5/2/2011 SCHOOL COMMITTEE Minutes

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a a To maximize air exchange, the 1 DPH recommends that both supply and exhaust ventilation operate continuously during periods of occupancy. In order to have proper ventilation with a mechanical supply and exhaust system, the systems must be balanced t provide an"adequate amount of fresh air to the interior of a morn while removing stale air from the morn. It is recommended that HVAC systems be re-balanced every five years to ensure adequate air systems function SMAC A, 1994). The systems were reportedly last balanced upon completion of the building in 1996. The Massachusetts Building Code requires that each ro6m.have a minimum ventilation rate of 15 cubic feet per minute (cfm) per occupant of fresh outside air or openable windows (SBBRS, 1997; BOLA, 1993 . The ventilation must be on at all times that the morn is occupied. Providing adequate fresh air ventilation with open windows and maintaining the temperature in the comfort range during the cold weather season is unpractical. Mechanical ventilation is usually required to provide adequate fresh air ventilation. Carbon dioxide is not a problem in arra of itself. 'It is used as an indicator of the adequacy f the fresh air ventilation. As carbon dioxide levels rise, it indicates that the ventilating system is malfunctioning or the design occupancy ofthe morn is being exceeded. h n this happens, a buildup of common indoor air pollutants can occur, leading to discomfort or health complaints. The Occupational Safety and Health Administration (OSHA) standard for carbon dioxide is 5,000 parts per million parts of air(ppm).. w ri er may be exposed to this level for 40 hours/week, based on a time-weighted average (OSHA, 1997). The MDPH uses a guideline of 800 lnlnm for publicly occupied buildings. A guideline of a 600 ppm or less is preferred in schools due to the fact that the majority of occupants are young and considered to be a more sensitive population in the evaluation of environmental health 6