Homemade masks can increase the risk of Covid 19

Meyken Houppermans
Founder and Head Coach
Starting December 1st wearing a face mask in public space is mandatory in The Netherlands. At CrossFit Eudokia we wear a face mask before,during and after our workouts. Our members can choose between their own facemask or our custom-made double layer cotton ones. Does it matter what type of mask you wear?

In our previous article we discussed the positive effects of wearing a face mask on your training results in the long run. We also mentioned that scientific research on the effects of face masks on the reduction of the spreading of Covid 19 are somewhat inconclusive due to several factors among which methodological ones. Nevertheless, the common thread seems to be that wearing a face mask can provide some benefits in relation to Covid 19.

In this article we discuss a study (Asadi et al, 2020) about he efficacy of face coverings in controlling outward aerosol particle emission from expiratory activities. This study provides interesting insights into the effect of different types of face masks during different types of activities.This might give us some clues or indications on how to create and optimize a safe training environment, although the research results cannot be translated and implemented one- on- one of course.

The study in short

In this study, seven types of face masks were tested in four types of expiratory activities: Breathing out through the mouth; talking; coughing; and chewing. Of those seven types of face masks three were medical ones and four were homemade. The homemade masks were: a single-layer paper towel mask; single-layer cotton t-shirt mask; a double-layer cotton t-shirt mask; and a double-layer cotton t-shirt mask that wash hand washed before testing. None of the masks were fit- tested and the individuals testing the face masks were not trained in how to put the mask on.

The results in short

In the activities of breathing, talking and coughing, the medical face mask reduced aerosol partical emission significantly, up to 74 to 90%, compared to not wearing a mask. In the activity of chewing, the medical masks had no statistically significant effect on particle emission compared to no mask.

In the activity of breathing and talking, the homemade single layer paper towel mask also had a significant effect in decreasing outward emission rate. In the activity of coughing, this paper mask yielded no statistically significant difference compared to no mask.

Pretty shocking is the fact that wearing a single layer t-shirt mask while breathing and talking yielded a significant increase in aerosol particle emission rates compared to no mask, at some point up to 384%. Wearing a double-layer cotton t-shirt mask had no statistically significant effect in these activities.

In coughing, the homemade single and the double layer t-shirt masks yielded a significant increase in outward particle emission compared to no mask. In the activity of chewing, all homemade masks substantially increased the particle emission rate.

Furthermore, the double-layer cotton masks reduced the emission of larger particles indicating some reasonable efficacy towards reduction of the expiratory particle emission. Last, washing the homemade maskshad no effect: the results were the same for the unwashed and the washed homemademasks.

How can this be explained?

One probable explanation for the increase of particle emission in the homemade masks has to do with the friction of the material when the mask is put on and, in this study, when chewing while wearing the mask. Putting on a face mask and chewing both create material friction and that can generate aerosol particle emission. This might explain to some point the measured increase in particle emission in the homemade masks during expiratory activities. One explanation that could be ruled out was the fact that people speak louder with a mask on, which would result in a greater output of particles. These conditions were similar for all types of masks and therefore, this mechanism alone cannot explain the increased particle output in the handmade masks.

Now what with our homemade masks?

The study shows that medical masks are the most effective in decreasing aerosol partical emission. Since most of us wear homemade masks, the question is: now what?

The study shows that how a homemade mask is put on and how it is used both impact particle emission: the more friction of the material,the more emission.  Furthermore, we now know that the double layer cotton masks are the best in reducing larger particles. Therefore, the researchers who executed this study conclude that wearing such a double layer mask can help in mitigating pandemics associated with respiratory disease, such as Covid 19. They also highlight the importance of regular changing of disposable masks and washing of homemade masks and suggests that special care must be taken when removing and cleaning the masks since they might be contaminated.


Wear a facemask. Put it on carefully and wear is carefully without touching it too much. Remove it carefully and throw it away or wash it after every use at 60 degrees or higher.

Create your own health!©