With you in the room, bacteria counts spike

n an interesting new study, Yale Researchers say findings might help efforts to improve indoor air quality. According to the recent research a person’s mere presence in a room can add 37 million bacteria to the air every hour — material largely left behind by previous occupants and stirred up from the floor . Many previous studies have surveyed the variety of germs present in everyday spaces. But this is the first study that quantifies how much a lone human presence affects the level of indoor biological aerosols. The research team measured and analysed biological particles in a single, ground-floor university classroom over a period of eight days — four days when the room was periodically occupied, and four days when the room was continuously vacant. At all times the windows and doors were kept closed. The HVAC system was operated at normal levels. Researchers sorted the particles by size. Overall, they found that “human occupancy was associated with substantially increased airborne concentrations” of bacteria and fungi of various sizes. Occupancy resulted in especially large spikes for larger-sized fungal particles and medium-sized bacterial particles. The size of bacteria- and fungi-bearing particles is important, because size affects the degree to which they are likely to be filtered from the air or linger and recirculate, the researchers note. See more via Yale.