Bulgarian Scientist: Masks with Filter Protect only Those Who Wear Them

The masks with a valve and a filter protect only those who wear them, but not the people around them " said Prof. Penka Petrova, director of the Institute of Microbiology at the Bulgarian Academy of Sciences.

This comes after a study of safety masks was conducted in Bulgaria. According to the new order of the Minister of Health from February 1 to April 30, it will no longer be allowed to cover the mouth and nose with a scarf or helmet instead of a mask.

It is permissible to wear cheaper disposable masks, as well as textile, and not necessarily more expensive and higher class FFP2, to which a number of European countries have switched. Prof. Penka Petrova reminded that the masks type FFP2 have a very high degree of protection.

"They are four-layered, they stop 95% of the aerosols, and the air that we inhale and exhale is completely sterile," she explained. She herself believes that textile masks are not as effective in limiting the spread of the virus, and reminded that over time, the threads in the fabric may become looser and this may increase permeability. "The tests we did showed that after 15 washes at 40 degrees, the effectiveness of textile masks decreased a lot," she said.