Masks can prevent Covid-19, and there ways to make them more effective; claim that they trap excess carbon dioxide is false

Photo by Kemal Yildirim, Getty Images

Wearing a face mask can help prevent the spread of Covid-19, ad certain mask combinations and modifications can increase a mask's effectiveness.

A study led by researchers from the National Institute for Occupational Safety and Health looked at how efficiently different mask types, combinations, and modifications blocked respiratory aerosols like those that carry the coronavirus. The study involved humans and simulator mannequins in various experiments to simulate coughs and exhalations to see how well aerosols were blocked.

The study found that layering a three-ply cloth mask over a medical mask (double masking) or securing a medical mask with an elastic brace provided the best protection. Using earloop toggles or an earloop strap, or knotting and tucking the mask, also increased performance as compared to medical masks without modification. Two other modifications, crossing the earloops or placing a bracket under the mask, did not increase performance. The study is published in the peer-reviewed American Journal of Infection Control.

“Since the start of the Covid-19 pandemic, there has been considerable confusion about the most effective use of face masks, especially among the general public, to reduce the spread of infection,” said Ann Marie Pettis, president of the Association for Professionals in Infection Control and Epidemiology. “The NIOSH study findings are important and timely because they identify specific, practical combinations of face masks and mask modifications that may improve mask seal and thereby measurably reduce the expulsion of infectious aerosols into the environment.”

A claim that masks trap dangerous levels of carbon dioxide is false, medical experts say. "Wearing a mask does not raise the carbon dioxide (CO2) level in the air you breathe," says the Centers for Disease Control and Prevention. "A cloth mask does not provide an airtight fit across the face. The CO2 completely escapes into the air through the cloth mask when you breathe out or talk. CO2 molecules are small enough to easily pass through any cloth mask material. In contrast, the respiratory droplets that carry the virus that causes Covid-19 are much larger than CO2, so they cannot pass as easily through a properly designed and properly worn cloth mask."