Reducing Laboratory Fume Hood Minimum Exhaust Rates: A Case Study of How University of California, Irvine Safely Implemented Exhaust Flow Rate Reductions in its Laboratory Fume Hoods.

David Kang, University of California, Irvine
Thomas Smith, Exposure Control Technologies, Inc.

The 2012 ANSI/AIHA Z9.5 'Laboratory Ventilation' standard recommends new minimum fume hood flow guidelines that are based on the internal volume of the fume hood and internal air changes per hour (ACH). Instead of specifying that a minimum flow of 25 cfm/ft2 be maintained, the new ANSI/AIHA Z9.5 now states that 'laboratory fume hoods shall maintain a minimum exhaust volume to ensure that contaminants are properly diluted and exhausted from a hood', where a range of 375 ACH to 150 ACH is proposed as adequate. An internal air change rate of 375 is roughly equivalent to 25 cfm/ft2 and 150 ACH corresponds to roughly 10 cfm/ft2. The ANSI Z9.5 standard requires users to consider the following when selecting an appropriate minimum air change rate and minimum fume hood flow:

a. Control of ignition sources within hood

b. Design of hood (materials, etc)

c. Maximum chemical generation rates in hood

d. Potential for increased hood corrosion due to decreased flow

e. Effect of reduction on exhaust stack discharge velocity

f. Fume hood density

g. Need to affect directional air flow

h. Operating range of fume hood

Reducing the minimum flow from 375 ACH to 150 ACH through fume hoods in the closed sash position where appropriate would reduce annualized flow and yield significant reductions in energy and operating costs for a laboratory. In 2012, as part of its Strategic Energy and Smart Labs programs, UC, Irvine investigated the feasibility of reducing the minimum fume hood flow below 25 cfm/ft2 by performing tests on several hoods around campus to develop criteria for safely reducing exhaust flow rates when the sashes were closed. This discussion will present some of the results of implementing these flow reductions and how they translated into energy and operating cost savings and carbon footprint reductions.

Biography:

David is an industrial hygienist with the University of California, Irvine and currently serves as the Environmental Health and Safety project leader for energy related projects impacting ventilation on campus.

Thomas C. Smith is the President of Exposure Control Technologies, Inc. (ECT, 231-C East Johnson St, Cary, NC 27513; 919-319-4290, tcsmith@labhoodpro.com). Mr. Smith is a leader in safety and energy management for research facilities. He specializes in helping laboratories provide safe, dependable and energy efficient operation of laboratory hoods and ventilation systems. He holds a BS degree in Mechanical Engineering from North Carolina State University and a MS degree in Environmental Engineering (Industrial Hygiene) from the University of North Carolina. Mr. Smith is active in developing national and international standards for lab ventilation and serves as Chair of the ANSI/AIHA Z9 Standards for Ventilation and Health, Vice Chair of ANSI/ASHRAE 110 Fume Hood Testing and past Chair of ASHRAE TC9.10 Laboratory Systems. Since 1985, Mr. Smith has participated in hundreds of laboratory ventilation projects and evaluated thousands of laboratory hood systems. His work has improved the safety of lab environments, reduced energy consumption and saved millions of dollars in operating costs for facilities throughout North America.

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