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EPA Building Air Quality Guide-1991

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Page 132 of 227

HVAC Systems and Indoor Air Quality 121 Appendix B: HVAC Systems and Indoor Air Quality This appendix provides information about specific HVAC system designs and components in relation to indoor air quality. It also serves as introductory material for building owners and managers who may be unfamiliar with the terminol- ogy and concepts associated with HVAC (heating, ventilating, and air conditioning) system design. Further detailed informa- tion can be found in ASHRAE manuals and guides and in some of the guidance developed by other trade and professional associations. (See Guidelines of Care Developed by Trade Associations in Section 5.) Additional information can be obtained using Appendix G or through discussion with your facility engineer. BACKGROUND All occupied buildings require a supply of outdoor air. Depending on outdoor conditions, the air may need to be heated or cooled before it is distributed into the occupied space. As outdoor air is drawn into the building, indoor air is exhausted or allowed to escape (passive relief), thus removing air contaminants. The term "HVAC system" is used to refer to the equipment that can provide heating, cooling, filtered outdoor air, and humidity control to maintain comfort conditions in a building. Not all HVAC systems are designed to accomplish all of these functions. Some buildings rely on only natural ventilation. Others lack mechanical cooling equipment (AC), and many function with little or no humidity control. The features of the HVAC system in a given building will depend on several variables, including: ■ age of the design ■ climate ■ building codes in effect at the time of the design ■ budget that was available for the project ■ planned use of the building ■ owners' and designers' individual preferences ■ subsequent modifications HVAC systems range in complexity from stand-alone units that serve individual rooms to large, centrally controlled systems serving multiple zones in a building. In large modern office buildings with heat gains from lighting, people, and equipment, interior spaces often require year-round cooling. Rooms at the perimeter of the same building (i.e., rooms with exterior walls, floors, or roof surfaces) may need to be heated and/or cooled as hourly or daily outdoor weather conditions change. In buildings over one story in height, perimeter areas at the lower levels also tend to experience the greatest uncontrolled air infiltration. Working with the electrical components of an HVAC system involves the risk of electrocution and fire. A knowledgeable member of the building staff should oversee the inspection of the HVAC controls.

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