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Hi Ed, The regulation depends upon what safety and fire codes that you wish to be in compliance. There are a number of them out there, the most common being NFPA 45. Applicable portions of the NFPA code may be found on the index (home) page of http://www.safefumehood.com . Complete copies of the code are available for sale at http://www.nfpa.org . The question of expense to replace is a relative term. Complete retrofit alarms/monitors are in the $300-$495 range, and can be installed by a competent HVAC technician. Many universities use their facilities people to replace defective alarms and monitors. Based upon your situation, though, you may not be at the stage to replace your alarms. Here are some thoughts and questions. It's a good idea to annually check the face velocity displayed by your flow gauge against a handheld thermoanemometer or some other means of verifying actual face velocity. That will confirm whether the flow gauges are accurate and determine if a re-calibration is in order. You may just need to re-calibrate the alarms. Re-calibrate a few of these using new actual face velocities and see if they then have stable readings. Have there been changes to a lab's HVAC system that can start to effect monitor readings? Are these hoods on a VAV (Variable Air Velocity) system? If so, it would be correct that if some number of the total sashes are up, some of the monitors WILL begin to go into alarm. What make/model of alarms do you have? If you like, contact me directly, and I will arrange to have you talk to our technical people. No charge or commitment. Best regards, Tim Hawkins SafeFumeHood.com 1-888-327-4295 -----Original Message----- From: DCHAS-L Discussion List [mailto:DCHAS-L**At_Symbol_Here**list.uvm.edu] On Behalf Of Edward Senkbeil Sent: Thursday, November 19, 2009 4:13 PM To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU Subject: [DCHAS-L] Hoods The hoods (about 5 years old) in all our undergraduate chemistry labs are equipped with alarms which supposedly should go off with improper air flow. However many will continually alarm if the sash is pulled up by more than one third the way (below where sash has a normal catch about half way up). Is there any law / regulation which states that we must have the alarms working if they are part of the original equipment? All the hoods have flow gauges on them which are functioning, but we have been unable to get all the alarms to work properly. We are told it would be very expensive to get them all functioning. They become a problem in large student labs since they continually go off, and are distracting both faculty and students. We have considered disarming the alarm, but are concerned about any regulations we might be violating. Students are beginning to not pay attention to the flow gauges, but just automatically hit the mute button on the alarms. We believe the flow gauges are a more accurate reflection of any problems. Any comments or suggestions welcome. Ed Senkbeil, Ph.D. Chemistry Department Salisbury University
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