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.

Workplace air isn’t always as safe as it looks. Dust, fumes, vapours and fine particles can be present at hazardous levels without being visible, which is why Respiratory Protective Equipment (RPE) is one of the most important and most misunderstood categories of PPE.




