Quantitative Face Fit Testing

The University Safety Office carry out quantitative fit testing with a PortaCount machine.

The PortaCount provides a direct assessment of respirator fit by comparing the concentration of ambient dust particles outside the facepiece to the concentration of particles that have leaked into the facepiece. The ratio of these two concentrations is called the 'fit factor'.

Since the microscopic particles in the air are not able to pass through the filter used on the face mask, any particles which are detected inside the facepiece are assumed to have come from a face-seal leakage.

The PortaCount uses a bespoke computer programme which runs an automated fit testing procedure which directly follows the HSE prescribed testing protocol in its guidance document INDG479. The software controls the test sample timing, test exercises and pass levels and allows the operator to input candidate / mask specific information. If the resultant fit factor meets the prescribed levels then a pass is achieved and the wearer is safe to use the RPE tested. Data in the form of Fit Test Records can be printed as individual reports showing all results achieved or selected on the basis of a number of parameters including test date or location.