For example, the Harvard Green Campus Initiative began posting “Shut the
Sash” magnets at each fume hood, which
state that leaving the fume hood open
uses 3. 5 times the energy of a house (see
Figure 1). Allen Doyle, of the University
of California–Davis, sticks Post-it® notes
on fume hoods to remind users that an
open hood costs the building “$4,500 a
year to operate and creates 70,000 lbs of
CO2 emissions.” State-of-the-art fume
hoods and new sensor technologies now
display a fume hood’s fan setting and
speed, shutdown alarm, flow rate, contaminant concentration level, and even
real-time energy use.
Figure 1. Magnets used in labs at Harvard University remind users to save energy by
closing fume hoods.
If one fume hood uses the same amount
of energy as three homes, any reduction
in the size, number or use of fume hoods
can significantly reduce energy consumption as well as the man-hours required for the EHS department to audit
and certify the hoods.
In many labs, fume hoods have become mere storage cabinets for investigators. A usage audit can identify these
areas, transition the materials to storage
cabinets, and decommission the fume
hoods. On average, an investigator uses
a fume hood approximately one hour per
day; a usage audit can identify opportunities for use of a glove box or alternative exhaust device. Some laboratories
may even be able to reduce their number
of fume hoods.
Sustainability-minded facility engineers, architects and design firms continue to question rules of thumb related
to fume hoods, even to the point of pressuring EHS departments to provide supporting evidence for their ingrained
industrial ventilation axioms. For example, if you were asked to state the required face velocity of an exhaust fume
hood, would you instinctively answer
100 fpm? If so, do you remember when
and where this number became ingrained into your IH memory?
Using the tracer gas method of meas-
uring actual contaminant containment
through ASHRAE Standard 110,2 the col-
laborative team of facility engineers and
EHS professionals at University of Cali-
fornia–Irvine reduced flow rates to 40–
70 fpm. This was based on
approximately 200 tracer gas tests,
which ultimately determined that low-
flow fume hoods performed better at re-
ducing the tracer gas concentrations
than the standard hood, even while the
sash was fully open. In addition, reduc-
ing the capture velocity from 100 fpm to
70 fpm resulted in an annual savings of
$1,500 per fume hood. Including sash
management, the total savings increased
to $2,800 per hood.
Quick! What are the required air changes
in a laboratory?
Did you instinctively answer 6 ACH?
(If you’ve worked in animal laboratories,
it’s possible your instinct was to answer
12 ACH.) Is this another ingrained CIH
rule of thumb that you aren’t willing to
back down on when engineers want to
reduce this number in their design?
OSHA 29 CFR 1910.1450
Table 1. Recommended Ventilation Rates
ASHRAE Lab Guides
This standard states that ACH is not
an appropriate concept for designing
containment control systems. The
specific room ventilation rate shall be
established by the owner.
ACGIH® 2010 TLVs® and BEIs®
The required ventilation depends on
the generation rate and toxicity of the
contaminant and not the size of the
room in which it occurs.