DEDICATED EXHAUST SYSTEM FOR LABORATORY HOODS
ISSUE:
Interpretation of what constitutes a dedicated exhaust system.
BACKGROUND:
For some reason, there have been misinterpretation by the consultants of VA's
requirements for dedicated exhaust systems for laboratory hoods.
DISCUSSION:
Exhaust from laboratory hoods is considered a special exhaust system. A special
exhaust system includes an independent exhaust fan and duct work not connected
to the general or other building exhaust system. A dedicated exhaust system
where specified for each hood, therefore should include an independent exhaust
fan and duct work just for that hood. A dedicated exhaust system, however can
serve more than one hood where permitted by the VA criteria.
RECOMMENDATIONS/CONCLUSION:
1. VA's HVAC Design Manual for Hospital Projects has been updated providing
further clarification on dedicated exhaust systems for various type of hoods to
avoid any confusion in the future.
2. In an existing building where it's not practical to provide a dedicated exhaust
system for each hood, several (3-4) hoods may be connected to a common
exhaust fan and duct work dedicated for these hoods. However, this scheme
would require an anti-backflow device for each hood to prevent reverse air
flow, and the exhaust fan should not be turned off.
FOR ADDITIONAL INFOR MATION:
Contact Satish Sehgal @ 202-565-5032, Kurt Knight @ 202-565-4980, or Sat
Gupta @ 202-565-5268.
18 FEBRUARY 1997
FM-187C-DA63
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