ASHRAE Addendum Addresses Recirculation of Air
Jul 24, 2003
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A proposed addendum to the American Society of Heating, Refrigerating and Air-Conditioning Engineers' (ASHRAE) ventilation standard that
limits recirculation of air in buildings has been approved for a fifth public review.

ANSI/ASHRAE Standard 62-2001, Ventilation for Acceptable Indoor Air Quality, sets minimum ventilation rates and other requirements for commercial and institutional buildings. Addendum 62y was approved for a fifth review at ASHRAE's 2003 Annual Meeting, June 28-July 2. Public review dates will be announced later this summer.

The proposed addendum adds a new section that defines four classes of indoor air and limits recirculation of lower quality air into spaces that contain air of higher quality. The proposed addendum would create requirements for recirculation of air, making it clear to designers what can and cannot be recirculated to where, according to David Butler, P.E., committee chair.

The foreword to the addendum describes the classifications and recirculation criteria, which are:
* Class 1: Air with low contaminant concentration and inoffensive odor and
sensory-irritation intensity, suitable for recirculation or transfer to any
* Class 2: Air with moderate contaminant concentration, mildly offensive
odors or sensory-irritation intensity. It also includes air that is not necessarily harmful or objectionable but which is inappropriate for transfer or recirculation to spaces used for different purposes.
* Class 3: Air with significant contaminant concentration or significant offensive odor or sensory-irritation intensity that is suitable for
recirculation within the same space. Class 3 air is not suitable for recirculation or transfer to any other spaces.
* Class 4: Air with highly objectionable fumes or gases or potentially containing dangerous particles, bioaerosols, or gases at a concentration high enough to be considered harmful, not suitable for recirculation or transfer within the space or to any other space.

The addendum does not address recirculation or transfer of air from smoking areas to no smoking areas.

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