[Dale M.]

Originally Posted by Dennis Brady

I think there are way too many variables for any formula to be more than a SWAG (Scientific Wild Assed Guess). Probably the only sure way to confirm a system works properly is with a smoke test.

I'm selling fans and working on designing possible ventilation packages for sale. In the past couple of weeks I've talked to several companies that manufacture fans and ventilation equipment. None had ever heard of the 125 rule. Where did it come from?

IT was adopted on ISGB forum first by Vince, than Mike copycatted it. It's the specification for industrial class A fume hoods.....

Here is a couple of sources of the 125 number..

http://www.pao.gov.ab.ca/?file=healt...de-of-practice
http://www.tamhsc.edu/departments/fi...fumehoods.html

IF you want bigger numbers....

http://www.isgb.org/info/safety/uploads/swsafety.pdf

Here is just some interesting data..

http://www.lni.wa.gov/Safety/Topics/...ault.asp#Hoods
http://www.hartandcooley.com/flex/ai...ion_chart.pdf/
http://www.engineeringtoolbox.com/ex...ds-d_1036.html
http://www.engineeringtoolbox.com/ve...tems-t_37.html
http://www.esmagazine.com/CDA/Articl...00f932a8c0____

And something to play with...

http://www.freecalc.com/ductfram.htm


Dale