As health and school officials deal with a second wave of the H1N1 virus, new information is available on health consequences of exposure to such airborne infectious diseases and the implications on the design, installation, and operation of HVAC&R systems.

“While the long-standing public health view is that influenza transmission occurs through direct contact or large droplets, newer data suggests it also occurs through the airborne route, meaning HVAC&R systems may contribute far more to transmission of the disease and, potentially, to reduction of that same transmission risk,” says Gordon Holness, president of the American Society of Heating, Refrigerating and Air- Conditioning Engineering (ASHRAE) that developed the guidance.

ASHRAE’s Airborne Infectious Diseases Position Document addresses the impact of ventilation on disease transmission, the disease for which ventilation is important for either transmission or control, and the control strategies that are available for implementation in buildings. The paper can be read at <www.ashrae.org/positiondocuments>.

Airborne transmission through building ventilation systems can be significantly reduced by provision of adequate air filtration and pressurization, says Holness. ASHRAE’s other guidance of relevance includes Standard 170, Ventilation of Health Care Facilities, and Standard 611, Air Quality Within Commercial Aircraft.