Study: Surgical face masks protect against aerosols, plastic face shields provide no protection

Editor's Note

Wearing a surgical face mask can provide similar protection against aerosols as wearing a respirator, but face shields provide little or no protection, finds this study, which will be presented at the European Congress of Clinical Microbiology & Infectious Diseases July 9-12.

German researchers compared 32 types of masks, including cloth and surgical masks, respirators, and face shields.

The first experiment, which measured the filtration efficacy of mask material, found that filtration efficacy was lowest for cloth masks (28%), followed by non-certified surgical masks (63%), and certified surgical masks (70%). KN95 respirators filtered out 94% of particles and FFP2 respirators 98%.

The second experiment measured air pressure on either side of the mask and found that surgical face masks produced the lowest drop in pressure and would provide the least resistance to breathing. Respirators produced pressure drops that were 2-3 times higher.

The third experiment measured the filtration efficacy of masks as worn. Cloth and non-certified surgical masks had the worst as-worn filtration efficacies, filtering out just 11.3% and 14.2% of particles, respectively. Certified surgical masks had similar filtration results (47%) as KN95 respirators (41%) and FFP2 respirators (65%).

Face shields had no significant effect.

The researchers concluded that members of the public should wear certified surgical face masks rather than cloth masks or face shields, which performed poorly, or respirators, which should be reserved for healthcare workers. They also advised that because surgical face masks produce less resistance to breathing and are more comfortable to wear, they might lead to better adherence and protection of healthcare workers than respirators, which are 2-3 times harder to breathe through.