Photo: Washington Post Photo by Carolyn Van Houten
These face masks, which you see with coin-sized valves on the front, may look fascinating, but they cannot prevent the spread of the novel corona virus as well as the apparently non-ventilated masks with lower technology.
Some masks for hot, dusty construction work, where dust is to be filtered out before it hits the wearer’s lungs, have “exhaust” valves that allow exhaled air to drain more easily to keep the wearer cooler.
The company 3M, which manufactures valve masks for such professions, shows on their website how they work: Inhaled air is filtered through the fabric part of the mask, and hot, moist exhaled air exits through the valve. The system may be exactly what you want when you pull out a kitchen for remodeling, but the valve negates the purpose if you try to slow the spread of a virus.
Public health experts have recommended wearing a mask to prevent breath droplets from spreading into the air when you exhale, speak, cough, or sneeze, and the valves let these droplets pass.
You will find that medical masks have no valves.
In its guidelines for wearing masks, San Francisco states that masks with valves do not meet the standards.
“Any mask that contains a one-way valve (usually a quarter-inch raised plastic cylinder on the front or side of the mask) that makes it easy to exhale allows droplets to be drained from the mask, bringing others nearby at risk, “says the order.
The disease control and prevention centers recommend simple cloth masks to the public to prevent the spread of Covid-19. A few layers of cotton prevent most of the potentially infectious breath droplets from escaping into the air around you, and they’re also much cooler than the form-fitting N95 masks.