Pressure Control in BSL-3 Laboratories
Adam R. Bare, PE, Newcomb &
Body
For reliable and constant containment in BSL-3 laboratories, HVAC
and laboratory controls systems must be designed to ensure that
pressure relationships are continuously maintained. The term "relationship"
is key to this issue because the magnitude of the differential pressure
is irrelevant in a BSL-3 environment. The intent is to ensure that
airflow is always traveling in the correct direction (given the
premise that contaminants are not capable of traveling upstream).
In the past, designers of BSL-3 facilities have used differential
pressures on the order of 0.05" wg, or even as high as 0.1"
wg or more. This presentation will offer real world examples of
what those differential pressures equate to, as well as explain
that differential pressures of those magnitudes were applicable
to controls systems of the past. They are no longer necessary. Much
lower differential pressures, in the range of 0.005"-0.01"
wg, are more applicable when using today's faster, more accurate
controls devices.
Another concern is the level to which the systems are automated
because the more systems need to sense and respond, the faster,
more reliable, and smarter the controls systems need to be. This
presentation will go on to explain actual applications of those
controls in a BSL-3 facility, and provide a simplistic approach
to configuring the HVAC and controls systems so as to ensure that
pressure relationships are maintained regardless of what is happening
either inside or outside of the building (such as doors opening
or closing, strong winds blowing against exterior walls, etc.)
Labs21 Connection:
Designers of BSL-3 facilities are concerned about using lower
differential pressures because any breach in containment has direct
implications on life safety. BSL-3 laboratories are typically designed
to have a series of cascading pressures from more-to-less contaminated
areas. With cascading pressures starting at zero and incrementally
increasing as one approaches the entry areas, the static pressures
in the entry areas can be quite high. The higher differentials can
yield over-pressurization of front entry areas, air turbulence,
eddy currents, and nuisance issues. Therefore, differential pressures
should be maintained at the lowest possible magnitude that can be
reliably controlled. Not only does this create a more comfortable
and usable environment, but the reduction in pressure also allows
the amount of exhaust to be reduced. Lowering the exhaust lowers
the outside air requirements. The HVAC systems will get smaller
and use less energy—a fundamental aspect of the Labs21 Approach.
Using constant air volume systems in containment areas and variable
air volume systems in entryways and corridors is a simplistic approach
to configuring lab systems geared towards minimizing the amount
of automation. The primary goal is to reliably control containment
throughout the life of the facility. Contrary to typical laboratory
design, this approach does not require complicated and expensive
airflow controls systems, leaving the owner with a facility that
reliably sustains its pressure profile.
Biography:
Adam Bare earned his bachelor of mechanical engineering
degree from the Georgia Institute of Technology in 1997 and an MBA
from Georgia State University in 2001. During his eight years with
Newcomb & Boyd, he has developed a particular expertise in the
design of mechanical systems for laboratory and research facilities.
Mr. Bare's experience includes laboratory projects for Georgia Public
Health, East Carolina University, University of Alabama, and the
Medical University of South Carolina. His work totals more than
one million square feet and over $175 million in construction value.
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