Laboratory experiments on indoor bioaerosol deposition onto various surface materials

Increasingly, people spend their time indoors and at the same time cases of unacceptable indoor air quality are on the rise. Poor indoor air quality has been shown to cause respiratory symptoms, irritation, and other short- and long-term health outcomes. Indoor air quality problems are usually complex and a sum of several factors or failures in the building or structures. Unbalanced or poorly maintained ventilation system induces uncontrolled air leakages through building envelope. In case of moisture damage, air leakages may transport microbial spores, smaller fragments and metabolic products from microbial growth inside building structures into indoor environment, surfaces and air. In BITEFA project, bioaerosol deposition on various surface materials and flow fields were studied with Penicillium brevicompactum spores in a duct form test chamber. The air velocities of the system were similar to those in ventilated apartment buildings. Three commonly used materials were placed on horizontal and vertical surfaces at various flow field locations in the test chamber. Deposition was measured with cultural based and digital microscopic methods. As expected, clear differences were observed on deposition rates which was highest for horizontal upward facing surfaces and lowest for ceiling with low air velocity. Results indicate that viable bioaerosol deposition rate is highly dependent on particle size, air velocity and air flow direction towards the surface. Smaller non-viable particles are available deposit on all surfaces, vertical and horizontal. Because of smaller size of particles, the gravitation is not the major deposition mechanism. Small particles deposit by interception and diffusion. This study gives more information on practice of surface bioaerosol sampling in indoor environment investigations.