To determine how well the mask material can filter small particles, that may potentially be harmful.
- ATM 226 Aerosol Generator
- PortaCount Pro 8030 Particle Counter
Air containing small particles is drawn through the mask material. The small particles are created using an Aerosol generator with a sodium chloride solution in an otherwise HEPA filtered environment. Mask samples are then fitted in the setup in an airtight fashion so that air can only travel through the filter material.
A constant flow of air is drawn through the mask with a controlled flow setup with an estimated peak air velocity of 0.5 m/s. In this setup, this value would correspond to the volumetric flow specified in NEN 149. The particle concentration before and after the mask is determined by sampling the air with the particle counter. The filter capacity is then determined as the fraction of particles before the mask divided by the number of particles behind the mask; a higher filter factor indicates a better filter capacity.