Many new hospitals, educational facilities, and air quality sensitive production facilities are being constructed to have little or no fiberglass in the airstream. Some of this surge in particle-free duct systems comes from new research on the effects of fiberglass erosion and microbial growth on inhabitants, and it is making more and more designers wary of fiberglass in the airstream. As the production of microprocessors becomes more sensitive, the more crucial it is to have a "clean air" room for production. In addition, processes involving caustic fumes often need silencers without organic compounds in their fume hood exhaust stations because the fumes would react adversely with the acoustical fill.