configuration, delay times up to the
maximum allowed 15 minutes are
possible. The PID used in the system
uses a 10.6 eV bulb. Flammable gases
or vapors with a higher ionization
potential—for example, hydrogen—are
invisible to the system.
A laboratory operations permit
system should set threshold limits to
the use of oxygen depleting agents.
For example the hazards from spillage,
dispensing or use of liquid nitrogen
have to be considered.
ENERGY SAVINGS EVALUATION
The optimization system used at
NU reduces the general laboratory
exhaust and respective fresh air inflow,
but it does not regulate fume hood
Each system uses a “sensor suite” that accepts a variety of sensors for multipoint sampling. The sensor suite
analyzes each air packet and sends smart signals to optimize ventilation. Image: Aircuity Inc.
number of fume hoods demands high
exhaust ventilation will not realize
energy savings. In equipment rooms
where the equipment heat loads demand
high ventilation rates for cooling, there
is nothing to gain from the system.
However, future laboratory equipment
design conversion from air to liquid
heat exchange may lead to additional
energy saving opportunities in these
Chemistry teaching labs have a
large number of fume hoods, but only
limited daily or periodic use. At other
times the fume hoods may be empty.
Best design practice may be to manually
turn all fume hoods exhaust on/off
using a master switch. Investment in an
optimization system may have limited
payback in these areas, but could
provide lab monitoring capabilities.
Since the system’s particulate sensor
only monitors two particle size bins,
it usually is not used to dynamically
control ISO Class 1 to ISO Class 6
cleanroom ventilation rates. Currently,
NU is investigating the use of the
particle sensing technology for ISO
Class 7 to ISO Class 9 clean areas.
The best payback may be achieved in
vivarium animal spaces. Animal releases
of VOC and particulate into the secondary
barrier (the room) will dynamically open
ventilation valves for more fresh air. With
directly ventilated cage racks this release
is not frequent. We expect significant
energy savings when the ventilation rate
can be kept well below the traditional 15
air change design for vivaria.
Efforts to accurately quantify NU total
laboratory energy savings are continuing.
In addition, NU uses the data delivered
through these ventilation optimization
systems to diagnose air quality or
temperature-related issues that may arise
during laboratory operation.
Markus Schaufele, MS, CSP, is
Manager of Standards, Compliance and
Emergency Planning, Office for Research
Safety, Northwestern University. https://