I’ve been accused of being a copycat: http://www.lampworketc.com/forums/showpost.php?p=1909634&postcount=14
IT was adopted on ISGB forum first by Vince, than Mike copycatted it. It’s the specification for industrial class A fume hoods…..
Ummm…no, sorry Dale, but you are incorrect. Both Vince and I use the ACGIH (American Conference of Governmental and Industrial Hygenists http://www.acgih.org/home.htm ) recommendations for ventilation systems from their “Industrial Ventilation: A manual of Recommended Practice”. There is no “copycatting” going on here, just the usage of an internationally recognized organizations recommended practices. It is unfortunate that Dale chose to use the wording he did as it denigrates the work I do on behalf of lampworkers around the world.
Like NIOSH (National Institute of Occupational Safety and Health (part of the CDC) http://www.cdc.gov/niosh/ ), the ACGIH makes recommendations of recommended practices to organizations such as OSHA (Occupational Safety and Health Administration http://www.osha.gov/ ) which then takes those recommended practices and puts them basically into law.
Dale’s comment shows a clear lack of understanding of where the basis for the “rules” comes from, and his application of them is lacking because of that.
But the most amusing thing that I’ve found in reading over several threads on LE is my good friend Dennis Brady’s latest “business” interest: the design and sale of ventilation systems. From someone who considers the ACGIH’s recommended practices as a “scientific wild assed guess”, this of course comes as no surprise to me, but I do have concern for those who purchase ventilation systems from someone who has no background in ventilation, and no understanding of the principles of ventilation design.
Of specific interest are his comments a few months ago about oxygen concentrators. He was weighing in with his “opinion” on testing of the machines and made this erudite comment:
If we are to accept technical information as valid, it must come from an unbiased source that has no dog in the fight. Until some such source presents itself, it’s appropriate to treat all claims with healthy skepticism.
Later on in the same thread:
…My impressions from your postings (here and on all the other boards you’ve posted about your proposed comparison) is that your references will consistently favour the machines you sell and therefore will, and should be, viewed with some skepticism. It’s like Ford posting a database comparing vehicle performance. Personally, I’d be interested in reading a comparison done by the auto club – but I’d never trust one done by any manufacturer or one of their dealers. Especially if the comparison started by denigrating GM.
I like this one ALOT because I think it is going to come back to haunt him, especially in light of his comments about the ventilation system he is designing apparently based solely on smoke tests.
I ‘spect you’ll be equally amused by the smoke test videos demonstrating the erratic reliability of the 125 guideline.
The only reason there would be an “erratic reliability” of the 125 CFM per square foot guideline is its use in a poorly designed system. For example, Dennis’ own post:
A 12″ x 12″ hood with 125 cfm fan mounted directly over the torch might work great but would be pretty much useless 3 ft away.
The 125 figure is meaningless unless related to distance from fume source.
and this priceless gem:
The “formula” commonly recommended is 125 times the surface area of the hood but that is only a guideline. The closer the vent outtake is to the torch, the less fan capacity is needed to extract the fumes.
The kind of system you see the Italians using for glasswork is also the kind of system you’ll likely see in commercial shops that are carefully inspected and required to meet rigid safety standards. It may be different in different places, but where I live, the 125 guide is completely ignored. The only standard accepted is the smoke fume test that confirms extraction of all fumes.
The fume test is what is used to show that the “125” standard is actually taking place. It is the test, not the standard. Once again, a basic mis-understanding of what the basic principles of ventilation are.
It also ignores the principle that the entire flame plume is trapped by the hood by proper placement of the hood itself. Do people ignore this basic principle? Of course they do! However, that does not mean the “125” standard itself is faulty, it merely means that the ventilation system has not been properly designed and installed.
When reading Dennis’ words, keep in mind that he knows nothing about ventilation. Take his words with a grain of salt…after all, anyone who can write:
FWIW, how you control the incoming air is as important as how you exhaust. Too much inflow will hamper the effectiveness of your exhaust.
and actually BELIEVE it, is seriously out of touch with reality.