Not all N95 masks are effective in defending against the coronavirus.
Face masks with exhalation valves, instead of blocking particles that could spread COVID-19, actually allow the wearer’s germs to spread, according to health experts. Their ability to release large respiratory droplets in the air has some worried, including San Francisco health officer Dr. Tomás Aragón, who even signed an order in May warning of the potential dangers of these particular masks.
“Any mask that incorporates a one-way valve (typically a raised plastic cylinder about the size of a quarter on the front or side of the mask) that is designed to facilitate easy exhaling allows droplets to be released from the mask, putting others nearby at risk,” the order reads.
Centers for Disease Control and Prevention (CDC) guidance states that standard N95 respirators reduce the wearer’s exposure by filtering out around 95 percent of air particles, while those with exhalation valves allow “unfiltered exhaled air to escape into the sterile field.”
Dr. Matthew L. Springer, a cardiologist at the University of California, San Francisco, told the San Francisco Chronicle that masks with these values are “practically useless.”
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“Given that most of the value of these masks is not to protect the wearer but to protect others from a potentially contagious asymptomatic wearer, those one-way valves make the masks practically useless for protecting others,” he said. “So all those potentially contagious people are spewing unfettered large respiratory droplets, probably even in a concentrated stream going through the valves.”
If you have a mask with an exhalation valve, health experts say you can cover it with a piece of tape.
