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VTT: Masks protect others, but not user

The study by Finland's Technical Research Centre suggests masks slow progress of virus, but cannot eliminate its spread.

Hengityssuojain ja kädet.
File photo of face mask. Image: Helen Sessions / Alamy

A research study into the effectiveness of masks by the Technical Research Centre of Finland (VTT) has concluded that a fabric mask does not protect the wearer from coronavirus, but can help to protect other people.

Researchers also found that the wearer of a fabric mask is several times more likely to contract the virus compared with a person wearing professional protective equipment.

Although the daily wearing of masks will not eliminate the possibility of becoming infected, they can help to reduce the overall number of infections, according to VTT's research professor Ali Harlin.

"Masks can be an additional aid in the attempts to open up society again, but they alone are not the answer," Harlin said. "In addition, good hand hygiene, general caution and an understanding of how to use masks are also required."

According to Harlin, people can continue to protect themselves by keeping a suitable distance from others, but in busy or cramped public spaces such as waiting rooms, public transport or shopping queues, masks can be important in containing the spread of the virus.

"It definitely helps that we do not unknowingly infect each other. When we talk, we eject droplets, and when we cough, we eject a lot of droplets," Harlin explained. "The virus travels on these droplets but the mask can stop or slow their progress."

Polyester better than cotton

VTT's study also tested polyester and cotton masks to determine which material was better at filtering viral particles, and concluded that polyester is a better option than cotton due to its water-resistance.

Based on the results of VTT’s study, the ability of a cotton mask to filter particles is around 20-30 percent while a polyester mask’s filtration rate is about 40-50 percent.

Story continues after photo.

tutkimusprofessori Ali Harlin, VTT
VTT Research Professor Ali Harlin. Image: VTT

"It would be better to use polyester instead of cotton for two reasons: cotton gets wet and it would seem that cotton fabric would not have as good filtration values as polyester fabrics," Harlin explained, but warned that people should make individual choices about the type of mask they wear.

"It is also important to choose a mask which does not suppress or interfere with breathing," Harlin said. "There are people who should not wear a mask at all and they must therefore put other precautions in place."

Ministry of Health compiling data

The Ministry of Social Affairs and Health (STM) is compiling research data on the use of face masks by the Finnish population and also internationally. So far, the Finnish government and authorities have been cautious about recommending that people in Finland use masks.

The government has commissioned an external study, which looks at both the scientific research literature regarding the criteria for recommendations and guidelines made by other countries. The study is ongoing and is scheduled for completion before the end of May, with government guidelines on the wearing of masks expected by early June.

An Yle-commissioned opinion survey found that just under half the respondents said they did not want face mask usage in Finland to become obligatory.

According to Harlin, clear guidance from the government on this issue is very difficult because the guidelines are useful only if people know and want to follow the instructions.

A strong recommendation could, in Harlin’s opinion, work better than an absolute order.

"For example, in the case of SARS, it became clear that people would not wear masks if they didn’t find it meaningful. It is also difficult to create unambiguous and simple guidelines, which are reliable too," Harlin noted.

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