|During a pandemic, the reaction time to avoid contamination is crucial. One of the easiest ways to enhance protection is to wear an effective surgical mask or, preferably, a filtering half mask. Now, it is taking too long to bring this type of mask onto the market. Indeed, in addition to the production of the mask, it must be certified before.
This certification, according to the EN14683 standard, guarantees the filter efficiency of the surgical mask, but also its breathability. This certification, according to this standard, extends the time to market, which poses a real problem in times of pandemic.
In the RESERVIST project, we have tried to find an alternative testing protocol, as far as filtration efficiency is concerned, in order to reduce this time and to be able to put the masks on the market more quickly.
Testing for breathability is quick, but the bacterial efficiency test (BFE) can take at least 48 hours, and it is this time that we would like to reduce. To do this, we have made correlations between BFE and breathability on the one hand and between BFE and a paraffin filtration efficiency test which is described in the EN 149 standard for FFP masks, on the other.
Concerning these correlations, we could notice that the relation between the breathability and the BFE was not particularly conclusive. Indeed, we obtained a correlation r= 0.4215, which is not very high.
On the other hand, the correlation between the BFE and the paraffin filtration efficiency is much better. It reaches an r = 0.7173, showing a very good relationship between these two parameters. These results suggest a good alternative to the BFE test. Indeed, the paraffin filtration efficiency test is fast (1h), reproducible, and shows a good correlation with the BFE. These data will be further refined during the rest of the RESERVIST project.
A new test, with size-resolved DEHS (Di-Ethyl-Hexyl-Sebacat) aerosol penetration, has also been developed. This test overrides the high level of inherent variance of EN 14683 and also the dependence on the size distribution of the aerosol challenge of EN 149. Theoretical comparison of the new test to EN 14683 and to EN 149 has been carried out, and it is expected that a comparison with actual BFE tests will follow during the rest of the RESERVIST project.