Kim, Yep, I know. I've been a member of both ACGIH and ASHRAE for years and have watched with growing concern ASHRAE's steady slithering into the industrial area. In their 1980s and early 1990s ASHRAE 62 standards, they clearly stated that as soon as there were toxic contaminants in the air, the appropriate standards were ACGIH ones. Then the referral got weaker and weaker and today ACGIH is a footnote in a table in ASHRAE 62.
They also have designs for some industrial systems that are not really good. For example, have you looked at the difference between a slot hood as designed by ACGIH vs. one designed by ASHRAE? The ACGIH version makes a smooth transition from the 45 o angle entry section into the round duct with no changes in the direction of air flow to create turbulence and noise. The ASHRAE version has a section at the top of the angle entry which comes forward and has a flat metal section just below the duct against which the air is drawn. And the duct is always too large in diameter to provide the required centerline velocity. The ASHRAE versions are noisier and less efficient due to the changes in air flow direction at the top and the lazy duct will allow particle settling if the duct is used for anything but gases and vapors. It's cheaper to fabricate, but not worth it for the loss in quality.
I also do not recommend using the ASHRAE 62-2004, 2007 or 2010 standards. Their fresh air requirements are too low. (Yes, I know they have a rationale for this, but run the numbers.) My reports always recommend using the fresh air requirements in 62-2001 plus some of the better placement of supply diffusers and exhaust grilles suggested by the later standards. Sometimes I get my way, sometimes not, but at least my position will be clear when the building has air quality problems later. ASHRAE is doing the same dumb thing they did during the energy crisis in the 1970s, only this time they are calling it LEED and Green.
Regarding the ASHRAE Class 4 definition and heat wheel recommendations, the problem with calculating the level at which recirculation of a certain contaminants is permitted does not fully appreciate the situation I have in art schools where the air is likely be recirculatable under their definition for a while, and then clearly too hazardous a moment later when they use more toxic materials. For example, I cannot have even small amounts of diioscyanates wending their way over and over through the recirculating system for the whole wing of an art school.
And the ASHRAE standard should be stricter than ACGIH because ACGIH standard is clearly limited to protection of healthy adult workers. ASHRAE is for the general public including students. The writers of ASHRAE 62-2001 understood this difference and suggested a guideline of 1/10th of the TLV for airborne substances for which there were no other established limits. That recommendation is also gone now, replaced by some vague statement saying that there should be further studies of these contaminants. Yeah, let's just wait to design our systems until that happens!
So I use the 1/10 TLV standard for schools in some cases because we have ADA, pregnant women, and other high risk students in the population by law. We even have high risk elderly malcontents like me wandering about the building.
Well, thanks, Kim. I feel better now.
In a message dated 6/22/2011 8:17:17 AM Eastern Daylight Time, kauletta**At_Symbol_Here**NOTES.CC.SUNYSB.EDU writes:
I'm not sure if this is the rule she was referring to, but on my other list, someone posted a copy of the ASHRAE 62-2004 letter of interpretation for acceptable cross leakage for energy recovery ventilation:
"Summary: ASHRAE 62-2004 provides clear guidance and clarification to air stream recirculation issues and defines air classification categories. With respect to recovering energy from exhaust air, the amount of acceptable exhaust air cross leakage is now quantified based on the contaminant concentrations of the exhaust air."
It does not specifically prohibit this technology for labs, but does say:
"Class 4: Air with highly objectionable fumes or gases or potentially containing dangerous particles, bioaerosols, or gases at a concentration high enough to be considered harmful, not suitable for recirculation or transfer to any other space.
Examples: paint spray booths, laboratory fume exhaust, kitchen grease exhaust."
Lab Safety Specialist
Stony Brook University
EH&S Web site: http://www.stonybrook.edu/ehs/lab/
Remember to wash your hands!
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