Tuesday, 28 June 2016: 8:00 AM-9:30 AM
Fundamentals and Applications
Chair:
Kishor Khankari, Ph.D., AnSight LLC
Technical Committee: 09.11 Clean Spaces
Sponsor: 9.6
CoSponsor: 09.10 Laboratory Systems
Air Change Rates (ACR) are often specified in standards, codes and design guidelines as supply airflow requirements for healthcare, cleanrooms, laboratories and other similar facilities. This legacy practice has been implemented for several decades. With increased awareness of energy efficiency and cost of HVAC operations it is essential now to review this philosophy. This seminar provides historical perspective; current practices and recommendations; and pros and cons of ACR philosophy in the three major industry sectors. In addition the importance of supply airflow path and the distribution of the supply air on effectiveness of contaminant removal will also be presented.
1 ACR Philosophy and Practice: Health-Care Facilities
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Travis R. English, P.E., Kaiser Permanente |
Health care facilities are the only spaces where an ASHRAE-authored standard uses air changes exclusively. This presentation looks at the origins of health care ACRs, their intents, and changes over time. It discusses the outcomes addressed by those ACRs, and how those same outcomes could be addressed using alternate methodologies. It also looks at some of the leading health care air quality management strategies used abroad, and how those could be adopted domestically.
2 ACR Philosophy and Practice: Laboratory Systems
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Thomas Smith, Exposure Control Technologies, Inc. |
People working in laboratories rely on proper operation of laboratory hoods and ventilation systems to prevent over exposure to hazardous airborne contaminants generated during scientific procedures. Lab safety can depend on the quantity and distribution of airflow. The OSHA Laboratory Standard 29 CFR 1910.1450 and other relevant standards recommend between 4 air changes per hour (ACH) and 12 ACH of one pass air. There is little guidance on correlating risk with ACH and assessing the effectiveness of contaminant dilution and removal. This paper explores specification of ACH for labs and the impact on lab safety and energy efficiency.
3 ACR Philosophy and Practice: Cleanrooms
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Philip Naughton, Applied Materials Inc |
Cleanrooms typically rely upon air change rates to help maintain a given cleanliness class. Air change rates can vary between 2 ACH to well over 500 ACH. There is much anecdotal data supporting a correlation between cleanroom cleanliness and the air change rates with little empirical data. Many cleanroom owners are compelled by regulating authorities to maintain high air change rates. This presentation reviews the current regulatory guidance for cleanroom air change rates as well as present data on cleanrooms that have been able to reduce their air change rates and still maintain their required cleanliness.
4 Analysis of Airflow Paths and Contaminant Removal Effectiveness
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Kishor Khankari, Ph.D., AnSight LLC |
Air Change Rates are often specified assuming well mixed conditions in the spaces to achieve overall dilution of contaminants. Actual distribution of contaminants in the space are seldom uniform and depends on several factors including the locations of air supply and returns, strengths and location of contaminant sources, and strength and locations of heat sources. The flow path of contaminants in the space play important role in determining the concentration levels and overall effectiveness of contaminant removal. This presentation demonstrates how airflow paths affect the effectiveness of contaminant removal in patient rooms, cleanrooms, and laboratories.