Chemical Fume Hoods

Chemical fume hoods provide an extraordinary function. The ability to safely, conveniently and, at close proximity, work with materials that, otherwise, may be harmful or fatal. Without laboratory fume hoods many of today's discoveries and conveniences may not exist.

Fume hoods must function properly to deliver the protection promised. At minimum, every fume hood must be tested annually. The steps required to ensure safe operation are not difficult, should not be ignored, and are critical to good chemical hygiene.

Our firm was recently asked to validate the performance of twenty two freshly installed chemical fume hoods. In reviewing the provided specification it became clear that the information was dated and incorrect. This lack of understanding chemical fume hood standards, performance and requirements is common.

Codes, standards and regulations are no longer prescriptive - they are performance based. The goal is safety, not a specific face velocity. For example, current standards do not state that a fume hood must meet a specific measured flow rate (100fpm), rather the hood must provide a safe working environment for personnel. The owner is responsible for determining the measured safety parameters.

Following is a brief history of chemical fume hood standards. This is not an exhaustive study, simply a snapshot of relevant documents. For more information we recommend reading current versions of the referenced documents. You may also call our office for help:


The Scientific Apparatus Manufacturers Association (SAMA)

SAMA no longer exists. Standards published by SAMA, which included LF7-1975 and LF10-1981, classified chemical hoods as follows:

  • Grade A - for use with extreme toxicity – face velocities 125- 150 fpm
  • Grade B - for most operations – face velocity of 100 fpm
  • Grade C - for low hazard – face velocities of 75 - 80 fpm

SAMA standards are more than 40 years old and relied exclusively on face velocity as the performance benchmark. SAMA is only interesting as a historical reference.

1980 – Present

The Scientific Equipment Manufacturers Association (SEFA)

 SEFA has published a variety of great publications, all of which are available on-line. The most recent fume hood standard was published in 2010 (SEFA 1 – 2010). This standard in many ways mirrors the approach of the Laboratory Ventilation Standard (ANSI/AIHA Z9.5).

Hoods (chemical, biological, glove boxes, etc.) must be routinely evaluated to determine if they are functioning  properly. At minimum, evaluations should include individual performance  surveys (tracer gas testing, documentation  of qualitative measures, continuous monitoring devices, etc.) and, if required, a plan for corrective action. A qualified individual must be designated to oversee the evaluations, report the results and correct any performance shortcomings.

1990’s FORWARD

OSHA 1910.1450: Occupational exposure to hazardous chemicals in laboratories

The OSHA Lab Standard was first published in 1991 and sets specific safety standards for laboratories. Additionally, OSHA’s General Duty Clause states:

“Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees”

This law is available on-line free of charge on line. A page from OSHA's website with noted requirements can be found here.

ANSI/AIHA Z9.5- Standard for Laboratory Ventilation

The American Industrial Hygiene Association (AIHA) first published this standard in 1992.This was a good first effort; however, it was a mix of information that was not always clear.

The 1992 Version helped specify hood selection based upon the ANSI-ASHRAE 110 method, required alarm systems for new and re-modeled fume hoods and recognized the importance of proper supply air distribution as critical to proper hood function.

The 2003 Version was a better effort and, for the first time, required Fume Hoods to be evaluated on-site via the ASHRAE 110 – (most recent version) method.

It was one of the first published  documents to recognize that chemical hoods do not exist in a vacuum and that testing conducted by the manufacturer may not match results in your lab.  In fact, empirical studies cited in this standard found hood failure rates of 17% for hoods with “correct” face velocities.

Critical concepts of the 2003 revision include:

Chemical fume hoods are mechanical devices and a component of the mechanical system servicing the laboratory  and many factors impact performance.

All new and remodeled  chemical hoods shall be tested via the ASHRAE 110 method on site As Installed (AI) when new or As Used (AU) for hoods currently in use.

All new hoods shall be commissioned-guidance provided.

The ANSI Z9.5 Laboratory Ventilation has been updated and the public review period has passed. It is anticipated that this third revision will be published in the fall of 2012.

 A quick highlight of the new requirements as it applies to Chemical Fume Hood Testing is as follows:

 Where the design sash opening area is less than the maximum sash opening area, the hood shall be equipped with a mechanical sash stop.

Minimum Flow Rates: “… laboratory hoods shall maintain a minimum exhaust volume to ensure that contaminants are properly diluted and exhausted from a hood.” A list of factors to consider when setting the minimum flow rate is included.

 Ductless Fume Hoods – “A Hazard Evaluation and Analysis shall be conducted as directed in ANSI/AIHA Z9.7 and Section”. Ductless fume hoods have limited application.

The face velocity test method has been clearly defined.

ASHRAE 110 Pass / Fail has been clearly defined.

A procedure for measuring Cross Drafts is included.

 LabTech Midwest has anticipated this publication for the past several years. The new document in draft form is a huge step forward in Laboratory Ventilation design, maintenance and testing. As with every new publication our test procedures will be updated with the new requirements as soon as this document is published.


The ANSI/ASHRAE 110-1995 Method of Testing Performance  of Laboratory Fume Hoods is a test methodology, not a performance specification. Prior to the publication of ANSI Z9.5 - 2003 this test was employed exclusively as a test-design protocol. The Z9.5 - 2003 revision mandated the ASHRAE method procedure for all new and remodeled  hoods. If your testing agency is not equipped to perform this test your firm should seek a qualified testing partner to establish a performance based certification approach.

ASHRAE Method - 1995: Method of Testing Performance of Laboratory Fume Hoods

First published in 1985 and last updated in 1995 this is a specific test procedure. All hoods should be tested once (at minimum) to establish a baseline performance specification. It may be impractical to use the ASHRAE 110 method as an annual test, so in future years a “less rigorous” test can be employed per ANSI Z9.5. This method:

Outlines qualitative and quantitative means of testing fume hoods.

 Provides a specific face velocity measurement  method

Provides measurement of dynamic challenges  such as sash movement  effect, VAV response testing, room pressurization, etc.

Pre-Purchase Performance Test - US Environmental Protection Agency (USEPA)

Published by the US-EPA on April 26, 2006, the Procedure for Certifying  Laboratory Fume Hoods to Meet EPA Standards is a specific testing approach, not a performance specification. As a pre-purchase protocol it is a selection tool. Prior to purchasing any fume hood a review of the EPA test results is prudent. Your hood vendor should provide test results upon request.

LTMW 0113 - Test Procedure

Updated annually, this test method is the “less rigorous” test referenced in ANSI Z9.5 once an ASHRAE 110 baseline has been established. At minimum, this test should be conducted annually for each hood according to ANSI Z9.5.