I have a very large industrial building with a few concentrated sources of chemical air contamination. I am using local exhaust hoods to exhaust these areas at the source.
My question is what to use for the remainder of the building. When I take the air volume being exhausted from the point sources and apply an ACH calc to the total building volume it works out to be only about 1.5 ACH. Should I add additional ventilation to bump the total building ventilaion up to 3 ACH? I am in a Northern climate so energy usage is very high for high ventilation rates due to makeup heat.
for this valuable post!
OSHA 29CFR-1910-1450 Lab Standard provides information on permissible explosure limits (PEL), TLV's, requirments for worker monitoring, use of chemical fume hoods, and other critical information for lab Owners. This is designed to aide your design and enforcement of your OSHA mandated chemical hygiene plan. They also promulgate specific minimum fresh air (100% OA) ventilation rates for laboratories (which you have if you have chemicals being used with specific PEL's). They reference a 4-12 ACH and obviously no engineers get paid enough for designing to any minimum.
It sounds like you have a large building and going from 1.5ACH to 3ACH would present an operating cost burden. You may want to consider walling in the area that liberates the chemicals with which your worried--as a way to reduce to ventilation demands. Do your homework and don't enter into any discussion on ACH lightly. Remember, you're required by OSHA to monitor all employees exposure to any chemicals that warrant monitoring. This is black letter OSHA law
Consult a licensed industrial hygienist to ascertain your legal requirements for worker monitoring and examine ways to improve source capture and minimize exhaust/make-up