During preliminary research to choose a new supplier of FFP2 mask we found that 5 out of 7 (71%) of the FFP2 masks did not perform as expected and required by the EN-149 with a fail ratio in these mask between 23% and 82%. A surprising amount of these masks failed to even pass the FFP1 threshold of 22% leakage, which means that in 14-50% of HCWs these FFP2 masks actually performed just like a surgical mask that had an average leakage of 25% in our study. Futhermore, HCWs wearing a failing brand had a 22% risk of having a fitscore of 1 during at least one excercise. This means a 100% leakage, with no measurable concentration difference whatsoever between the inside and the outside of the FFP2 mask. If the mask passed the EN-149 norm, this risk was deminished to 1,7%. Although both men and women are affected with poor fitting masks, woman are up to 90% more likely to fail the fittest depending on the brand of mask. Futhermore we found from the questionnaires that if we were to rely solely on fit-checking alone, a self-test advised among others by NHS self-assessment guidelines, we would miss a little over half the failing masks.

.