conveyance systems are currently in development by the National Air Duct Cleaners Association. However, the effectiveness of duct cleaning in controlling allergic disease is yet to be determined.

Research Agenda Item: Evaluate the role of duct cleaning in controlling allergic diseases.

As described throughout this report, ambient relative humidity is often considered a major controlling factor for indoor allergens. Control of relative humidity, or water vapor pressure in occupied space and in the HVAC system is an important part of allergen control in both residential and commercial buildings.

Research Agenda Item: Develop a public-use guideline on moisture and allergen control in buildings. The guideline should describe the proper use of vapor retarders and other techniques for moisture control in both naturally and mechanically ventilated buildings.

There are approximately 4 million commercial and 84 million detached residential buildings in the United States. About 75–85 percent of the buildings that will exist in the year 2000 have already been built. Maintenance, operation, renovation, and housekeeping practices affect the useful life span of a building and the quality of the indoor air. Cost effective strategies for source and exposure control are needed to address the problems associated with normal degradation of the HVAC performance that occurs as a building ages.

Research Agenda Item: Determine the relative efficacy of currently recommended environmental control strategies and develop cost-effective strategies for controlling aeroallergens throughout the lifetimes of residences and other buildings.



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