Face masks

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Hudson mask



ΕΤΥΜΟΛΟΓΙΑ United States NIOSH have 3 standards: Not oil resistant (N), Oil resistant (R) and oil proof (P) along with the percentages, gives rise to notation, N95, etc.

European standard, EN 149, defines "filtering face pieces" based on a filter penetration limit (at 95 L/min air flow) of three levels, FFP1-3 at levels of at least 80%, 94% and 99% respectively.

Surgical Masks

  • Prevents large droplets, but not smaller airborne droplets or aerosolised particles
  • Loses protective barrier once moist (within 20-30 minutes)
  • No face-tight seal, so infective particles can enter through gaps
  • May protect the wearer from the patient rather than vice versa. The evidence that surgical masks reduces infections in clean surgery is not convincing.[1]


  • N95 standard (although this is US standard)
  • 95% of 3 micron particles using NIOSH protocol.[2]


  • FFP3 disposable respirator (filters at least 99% of airborne particles and <2% inward leakage). Needs to be fitted as standard includes testing of inward leakage between the mask and face. This is European standard EN149:2001.

Service Respirators

Contain a particle (e.g. a HEPA filter) and charcoal filter. Hoped to be effective against a variety of lethal agents.