Big thanks to everyone who sent their masks for testing. We received in total 139 masks from more than a hundred people. Among those were 115 reusable masks, 108 store bought masks, and 31 self-made masks. Unfortunately, a lot of masks did not include detailed information and consequently the results table contains many empty cells.
The properties of the masks varied widely. Emphasizing different properties of the masks -- the ability of the material to filter different particles (filtering ability), or the ease of breathing through the mask (breathability) -- allows us to rank them very differently. Figure 1 shows the ability of the masks to filter particles with diamteters 300 nm and 3000 nm. Each of the tested masks is represented as a dot on the plot. The size and color of the dots indicate the breathability of the mask: blue and large dots correspond the best breathability, red and small dots to the worst.
Masks with good breathability tend to be bad at filtering particles and typically capture less than 50% of 300 nm particles and less than 80% of 3000 nm particles. We also find masks which have both bad breathability and bad filtering ability represented by red dots at the left edge of the plot. These masks should be avoided. The best protection is provided by masks which simultaneously filter well particles of all sizes. These masks correspond to dots at the upper right corner of the plot. Luckily there are masks which combine a good filtering ability with a good breathability.
Figure 1. Filtering ability for 300 nm ja 3000 nm particles. Dot color and size represent breathability.
We tested both reusable as well as signle-use masks. Figure 2 shows that the filtering ability of reusable masks is varies in a wide range. Single use masks have overall consistently good properties although with a few bad outliers.
Figure 2. Filtering ability for 300 nm ja 3000 nm particles. Dot size indicates breathability. Blue dots correspond to reusable masks, red dots to single-use masks.
We received many self made masks. None of those were able to filter more than 50% of 300 nm particles. However some of the masks were able to filter 100 nm and 3000 nm quite well. (Figure 3)
Figure 3. Filtering ability for 300 nm ja 3000 nm particles. Dot size indicates breathability. Blue dots correspond to self-made masks, red dots to shop-bought masks.
The test results give a general overview of the filtering abitliy and breathability properties of available masks. The tests were not done according to a official standard procedure and the facilities used did not possess a certificate for testing. It is forbidden to publish these results without explicit written permission from the authors. The authors do not take any responsibility for any conclusions and/or opinions drawn from the results.