Fig. 3

Schematic presentation of the equipment Almstrand et al. [22]. Participants inhale thorough a HEPA filter and exhale into the equipment. The box containing the equipment was maintained at approximately 36 °C. An optical particle sizer and an impactor allowed for counting and sampling of exhaled particles. Exhaled air that was not directly drawn into the impactor and counter was buffered in a reservoir and subsequently drawn into the impactor and counter and replaced by humidified particle-free air. Particles < 4.6 μm were sampled and the size distribution determined. By permission of the author