Wearing a mouth and nose cover is one of the most important corona measures to reduce infection. However, using the mask for longer periods makes it moist. A study shows how moist masks protect even more effectively.
For more than a year, masks have been mandatory in many areas of our lives in order to stop the spread of the coronavirus and reduce the number of infections. Everyone knows hot to wear a surgical or FFP2. While the effectiveness of various dry masks has been researched, there is a lack of extensive research into wet masks. However, people wear the masks for a long period of time and during that time the mask is blocked by respiratory droplets released when breathing, coughing, sneezing, etc. Now a team of researchers from the USA has found out how the protection of the masks can be increased.
New study: Moist masks have a positive effect
They first looked at how well moist masks hold back droplets. It was then determined what happens to the droplets when they come into contact with wet masks. To do this, the researchers used a syringe pump to create dummy breath drops on a mouth and nose mask and recorded with a high-speed camera what happened when the droplets hit it. This process was repeated until the mask was damp.
▶ The result: the filter effect of mouth and nose protection improved when it was wet.
That sounds amazing at first. They always say that the masks must never get wet. But as the researchers explain in “Physical Reviews Fluids“, wet masks make it harder for the droplets to penetrate and escape.
▶ Specifically, this means: the more moisture there is in the tissue of a mask, the faster a droplet that is created when coughing or sneezing has to move in order for an aerosol produced from it to penetrate the mask.
Important: Masks should not be completely moistened
However, the research team suggests that everyone should follow the general recommendations and change their mask when it’s wet. Because with moistened masks at some point the protective effect against droplets and aerosols diminishes.
The study found that droplets from a cough or sneeze have to be traveling at a higher velocity to be pushed through a mask when wet, compared to when it’s dry. On hydrophobic masks with low absorptivity,like surgical masks, the respiratory droplets form small beads on the mask’s surface, providing additional resistance for the impacted droplets against possible penetration.
In addition, damp masks make it harder to breathe. The inhaled air is filtered less efficiently and could thus escape at the edge of the mask more easily than with dry masks.
Surgical masks are generally single-use items. However, they can also be used several times if they are worn for a very short time. Then they should be disposed of in the residual waste. FFP2 masks can be reused if handled correctly.
A word of caution
This study only investigated the effects of wet masks on droplet penetration; the researchers note that people should follow public health guidance to change their mask if it is wet, since wet masks are harder to breathe through, less efficient at filtering inhaled air, and can vent more around the edge of the mask than dry masks.