Published: Jan 2009
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HISTORICALLY, MANKIND BEGAN THE SAGA OF structure occupancy in caves, which were undoubtedly virtual gardens of mold, bacteria, and pests. As civilization advanced, indoor conditions became more and more hygienic, so that the Greeks and Romans lived in comparatively clean, dry environments. During the Middle Ages, however, hygiene was apparently forgotten. Rats, mice, cockroaches, and probably mold were allowed to proliferate in occupied environments, and straw was used to absorb all kinds of organic material on the floors of both castles and hovels. These conditions led to the black death (spread by rat fleas), exposure to intestinal bacteria and viruses, and the consumption of mycotoxins. During these times, outdoor air, in spite of rain, snow, and hail, was far healthier than indoor air. Today, rats and cockroaches are not normally permitted in our living space, and straw is reserved for barns (sometimes leading to allergic and possibly toxic diseases in farm animals). We have designed and built homes and work places that are clean and that may be more healthy than the outdoor environment. Our interiors can be kept dry, and mechanical ventilation allows filtration of all entering air, providing a refuge from the fungal spores, bacteria, and other particles in outdoor air. However, changes in construction practices and materials are introduced at a rate exceeding our current capabilities to evaluate their implications. There is evidence that housing units are becoming more tightly constructed, resulting in reduced air exchange rates. Water generated by occupants and water migration through slabs on grade can contribute to increased indoor humidity.
Burge, Harriet A.
EMLab P&K, San Bruno, California