The filter inside an FFP3 mask captures 99% of airborne particles, which is tested, certified, and printed on the packaging. What isn't printed is how much inhaled air bypasses that filter entirely through a gap at the seal.
The HSE sets FFP3 total inward leakage at a maximum of 2%. If it exceeds, the mask's protection is compromised regardless of its filter grade. This is why face fit testing is the only way to know the mask is working.
Filtration efficiency tells you how a mask performs in a lab. Fit determines how it performs on your face. Keep reading to find out why the seal matters more and what to do about it.
Does an FFP3 Mask Actually Protect You If It Doesn't Fit Properly?
No, and this is the most important thing to understand about respiratory protective equipment. An FFP3 dust mask is a sealed system. Contaminated air should enter only through the filter. If the face seal fails, unfiltered air bypasses the filter entirely with every breath.
The filter grade, including FFP1, FFP2, or FFP3, tells you how efficiently the filter handles particles that pass through it. It says nothing about the seal. A worker wearing a protective mask with a compromised seal receives only a fraction of the stated protection, and they won't know it.
A proper fit can make all the difference. Read our guide to FFP3 mask fit and find out how to ensure your respirator provides the protection you expect: https://www.respiratorshop.co.uk/blog/why-does-ffp3-mask-fit-matter-more-than-filter-rating