1. US NFPA (National Fire Protection Association) Standard 45
The NFPA 45 standard is the US Standard on Fire Protection for Laboratories Using Chemicals.
The previous version of this standard, NFPA 45-2004, had no actual requirements on Lab ACHs,
although in the non-binding appendix of the standard there were some recommendations relating
to lab ACHs that in the past had been sometimes used as a design practice. The text of these
recommendations was as follows:
A.8.2.2: A minimum ventilation rate for unoccupied laboratories (e.g., nights and weekends) is
four room air changes per hour. Occupied laboratories typically operate at rates of greater
than eight room air changes per hour, consistent with the conditions of use for the laboratory.
It is not the intent of the standard to require emergency or standby power for laboratory
ventilation systems.
However, this text and any mention of specifying lab ACHs was eliminated in the current NFPA 45
– 2011 standard that just recently issued:
A.8.2.2: It is not the intent of this standard to require emergency or standby power for
laboratory ventilation systems.
The only remaining reference to lab ventilation is as follows which did not change between the
2004 and 2011 versions and does not provide any prescriptive rates:
8.2.2* Laboratory units and laboratory hoods in which chemicals are present shall be
continuously ventilated under normal operating conditions.
As such with the 2011 version, NFPA is now silent on prescribing any lab air change rates other
than to require continuous ventilation.