of vacuum bag or filtration material in the middle. And for more on the latest COVID news, check out These 2 Places Could Be Closing Soon, White House Official Warns. 2 It shouldn't have a ventilator.Having a breathing vent on your mask may make you feel more comfortable, but health agencies roundly agree that they're completely ineffective at stopping the spread of COVID-19. According to a visualization study conducted by research engineers at the National Institute of Standards and Technology (NIST), while medical-grade N95 masks completely stop the passage of droplets, N95 masks with a ventilator valve do almost nothing to stop the spread. In fact, droplets moved almost as far and as quickly with a mask with a ventilator as they did in cases without any kind of face covering at all."When you compare the videos side by side, the difference is striking," Matthew Staymates, the NIST research engineer who created the visualization, said in a statement. "These videos show how the valves allow air to leave the mask without filtering it, which defeats the purpose of the mask." And for more on when PPE will be a thing of the past, check out This Is Exactly When Dr. Fauci Says We Can "Throw Our Masks Away". 3 You need to wash it regularly.A recent meta-analysis published in the journal BMJ Open analyzed data from a 2015 study on the effectiveness of cloth face coverings against the seasonal flu, cold viruses known as rhinoviruses, and genetically similar coronaviruses. The researchers found that not cleaning your mask daily created a high risk for contracting coronavirus."Both cloth masks and surgical masks should be considered 'contaminated' after use," Raina MacIntyre, PhD, who conducted the study, said in a statement. "Unlike surgical masks, which are disposed of after use, cloth masks are re-used. While it can be tempting to use the same mask for multiple days in a row, or to give it a quick hand-wash or wipe-over, our research suggests that this increases the risk of contamination." And for more mask mistakes to avoid, check out This Is the One Thing That Is Making Your Mask Useless, Scientists Say. 4 You have to wear it right.Just because you have a mask on your face doesn't mean it's doing its job. Wearing it below your nose, pulling it under your chin to speak, or wearing a loose-fitting mask practically negate the benefits of wearing one at all.According to an online mathematical model of COVID transmission developed by a pair of scientists from the Massachusetts Institute of Technology (MIT), wearing a surgical grade mask in a 20-foot-by-20-foot room with 10 people made it safe enough to spend two hours together without risk of exposure to the virus. But factoring in that people in the room could be pulling their masks below their nose or wearing one that doesn't fit properly, the amount of safe time dropped down to just 32 minutes. And for more on this, check out It Only Takes This Long to Get COVID in a Room With Someone Who Has It.