Collection of bacterial aerosols by means of slit-sampler: a face-mask study.

A simple experimental set-up, using a slit-sampler, was tried in order to measure the effect of wearing face-masks. During the experiments we discovered that when talking unmasked, the number of bacteria collected by the slit-sampler was considerably lower than the number actually spread. When speaking, the contamination spread was mainly in the form of bacterial clusters. These were not sampled on the agar plate but withheld in the sampling equipment (wall loss) or lost. The advantage of using a slit-sampler when comparing face-masks is discussed.