ASHRAE Journal - January 2015 - 22

TECHNICAL FEATURE

Most codes mention measurement of: CO, VOC and
CO2. CO is normally a by-product of the combustion
process and is likely not significant in lab spaces.
VOCs are often, but not always, a result of out-gassing
of chemicals in furniture and building materials. The
concentration of VOCs can be minimized by flushing
the building space prior to occupancy. CO2 is a good
guide of human activity.
Maintenance of a fume hood often follows the
original methods used to certify the hood on a preset schedule (i.e., yearly or semiannually). But good
contaminant control should really be based on the
continuous usage of the hood not on an arbitrary
time schedule. As noted above, one way to measure
the safety of the hood might be locating sensors (both
velocity and contaminate) on the sill of the hood and
wirelessly transmitting the measurement data to
the room controllers, which could be used for point
location for demand ventilation. The added cost of
this kind of contaminant measurement and control
is minor when compared to the cost of normal safety
devices.
Most of these sensor designs are based on proven
technologies. Examples of these technologies include
electrochemical (metal oxide conductor on an
alumina substrate with a heater), non-dispersive
infrared (NDIR) and solid state. There are others. Electrochemical-based sensors are commonly
designed to detect oxidizing gases (CO, H2S, SO2,
and NO) as well as reducing gases (O3 and NO2).15,16
NDIR sensors are usually used to measure CO2
concentration.
Most technologies will sense in the range of several
ppm although they should be field calibrated and then
periodically monitored for aging. Many sensor technologies are reviewed by Ho, Robinson, Miller and Davis.17
Often, these sensors are a single point and do not
sample different locations in the space. Dead air (poor
mixing) and point discharge will affect the accuracy of
the IAQ space readings. I suspect as the cost of sensors
continue to drops, a series of sensor packages may be
located in the perimeter (walls) of the space to report
the total space IAQ to the space controller. A sensor
package mounted in the supply air measuring the contamination within the supply air can provide a reference source for the amount of contamination permitted in the space.
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ASHRAE JOURNAL

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JAN UARY 2015

Conclusions
I suggest that using Standard 62.1 can provide for
excellent laboratory IAQ and result in significant
energy savings. Standard 62.1 can be a good baseline
for the energy consumption of individual lab spaces
as well as the entire building. An additional advantage is that these methods are not expensive and can
be applied to existing as well as new laboratories. Of
course, maintaining control over the space contaminants should be the primary goal of the laboratory
environment but other guidelines, i.e., Standard 62.1
can be equally as valuable in the occupied spaces of a
research laboratory.

In the Future
It's likely that the range of the sensors will increase
and the cost of sensors will continue to fall, so packages of sensors can be installed at various locations
within the space and possibly within the air-handling
unit. Sensor technology will continue to expand (i.e.,
nanoelectrode technology is currently used for biomedical and water sensing and may possibly become
suitable for air/contaminate measurement and sensing). I anticipate that these "stand-alone" sensor packages will transmit information wirelessly to a local
space controller and then to the building management
system.
It's likely that design software packages will include
space mixing calculations that will determine the
location of supply and exhaust devices. I anticipate
that sensors will be located on the face of the fume
hood that will maintain clean indoor air next to the
hood users, and that the IAQ values and the energy
consumption of each space will be displayed so
the occupants will have some energy consumption
feedback.
Nano-textured aluminum tube surfaces can transfer almost four times the sensible heat as untextured
aluminum tube surfaces.18 The heat transfer of the
entire assembly will not show this kind of an increase.
This advancement will transfer quite a bit of additional
energy from the exhaust stream and also act as a physical barrier to any potential cross contamination. These
results are in the experimental stage but indicative of
some future products.
Other innovative designs for laboratories can be
found with a good Internet literature search.19

ASHRAE Journal - January 2015

Table of Contents for the Digital Edition of ASHRAE Journal - January 2015