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Room Pressurization Criteria, Effectiveness, and Energy Conservation in Controlled Environments

Jim Coogan, Siemens Building Technology

Pressurization is one of the most important considerations in the design of a controlled or critical environment (CCE) such as a general lab, biosafety lab, cleanroom, hospital isolation room, or even a smoke control space. Pressurization technology utilized in a CCE space normally is intended to direct desired flow patterns and prevent airborne cross contamination.

Pressurization design has been traditionally based on intuitive suggestion instead of well-validated guidelines. Due to unknown room conditions during design phases, design engineers tend to over design pressurization systems to prevent possible problems during air balancing and commissioning. This mentality and practice could cause adversary effects and significant energy wastes. Improper pressurization/depressurization can cause undesired airflow strengths and patterns, uncorrectable airflow directions during balancing and commissioning, which can result in contaminated products, ineffective protection for working environment, endangering operation personnel's safety, as well as increased energy costs.

This presentation will provide a systematic analysis on pressurization criteria, primary and secondary barriers, suite (multiple rooms) and staged pressurizations, decontamination effectiveness, simulation aid, automatic room air-tightness test, updated adaptive control strategies, recommended practices on energy conservation, and quantification between the reduction of pressure differential level and the possible energy saving.

The presentation will further offer the recommended practices on energy conservation of pressurization systems, such as reduction of room enclosure leakage, utilization of barrier devices to lower the required room pressure levels, utilization of VAV supply and exhaust systems to lower total air consumption, lowering air volumes during unoccupied modes while maintaining required pressurizations, locating CCE spaces in interior zones to enhance the stability of room environmental conditions and reduce cooling/heating loads, utilization of network flow simulation to enhance and validate pressurization effectiveness, low-pressure-drop design for ductwork, airflow control devices and other components, and etc.

Labs21 Connection:

Energy conservation on room pressure control for laboratories is an important issue but has not been particularly addressed by design professionals. Due to complexity and many unknown factors during pressurization design, design engineers tend to place low priority on energy conservation and over design pressurization systems, which could cause unnecessary energy wastes.

This presentation will discuss decontamination effectiveness and simulation tools to emphasize on occupant safety, will quantify possible energy saving on reduction of pressure differential level to further analyze whole building efficiency on a life-cycle basis, and will list the recommended practices to promote energy efficiency efforts and employ a range of energy efficiency strategies by design professionals. These are the key elements of Labs21's approaches.


Jim Coogan, P.E., is a Senior Principal in product development and applications for Siemens Building Technologies. He has 25 years experience designing microprocessor-based controls for mechanical systems, with 15 of those spent in the HVAC industry. Jim has served as chairman of ASHRAE Technical Committee 1.4 Controls and has been an active member of TC 9.8 Laboratory Systems. Publications include technical papers on room pressurization and laboratory system commissioning. He has participated in development of HVAC control products ranging from simple room controllers to Internet-based operator interfaces. Jim earned his S.B. in mechanical engineering at MIT in 1980.

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