Maryland Today | N95 masks are nearly perfect at blocking COVID, UMD…

A study led by the University of Maryland and published Wednesday found that while all common masks offer significant protection against the virus that causes COVID-19, N95 masks are the most effective at reducing the amount of virus shed by an infected person.

So-called “duckbill” N95 masks received the highest scores in a study that measured the breath of subjects tested both with and without a mask to compare SARS-CoV-2 emissions. The inexpensive masks, which have two head straps and horizontal seams, captured 98% of the exhaled virus. Electronic Biomedicine.

The researchers also found, in what may be a surprise to many, that cloth masks performed better than certain brands of KN95 masks they tested. Surgical masks performed the least well of the four, but still tested to block 70% of the virus. (To reflect mask use in the general population, study volunteers were not fit-tested for the masks or trained on how to wear them properly.)

“The main message is that the study shows that any mask is much better than no mask, and that the N95 is much better than other options,” said Donald Milton, the study's lead author, a professor of environmental health and a world expert on airborne viruses.

The researchers also said their findings suggest that N95 masks, also known as respiratory protective masks, should become the standard of care in nursing homes and health care settings when respiratory viral infections are widespread and the risk of infection is elevated.

School of Public Health Public Health Aerobiology Laboratory (PHAB Laboratory) The effort began in May 2020, shortly after the outbreak of the COVID-19 pandemic, and focuses on masks not as a means of protection from airborne viral particles around us, but as a tool to control the spread of the virus from its source – an infected person.

The researchers asked volunteers with COVID-19 to breathe into a device called the Gesundheit II machine, which Milton and his colleagues developed to measure the virus in exhaled breath. Participants blew into the machine for 30 minutes at a time while repeating the alphabet, singing “Happy Birthday,” and yelling “Go Terps!” repeatedly, first wearing masks and then without.

“Our data suggest that COVID-19 patients with mild symptoms exhale just over twice as much infectious material per hour when not wearing a mask,” said lead author Jianyu Lai, a postdoctoral researcher in the PHAB lab. “But when they wear an N95 mask, the risk drops exponentially.”

The study includes co-authors from UMD's A. James Clark School of Engineering and the World Health Organization Collaborating Centre for Infectious Disease Epidemiology and Control at the University of Hong Kong.

According to Milton, the duckbill N95 blocked 99% of large virus particles and 98% of small virus particles thanks to its tightly sealed design, powerful filter, and large air space for breathing circulation. Perhaps surprisingly, the widely used KN95 mask (sometimes touted as nearly as effective as the N95) was no better than a variety of cloth masks or surgical masks. Milton believes that the generic brand of KN95 masks tested do not fit the face well, making them more susceptible to air leakage than the duckbill and other masks studied. That deficiency is exacerbated by the powerful filter, which has a high resistance to flow, pushing air (and virus particles) out the sides of the mask instead of through the filter.

Cloth masks also performed better than both KN95 and surgical masks. Milton speculates that cloth masks were the second most effective of the masks they tested because they provide more coverage around the face and create a tighter seal than either KN95 or surgical masks. They also offer less resistance to airflow, allowing air to pass through without bypassing the filter.

Limiting the amount of viral particles in the air is a key way to control highly contagious respiratory viruses in general, Milton said. This is especially true for COVID-19, especially the Omicron variant, which breaks through the immunity people have acquired through vaccination or previous infection. Milton and Lai hope that their findings will inform future health policies, including when fighting potential epidemics such as avian flu and common influenza.

“Our study clearly shows why non-pharmaceutical responses like mask wearing are so important and why studies like this are needed to determine which masks are most effective,” Milton said.