Laboratory Air Changes Per Hour: Why All the Hot Air?

Lou DiBerardinis, MIT

The issue of selecting the proper air changes per hour for laboratories has been a perplexing and sometimes confrontational one. Architects, engineers, EHS professionals, and users may have different perspectives on what this really means and sometimes are frustrated by the difficulty in discussing and grasping the real issues. This presentation is not designed to recommend a specific air exchange rate but rather discuss the process that should be followed when selecting a rate and the factors that need to be considered. Some guidance will be provided on how best to weight the factors and what some consequences and benefits will be realized by some decisions.

During the past decade the trend in laboratory design has been towards reducing the volume of air exhausted from laboratories through general exhaust or local exhaust hoods. The purpose has been to reduce energy use while not compromising the health and safety of laboratory workers. Early guidelines called for air exchange rates between 10-15 air changes per hour mostly based on heating and cooling needs. As the design of laboratory fume hoods and general ventilation improved and better work practices were employed, the air exchange rate was allowed to be lowered. Experience to date has not resulted in any reported adverse health effects where proper practices and maintenance were followed. However, EHS professionals are still cautious because adverse health effects may be difficult to measure and relate to a specific exposure and also take many years to manifest. While there have been limited exposure assessment studies performed in the laboratory, several recent studies have provided some reassuring information. In addition, EHS professionals are concerned that decreasing air exchange rates may degrade laboratory air quality similar to the way IAQ problems occurred in office areas due to reduced outside air exchange rates. Although the EHS issues associated with lower air exchange rates are not well understood, a model for a decision logic that can be used in the design process will be presented.

This presentation will include a review of current regulations and guidelines on air changes per hour in laboratories, a review of the literature describing studies directed at the air exchange issue including exposure assessments and a design process and decision logic that can be used to help all the stakeholders involved better understand the questions that need to be addressed and the consequences and benefits of decisions made.

Biographies:

Lou DiBerardinis CIH, CSP, received his Bachelor of Science Degree in Chemical Engineering from Northeastern University in 1970 and a Master of Science Degree in Industrial Hygiene from Harvard University in 1975. He is a Certified Industrial Hygienist and a Certified Safety Professional.

Mr. DiBerardinis has been affiliated with MIT since 1989 and assumed the position of Director, Environment, Health and Safety in 2001. Mr. DiBerardinis was an Industrial Hygiene Engineer for Polaroid Corporation from 1986-1989. He joined Harvard University in 1970 as part of a research group at the School of Public Health and from 1976 to 1986.

Mr. DiBerardinis is a visiting lecturer at Harvard University School of Public Health where he teaches in several graduate courses and continuing education programs. He is the author of numerous technical publications and co-authored the text "Guidelines for Laboratory Design: Health and Safety Considerations" and is editor of the "Handbook of Occupational Safety and Health," both published by John Wiley and Sons. He has served as chair of the American National Standards Institute Z9.5 subcommittee on Laboratory Ventilation since 1984.

Mr. DiBerardinis maintains professional affiliations with the American Academy of Industrial Hygiene (president 1991-1992, secretary/treasurer 1983-1986), AIHA, the British Occupational Hygiene Society, American Society of Heating, Refrigerating and Air Conditioning Engineers, American Conference of Governmental Industrial Hygienists and ASSE.

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