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A building’s HVAC system is designed to perform several tasks: filter, cool, heat, humidify, dehumidify, pressurize, and/or exhaust. Each of these tasks affects indoor air quality. For example, if incom­ing air is not properly filtered, excessive dust from the outdoors is drawn into the building. If supplied air is not conditioned or heated satisfactorily, occupants may experience thermal discomfort. If supplied air is not dehumidified appropriately, excessive relative humidity levels may promote microbial growth. If patient isolation rooms are not properly pressurized, unwanted airborne transmis­sion of pathogenic bacteria may occur. If airborne chemicals are not properly exhausted from laboratories, these chemicals may migrate into nonlaboratory spaces. These are just a few examples of how the performance of the HVAC system can affect indoor air quality.

To effectively address mechanical system concerns, health care engineers should be aware of the corresponding indoor air qual­ity (IAQ) issues. A chapter in the Mechanical Systems Handbook for Health Care Facilities provides basic information regarding several key indoor air quality issues for the health care engineer. Several common mechanical systems concepts (such as building pressurization, moisture, filtration, and local exhaust) are reviewed from an IAQ perspective. By studying the chapter, the health care engineer should better understand how mechanical systems can affect indoor air quality.

Excerpt from: Mechanical Systems Handbook for Health Care Facilities
J. Robbin Barrick, PE, and Ronald G. Holdaway, PE
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