I had brought this up at Ask Dr.. Safety, and I wanted to follow up on the query. My laboratory is working on installing a microwave digester, and the manufacturer seems to suggest that venting the exhaust in a ductless fume hood would be okay. I am emphasizing that this would not be okay, but construction costs and city regulations on venting outside the building are causing a lot of obstacles in getting this digester installed. We will mostly be digesting with nitric acid, which should exhaust NO2 gas.

The main question is a) is it absolutely necessary to vent into a ducted fume hood, and b) if the exhaust is to be piped outside, should we install a series of scrubbers as well? The city may be concerned about venting gases to a mixed-zone industrial/residential neighborhood.

Best,

Andrew
--