Date: Tue, 22 Jan 2008 15:23:55 -0500
Reply-To: List Moderator <ecgrants**At_Symbol_Here**UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: List Moderator <ecgrants**At_Symbol_Here**UVM.EDU>
Subject: Re: Low flow hood selection
Comments: To: SAFETY ,
"C2E2-L: C2E2 discussion list"

Last week, I asked the three lists above about people's experiences  
with low flow fume hood selection. I got responses from all three  
lists with a mix of answers that indicated that this is clearly a hot  
topic. I've appended many of the answers below. Some people have gone  
ahead and made their choices as to which low flow hood makes sense for  
them, some are sticking with good design of traditional hoods, others  
are testing low flow hoods side by side to make a more informed  
decision. It sounds like a good topic for a symposium at a number of  
national meetings (ACS, AIHCE, CSHEMA among others).

One thing that I noticed about low flow hoods is that the need for  
educating workers about working deep into the hood remains. In fact,  
several of the low flow hoods are specifically designed around deeper  
hood use than we often observe here.

Thanks to all for their responses.

- Ralph
From: dennis.compton**At_Symbol_Here**OBIRES.COM
Subject: Re: [DCHAS-L] Low flow hood selection
Date:  January 17, 2008 9:12:05 AM EST (CA)

When we were building our facility we explored the low flow hoods as  
well. Labconco allowed us to visit their testing facility and  
performed the ASHRAE tests on a hood that they let me clutter up.  
There were no abnormalities and the hoods are really well designed.  
They even allowed us to test their hoods below minimum specifications  
because I asked and I liked the results, but can't go into the details  
because it was non-standard. The primary issue with the Labconco  
Xstream hoods is their depth. They are approximately 40 inches deep  
versus the 36 inches of a normal hood. We had the space so this was  
not an issue. If you have a small room those 4 inches might become an  

We did look at the other models and the reason for selecting Labconco  
came down to the simplicity. The air flow has to go down before it  
goes up and that is why they need the extra space. They accomplish  
this by having a solid baffle with a gap on the bench top that you  
don't see behind the top to bottom slotted front baffle. This creates  
a laminar flow straight back. We liked this design because you don't  
have to worry about the moving parts on adjustable baffles being  
clogged up over the years and stop moving 5 or 10 years down the road.  
I would recommend having the sales reps for all of your design  
considerations come out and meet with you and then go tour the company/ 
s before you make your final choice. We were only purchasing 15 hoods,  
but all companies under consideration treated us well and did a good  
job at describing why they designed their hoods. Regardless of your  
final choice I highly recommend a low-flow hood because the energy  
savings is tremendous. The estimated pay-back in reduced heating and  
cooling bills for our facility is 16 months.


Dennis R. Compton, Ph.D
Director of Chemistry
Obiter Research, LLC
2809 Gemini Ct
Champaign, IL 61822
Phone (217) 359-1626

From:  david.gillum**At_Symbol_Here**
Subject:  Re: Low Flow Chemical Fume Hoods
Date:  January 2, 2008 3:19:32 PM EST (CA)

Hi Ralph,

We haven't begun using these units. However, our new Earth Sciences  
building will have 25 new low-flow units installed. I'll let you know  
how that works out!

Right now I believe it's a choice between three:

Lab Crafters - Air Sentry
Safe Air

Best wishes,


From: drhaugen**At_Symbol_Here**
Subject: RE: [DCHAS-L] Low flow hood selection
Date: January 17, 2008 1:20:59 PM EST (CA)

I have to stress two other options: Kewaunee Dynamic Barrier and  
Kewaunee LV.  The Dynamic barrier fume hood has about half the flow of  
most high efficiency units; the LV is of comparable flow to other high  
efficiency units.

I don't want to get into a commercial message here, but you can give  
me a call to discuss.

Dr. Bob Haugen
704 871 3214


From: KOCHW**At_Symbol_Here**
Subject: RE: [DCHAS-L] Low flow hood selection
Date: January 17, 2008 8:39:42 AM EST (CA)


We just installed 3 low flow hoods for the purpose of evaluating them  
for future projects.  Unfortunately, we are just now going through  
commissioning (includes ASHRAE 110) and have no results to share, yet.  
I suspect it will be 6 months to 1 year before we have any data worth  
sharing.  Once we have results, we will be publishing them...assuming  
our attorneys will allow us.  We are installing Air Sentry, Flow Safe  
and Kewaunee low flow hoods.

They all appear acceptable based on our initial research.  I believe  
Air Sentry and Flow Safe are discussing patent rights, which may have  
become a legal issue.  I think that is part of the reason we chose  
both Air Sentry and Flow Safe.  If you want more information, the best  
person to contact is Phil Lewis, our Industrial Hygiene Manager.  He  
has been working more directly on this project and gave a presentation  
on low flow hoods at our 2006 ACC EH&S Director's meeting.  Best of  

Bill Koch
Associate Vice Chancellor
Environmental Health, Safety, Parking & Transportation

From: kumar**At_Symbol_Here**WPI.EDU
Subject: RE: Air Sentry hoods
Date:  January 10, 2008 9:31:38 AM EST (CA)

Instructions for Air Sentry Fume hoods at WPI - Goddard Hall Lab

The Air Sentry Fume hoods at the WPI Goddard Hall Lab are set-up to  
operate safely at a face velocity of 50- 60 PFM when the sash is at  
the 50% open position by use of vertical rising sash at 14" or  
horizontal glass at maximum open position. Due to exhaust fan  
capacity, make-up air requirements and a high fume hood concentration,  
the air system is at its maximum capacity if all the hoods are opened  
to the 50% position or beyond.

Exceeding the 50% opening limit will increase the Low Alarm  
conditions. Students and users should be urged to never exceed the 50%  
maximum open requirement or operate in a hood which has alarmed. When  
the Vortex control face velocity monitor alarms, the Green "Normal"  
light is replaced with the red "LOW ALARM" light and should be  
accompanied by and audible alarm unless the user has defeated it. (1  
press of the mute button silences the alarm 1 time and 2 presses  
silences permanently. This is indicated by the yellow light on at tall  
times.) The Low Alarm is an indication that the air moving into the  
fume hood has reached a low level and there is a risk of loss of  
containment with-in the hood. The user should immediately reduce the  
open sash area. This may be accomplished by slowly closing the rising  
vertical sash and/or closing the horizontal sliding glass panels. This  
will increase the face velocity back to the Normal range and the red  
alarm warning light will automatically clear and the green Normal  
status light will turn on when a safe condition is achieved.

GH109/110 was designed with the expectation that the fume hood sash  
could be fully opened upwards to place and move equipment and  
apparatus, and then kept shut during experiments--using the sliding  
glass panes to access interior areas as needed. Following this  
practice guarantees that the hoods will be at least 50% shut during  
the experiments (presumably when fumes are produced) and maintain  
protective air flow.


From: 	rmizzo**At_Symbol_Here**PRINCETON.EDU
Subject: 	Re: [C2E2-L] Low flow hood selection
Date: 	January 17, 2008 11:50:19 AM EST (CA)


I don't have significant experience with 60 fpm hoods, but we have  
been evaluating several options for the desing of our new Chemistry  
building under construction.  We currently have 4 different hoods  
installed in the two organic chemistry labs that have the most use of  
volatile chemicals and have been evaluating them for several months.   
The lab workers have been using them and all testing was done with  
their equipment and chemicals in the hood.

We chose the labs based on their chemical use and the fact that the  
labs are big and get a lot of traffic around the hoods.

- Air Sentry:  We've had problems with their automatic sashes.  Ours  
will not pass ASHRAE tests at 80 fpm.  Even at the higher face  
velocity, when the auto sash works, it does result in energy savings.

- Waldner hoods with "Secu-Flow" technology is fantastic.  It passed  
all of our tests and more of their own fully open at 30 fpm!  It uses  
directional airflow inside the hood to increase the efficiency and  
effectiveness.  They have no installations in the US yet, but are very  
popular in Europe.  The design is wonderful and the users love it.   
They use a newer automatic sash technology that is superior to any  
we've tried.  On the negative side, the weak dollar makes them much  
more expensive than the others we've evaluated.

- Thermo-Fisher Concept hood - users seem to like it.  Ours passes the  
ASHRAE test with the sash fully open, operating at 60 fpm.  They use  
the same automatic sash technology as Waldner.  The only training  
needed is to explain the meaning of the alarms on the hood, otherwise  
they are quite user-friendly and even first-year graduate students can  
figure out how to disable the automatic sash (for demonstration  
purposes, it was set to close after 30 seconds, which was annoying).   
On the negative side, since the automatic sash device is new, the hood  
fitted with it has not yet been UL approved.

Of note - we have the same hoods without the auto sash operating at 80  
fpm in another lab building.  After three years, we've not had any  
problems with them and the users are happy with them.

- BedcoLab low-flow good.  Excellent capture, passed all tests  
including ASHRAE fully open, operating at 60 fpm.  Functions as well  
as the Thermo-Fisher hood, but we are not crazy about the design of  
the airfoil and the back of the hood is constructed such that the back  
panel is at an angle. This could limit the use of tall equipment,  
although the monkey bars at the back of the hood are of an acceptable  
height.  This is a Canadian company, so again, the weak dollar could  
affect the cost, although they are quite competitive with Thermo-Fisher.

One more thing...many of the automatic sashes are set to automatically  
open when approached.  Our biological labs like this, but the  
Chemistry labs don't.  The Chemists like to be able to view their  
experiments with the sashes closed. Or so they tell us.  Not that I  
see many sashes closed!  The auto-open is especially annoying when you  
have hoods in a row with traffic around them - people walk by and they  
open.  The newer auto-closers have sensors that stop a hood from  
closing when something is encountered - even a thin pipette is enough  
to stop it before it closes and breaks it.  The lab workers appreciate  
it, as the original auto-sashes tended to close on them if they  
weren't moving enough.  The PIs considered putting sharp edges as an  
incentive to keep the lab workers moving.  :)

Hope this helps.


Robin M. Izzo
Associate Director, EHS
Princeton University
609-258-6259 (office)
609-865-7156 (cell)

Service to others is the rent you pay for your room here on earth
- Muhammad Ali

From: tjs1**At_Symbol_Here**
Subject: Re: Low flow hood selection
Date: January 17, 2008 10:43:12 AM EST (CA)

Hi, Ralph.  I personally don't know of any EHS folks who have  
evaluated the various types of Low Flow hoods.  We have, on numerous  
occasions, invited the manufacturers of several types of low flow  
hoods to loan us one of their models to we can evaluate it in our  
environment.  They have all refused to do so.  What we wonder, is what  
are they hiding???  If they have such a great product, why wouldn't  
they allow a big institution that might buy hundreds of their hoods to  
test drive one??  We even offered to do our own installation in a test  
lab here at Cornell, at our own expense, and still got turned down.

We currently have a ban on low flow hoods and are not allowing any to  
be installed at Cornell.  We have a really good, energy efficient,  
less expensive VAV paradigm in place and none of the low flow hood  
guys have been able to demonstrate that we will have lower costs or  
save more energy with their systems.  I would be very interested in  
hearing of your decisions and/or the comments of other responders to  
your query.  See my additional comments below.

Take care.  Tom

Below is an off-list response to Peter Doob at the FDA re low flow  
hoods.  This was in response to a question from Peter on another  
mailing list, from a couple of weeks ago:

2)  We have not approved the installation of any variety of the "low  
flow" or "high efficiency" hoods.  Once again, we are very dubious of  
the claims of performance from the various manufactures.  Snake oil  
salesmen.... First off, there is no substantive energy savings that  
anyone has been able to demonstrate to us.  Many of the low flow  
systems are actually function as CV hoods.  First costs are high--up  
to 20 percent more per unit--and we still have to add on our own  
controls, etc.  And there is no demonstrated safety benefit.  In fact,  
with the low flow hoods, a substantial behavioral change is needed to  
use some of these units safely--working back further in the hood,  
removing your arms slowly to strip vapors off your lab coat sleeves,  
lower ability to contain a bigger spill, etc., etc.  And we all know  
how behavioral change goes in the lab culture....  So, we are actively  
resisting various A&E firms that are trying to install various models  
of "low flow" hood in our new buildings.  We are using mostly Fisher- 
Hamilton restricted bypass hood shells with full VAV (Phoenix, Air  
Monitor, ACL Web enabled technology) with room and hood set backs.    
We have developed our own sequence of operations and our Control Shop  
guys are heavily trained to monitor and maintain our new and existing  
systems.  So we are probably not going the low flow hood route anytime  

Tom Shelley,   Laboratory Ventilation Consultant
Environmental Health and Safety Department
Cornell University
395 Pine Tree Road, Suite 210
Ithaca, NY 14850
607 254-8300 (message at H&S)
607 342-0864 (cell)


From: 	tbechta**At_Symbol_Here**
Subject: 	Low flow fume hoods at UMass Amherst
Date: 	January 18, 2008 2:03:57 PM EST (CA)

Hi Ralph:

We are in the process of installing over 100 low flow fume hoods in  
our new science building (Fisher Hammilton).

We have installed Air Sentry (VAV) and Labconco (CAV) Hoods as trial  
in another lab

We used the modified ASHRAE 110-1999 NIH standards for testing the  
hoods.  We will be using this standard to test 10% of the hoods on  
each floor.  With standard testing for 100% of the fume hoods.

We will be balancing the hoods at approx 70 fpm because of the  
accuracy of the controls in the HVAC and looking at what velocities  
should you use to fail the fume hoods, as well at what flow do you  
cause the hood to go into alarm.

Hope this helps and if you have any questions please feel free to give  
me a call.
Terri Bechta

Theresa W. Bechta
Hazardous Materials Inventory Control Manager
Environmental Health and Safety
117 Draper Hall
University of Massachusetts
40 Campus Center Way
Amherst, MA 01003-9244
ph: 413-577-3632    fax:413-577-3634


From: chaosforthefuture**At_Symbol_Here**
Subject: Low Flow Hoods
Date: January 17, 2008 9:31:26 AM EST (CA)

Hi Ralph,

being the resident safety heretic that I so often am here are some  
things I am working on here at RPI

1. I don't believe the ANSI hood test is appropriate and am trying to  
switch over to the way NIH does their hoods where they measure what is  
known as Turbulence Intensity (TI). Based on the studies I have  
reviewed TI is a much better predictor of performance of a hood.  
Attached is the TI testing protocol - I am modifying it slightly so we  
don't need a tracer gas and can just use multiple anemometer  

2. If you are using low flow hoods you might want to try and introduce  
some sort of control banding into your system. I think we way overuse  
hoods in the labs because we are scared death of liability and are too  
reticent to make a professional hazard and risk assessment of what is  
actually going on in the lab. The advantage of control banding is one  
can get the lower risk experiments in a room where you could use low  
flow hoods or no hoods at all. I recently went through one building  
and my hazard/risk assessment of what they were doing in the rooms  
showed that at most only two labs really needed hoods. My ultimate  
dream here at RPI is to have almost no energy used for hoods and  
perhaps have one building or one room per floor where a real hood and  
filter system is used - I keep looking at the experiments and trying  
to come up with ways to capture/filter the material at the point of  
generation or prevent airborne generation altogether - a bit quixotic  
I guess :)

Just my thoughts


Peter Collopy, CIH, CHP, CSP
Director, Entropy Control
Chaos for the Future
129 Second Street
Troy, NY 12180

Previous post   |  Top of Page   |   Next post

The content of this page reflects the personal opinion(s) of the author(s) only, not the American Chemical Society, ILPI, Safety Emporium, or any other party. Use of any information on this page is at the reader's own risk. Unauthorized reproduction of these materials is prohibited. Send questions/comments about the archive to
The maintenance and hosting of the DCHAS-L archive is provided through the generous support of Safety Emporium.