From: Shannon Stoney (shannonstoney@earthlink.net)
Date: 07/22/01-09:54:28 PM Z
Joe wrote:
> To calculate the cubic feet per of the ventilation fan required is height X
> width X length X 33 = CFM of fan required. The actual amount of room air
> changes required by OSAH is found in the book of regulations. It's out
> there, someone simply needs to look it up.
We did find this out. Standards differ in the US and Canada as it turns
out. Here the standard, I think, is 12 air changes per hour, and in
Canada it is 15. The book I mentioned, Overexposure, cautions that these
are guidelines only. Smaller rooms may need more changes per hour, and
rooms with a lot of people working and lots of trays out also need more.
Our darkrooms are very busy with lots of people working in them all day
long.
Also, someone told me that the real issue is not so much air changes per
hour as it is the velocity with which the air is being sucked out. This
ventilation engineer told me it should be about four miles per hour.
--shannon
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