DCHAS,

I would like to "piggy-back" on this conversation a bit and also ask a question. We recently underwent a full control systems and alarm upgrade for all of our hoods on campus.  About 25% underwent a full hood replacement while the remainder had controls, VAV boxes, displays, sash sensors, and proximity sensors added or replaced. 

 

The plus side to this is that centrally, I can pop onto our BMS system and get an graphical representation of sash heights, flows, etc.  The downside is that now that we have functional alarms, they alarm a whole lot more (this is not actually a downside, but my researchers interpret it as such).  I have taken a two prong approach to this:

 

1.  If an exhaust fan serving the building goes offline or if there is a significant drop in static pressure within the ducts, our central plant gets an emergency alarm, including strobes, that a science or engineering building has a possible exhaust failure and facilities responds immediately.  The system automatically emails me as well, so that I can pop in and check on things either remotely or, depending on circumstances, in person. 

2.  Any lab-wide purge button use sends a notification to EHS. 

3.  For localized, low flow alarms on the hoods, the labs usually handle those.  They are trained to ensure that their sash is closed as soon as possible to 18" or below when in alarm.  If it continues to alarm, then a work order should be submitted for EHS and Facilities to look into the issue.   In actuality though, I have a few labs that simply mute the alarms constantly and continue working. 

 

My question is this:  We are pushing exhaust capacity limits in our chemistry building.  For my old school organic synthesis lab, they run columns all day, everyday.  Because of this it is very routine for the sash heights to be above 18" during column loading for extended periods of time.  This usually causes the hoods to be in alarm as they end up with a face velocity of 50-60fpm at those heights (our set points for alarms are 80fpm).  The hoods still maintain containment based on smoke testing, but the alarms are extremely uncomfortable for the labs and they end up muting them quite often.   Does anyone have thoughts or suggestions on this?  

 

 

 

Hi Monique!

 

There are many reasons alarms should have a customized instruction section.

 

For example, some constant volume low volume systems are set up at an 18" sash position and 60 FPM. When sash is raised all the way, the velocity alarm may go off as velocities for CV systems go down as sashes are raised. The relationship between face velocity and sash position is not intuitively obvious to many researchers and students.

 

Our fume hood instruction / safety PowerPoint can easily be appended with any slides explaining a unique exhaust system.

 

 

 

Thanks Bob!

 

We luckily, also found this out before our remodel.  Our faculty thought our previous hoods alarmed for low velocity when in actuality there were only high flow alarms.  However, I was not aware that you could get videos and such.  I will keep that in mind for the future.

 

Best,

 

 

Hi Monique!

 

If university departments have a policy on fume hood velocity alarms, most fume hood companies have instructional videos, PowerPoints, or manuals, into which these policies can be integrated before new hoods and accompanying operating literature are delivered. In the digital age, this requirement is not difficult for manufacturers to meet.

 

However, when fume hoods are delivered to a large project based on general specifications that do not include a requirement to provide specified safety and operation procedures, confusion by end users to alarm situations becomes inevitable.

 

 

 

Alarming when opened at the incorrect sash height or somehow not being used properly is to be left in alarm until they correct the situation.  Any fume hood not functioning properly, including alarms, are tagged out of service until the issue is resolved. 

 

Monique Wilhelm

Laboratory Manager

Department of Chemistry & Biochemistry

University of Michigan - Flint

 

From: ACS Division of Chemical Health and Safety [mailto:DCHAS-L**At_Symbol_Here**PRINCETON.EDU] On Behalf Of Penny Manisco
Sent: Wednesday, February 14, 2018 6:28 PM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: [DCHAS-L] Policy for Alarming Fume Hood

 

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