Basic Documentation

Ventilation Systems
Siemens Industry, Inc. 107
Topic Requirement(s) Commentary
Room and
Duct
Pressurization
(Continued)
ASHRAE, 2011 Handbook - HVAC Applications, Laboratories, Pg. 16.12 Room
Pressure Control:
Because maintaining an airtight seal is rarely practical, the air pressure in the
laboratory must be maintained slightly negative with respect to adjoining areas.
Exceptions are sterile facilities or clean spaces that may need to be maintained at
a positive pressure with respect to adjoining spaces.
American Institute of Architects, GUIDELINES FOR PLANNING AND DESIGN
OF BIOMEDICAL RESEARCH LABORATORY FACILITIES 1999
C.7.5.f. Laboratories containing harmful substances shall be designed and field
balanced so that air flows into the laboratory from adjacent (clean) spaces, offices
and corridors. Air supplied to the corridor and adjacent clean spaces must be
exhausted through the laboratory to attain effective negative pressurization.
C.7.7.a Laboratories in general should remain at a negative pressure in relation to
the corridor and other non-laboratory spaces. Laboratory air shall flow from low-
hazard to high-hazard use areas. Administrative areas in laboratory buildings must
always be positive with respect to corridors and laboratories. The entire building
shall be maintained at an air pressure above atmospheric to reduce or eliminate
unwanted, unfiltered air and water infiltration.
C.7.7.b Corridor supply air distribution shall be sized to offset transfer air to
laboratories while maintaining an overall positive building pressure. Loading and
receiving docks must be maintained as positive to prevent to prevent the entrance
of vehicle fumes.
Institute of Laboratory Animal Research, Commission on Life Sciences,
National Research Council, Guide for the Care and Use of Laboratory Animals,
Eight Edition, 2011:
Page 139: Pressurization assists in controlling airborne contamination and odors
by providing directional airflow between spaces. Areas for quarantine, housing and
use of animals exposed to hazardous materials, and housing of nonhuman
primates should be kept under relative negative pressure, whereas areas for
surgery or clean equipment storage should be kept under relative positive
pressure with clean air.
The preferred method of preventing cross
contamination is by tightly sealed walls and
floors and by not allowing recirculation of
contaminated exhaust air. However,
maintaining proper room pressure
differentials adds another level of protection
and is necessary to enable persons to pass
from one area to another (that is, via
doorways, etc.)
Human
Occupancy,
Room
Temperature
and Humidity
ASHRAE, 2011 Handbook - HVAC Applications, Health Care Facilities, Pg. 7.6
DESIGN CONSIDERATIONS:
Ambient design conditions for humans in a laboratory room setting (From Table 3
of the handbook):
74 +/- 2
o
F and at 30 - 60% RH
Uncomfortable lab conditions may prompt
the occupants to use portable fans, heaters,
block supply diffusers and use other means
that can cause unsafe conditions. Certain
biological labs may require specific ambient
conditions based on the biological agents
present.