How to use face masks to avoid transmission

The coronavirus pandemic has caused a critical shortage of face masks for health care professionals.

Now scientists and public health officials are working to get the word out on the proper use of masks in the fight against the spread of COVID-19: Who needs them, when and why?

Here’s a quick look at what you need to know about face masks and coronavirus:

Q: Should I wear a mask?

A: With medical supplies running critically low, the World Health Organization and Centers for Disease Control and Prevention had not recommended that people who are healthy wear face masks, unless it is specifically recommended by a health care professional. The CDC has urged that only people who have COVID-19 and are showing symptoms should wear masks, to protect others from the risk of infection.

However, on April 1, the CDC said they are reviewing their guidelines and may relax that stance.

Some governments aren’t waiting for the updated recommendations. In Riverside County, health officials may be the first in California to plainly urge people to cover their noses and mouths when they leave home for the doctor, the grocer or the pharmacy.

Also on April 1, the California Department of Public Health issued guidelines that said wearing “face coverings,” including scarves and bandannas, could help prevent the spread of the coronavirus. The state discouraged the use of N95 respirators or surgical masks, which are in short supply and needed by health care workers and first responders, by most people. Health officials also cautioned against relying solely on such coverings and said people should continue frequent handwashing and maintaining physical distance from others.

Some experts have disputed past advice to ignore masks, pointing to the widespread use of masks in the Asian countries that have most successfully curbed the spread of the virus.

George Gao, director-general of the Chinese Center for Disease Control and Prevention, told Science magazine, “The big mistake in the U.S. and Europe, in my opinion, is that people aren’t wearing masks.”

Q: What purpose do face masks serve?

A: The coronavirus is most commonly transmitted through respiratory droplets, such as when someone sneezes or coughs. A study done by the National Institutes of Health indicates that the virus that causes COVID-19 can remain suspended in the air for up to three hours.

“This virus is transmitted by droplets and close contact,” Gao said. “Droplets play a very important role — you’ve got to wear a mask, because when you speak, there are always droplets coming out of your mouth. Many people have asymptomatic or presymptomatic infections. If they are wearing face masks, it can prevent droplets that carry the virus from escaping and infecting others.”

In a health care setting, flat surgical masks are designed to protect against large droplets, splashes or sprays of bodily or other hazardous fluids, according to the CDC. These do not form a seal around the face but do create a physical barrier between the mouth and nose of the wearer and potential contaminants in the immediate environment. Wearing masks also protects patients from the wearer’s respiratory emissions.

More advanced N95 respirators reduce the wearer’s exposure to particles including small-particle aerosols and large droplets, filtering out at least 95% of airborne particles. The edges of the respirator are designed to form a seal around the nose and mouth, according to the FDA.

Wearing a mask may prevent the spread of infected droplets by asymptomatic individuals and also reduce the likelihood that people will touch their faces.

Q: What is the proper way to wear masks?

A: The WHO guidelines for effectively wearing a face mask are as follows:

Before putting on a mask, clean hands with alcohol-based hand sanitizer or soap and water.

Cover your mouth and nose with the mask and make sure there are no gaps between your face and the mask.

Avoid touching the mask while using it. If you do, clean your hands immediately.

Replace the mask with a new one as soon as it is damp and do not reuse or share masks.

To remove the mask, take it off from behind (do not touch the front of mask), discard immediately in a closed bin, and wash or sanitize your hands.

Q: Why is there a shortage of masks?

A: The panic that caused people to stockpile toilet paper and hand sanitizer as the pandemic spread also led to a global run on sales of face masks.

As a result, medical centers are facing severe shortages that are being attributed not just to high demand, but to disruptions in supply.

Most of the world’s surgical masks are made in China, where, according to the Associated Press, the coronavirus outbreak has caused shortages of workers, and manufacturers say they are struggling to get enough raw materials to make the masks.

Q: Can I make my own mask?

A: The CDC updated its guidelines and is allowing health care workers to use bandannas, scarves or “homemade masks” to cover their faces “as a last resort” while treating COVID-19 patients.

Fabric face masks are not as effective as N95 masks, according to the FDA.

The FreeSewing Open Source Project is providing free face mask sewing patterns for download. There are also tutorials on YouTube for making homemade face masks, including one by fashion designer Amanda Perna, who also provides a PDF template.

Q: Is it safe to reuse a mask?

A: There are a number of risks associated with extended use and reuse of face masks. But due to the critical shortage, both the CDC and FDA have made allowances for cleaning for reusing N95 masks.

Extended use, the practice of wearing the same N95 respirator for repeated close-contact encounters with several patients without removing the respirator between encounters, is preferred to reuse because it involves less touching.

If a respirator is being reused, the CDC recommends the wearer consider use of a cleanable face shield over the N95 to reduce surface contamination. It also suggests sanitizing your hands before and after touching or adjusting the respirator.

Respirators should be discarded if damaged, used during aerosol-generating procedures, or if contaminated by blood, nasal discharge or other bodily fluids.

The FDA has approved using aerosolized hydrogen peroxide to decontaminate masks without causing the material to deteriorate. The system allows respirators to be used up to 20 times, with a 2.5-hour decontamination process between each use.

Surgical masks are single-use only, as they present a risk of auto-contamination.

Cloth masks should be washed between each use, in hot water with regular detergent, and dried completely on a high heat setting. Always sanitize your hands after handling and do not touch your face.

Q: Can I donate my masks?

A: Yes, if they are the professionalgrade kind sold in stores.

Almost all hospitals say they want only unused, unopened masks whose protection level is understood and guaranteed.

While well intentioned, donations of hand-sewn masks will generally be turned away. Call ahead before you bring donations of hand-sewn masks to a hospital, and be prepared to hear that they will not accept them.

A detailed FAQ is available on SFChronicle.com about where to donate masks and other medical supplies.

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