FAQ Group: Chemical Fume Hoods

The first step is to get a copy of the standard and determine if it applies to you. If it does apply to you, list every hazardous chemical being used or stored in your laboratory. Collect the appropriate Safety Data Sheets (SDS) / Material Safety Data Sheets (MSDS) on the chemicals. Using the guidelines in the Standard and the non-mandatory appendix, begin putting together your CHP. LTS can help with the certification of lab hoods/ventilation.

As a laboratory manager the volume of paperwork (and computerwork) is ever increasing. Between quality control, testing procedures, fiscal accountability, and a host of other demands the lab manager is wearing more hats than ever. One of the more important hats is the safety hat. OSHA has several Standards that specifically task laboratory supervisors with requirements for assuring a safe workplace. One of the most obvious standards is “Occupational Exposure to Hazardous Chemicals in Laboratories” (29CFR.1910.1450). There are also a number of substance or hazard specific standards that address occupational exposure to over thirty substances including formaldehyde (29CFR1910.1048), blood borne pathogens (29CFR1910.1030), ethylene oxide (29CFR1910.1047) and benzene (29CFR1910.1028). The Hazard Communication Standard or “right to know” standard (29CFR1910.1200) is one of the standards most frequently cited by OSHA. There is a listing of even more substances and allowable limits provided in the “Air Contaminants” standard (29CFR1910.1000). This standard establishes limits on commonly used chemicals such as acetone, ammonia, chloroform, ethyl alcohol, toluene, and xylene. Finally, lest anyone feel neglected the Section 5(a)(1) of the “Occupational Safety and Health Act of 1970” requires that “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 is the general duty clause that can be used to address any unsafe situation not specifically addressed in other regulations.

In this and successive issues of “Clearing the Air” we want to look at the listed OSHA standards and present some of the more common requirements placed on clinical and microbiological laboratories. For the complete requirements of the described standards and others that apply to your laboratory, contact your safety officer and/or appropriate regulatory authorities.

“Occupational Exposure to Hazardous Chemicals in Laboratories” (29CFR1910.1450), also called the lab standard, was designed to address the laboratory use of hazardous chemicals versus the industrial use. Laboratory use is described as where the chemical manipulations are carried out on a laboratory scale, multiple chemical procedures or chemicals are used, the procedures are not part of a production process, and protective laboratory practices and equipment are available and in common use. Laboratory scale is described as where the containers used for reactions, transfers, and other handling are designed to be easily and safely manipulated by one person.

One of the intents of the lab standard was to simplify the regulatory requirements for laboratories. The substance specific standards were typically designed to address industrial applications where larger quantities of the substances are used every day by many workers. In addition to establishing exposure limits, they describe requirements for exposure monitoring, signage, change rooms, medical surveillance, training, and other things. Some of the requirements seemed excessive for laboratories that may use a substance once or twice a month in very small quantities. Worse yet, some laboratories may use two or more of the substances regulated with substance specific standards and have to comply with multiple sets of requirements. The lab standard maintained the exposure limits set out in the substance specific standards, but provided laboratories with an alternative to the other requirements. Facilities that come under the lab standard are required to develop a chemical hygiene plan (CHP). The CHP is defined as a “written program developed and implemented by the employer which sets forth procedures, equipment, personal protective equipment and work practices” that are capable of protecting the employees from the hazardous chemicals being used in the laboratory. The CHP must protect the employees and keep the exposures below the permissible exposure limits specified in the federal regulations. The lab standard goes on to describe specific elements the CHP must address such as the standard operating procedures for working with hazardous chemicals, how the employer will determine appropriate control measures (such as personal protective equipment and hygiene practices), how the employer will assure the proper functioning of fume hoods and other protective equipment, and how are the employees informed and trained. There are other requirements for the CHP including designation of the personnel responsible to implement the plan (the chemical hygiene officer or CHO).

Although the CHP is required to be somewhat detailed, it can address many substances. Technically, a laboratory that used formaldehyde, xylene, and benzene a couple times a month in small quantities was required to demonstrate compliance to the formaldehyde standard and the benzene standard, as well as making sure that their employees were not exposed to excessive levels of xylene. The lab standard allows that lab to develop a CHP that addresses all the chemicals they work with and they only need to demonstrate that they have a good CHP and are following it.

Some laboratories may be required to meet certain substance specific standards. For example, the formaldehyde standard indicates that the standard become effective for anatomy, histology and pathology labs in it’s entirety on September 1, 1988.

With the correct hoods, usage, and testing comes the need for proper maintenance of the hoods. This includes period inspections to insure functioning sashes, exhaust blowers and exhaust alarms. Simple preventative items such as exhaust blower belt replacement can become a safety nightmare if they are overlooked. As with testing, a regular program should be documented and in place to insure that all hoods are operating and not malfunctioning. Coordinating preventative maintenance with the hood testing can allow for roof adjustments of exhaust blowers to insure proper hood airflows and sash height combinations.

Fume hoods are devices that require attention from the selection and usage process to the regular testing and maintenance procedures. A fume hood management program contains these elements and is placed under the control of the right people. The dividend yielded is maximization of worker safety and minimization of an exposure incident’s likelihood.

Even with proper selection and usage, a fume hood must be tested on a regular basis to insure that it is maximizing it safety value. The most common and inexpensive form of testing are airflow measurements. This allows an air velocity profile to be obtained for the face (front opening) of the hood and for an average airflow and flow uniformity factor to be calculated. Visual smoke tests are used to supplement the airflow measurements and show overall fume hood containment. There are two guidance documents for chemical fume hood velocities; ANSI/AIHA Z9.5- Lab Ventilation Standard and SEFA 1- Lab Fume Hoods Rec. Practices. These documents are also excellent sources for a wealth of information on lab ventilation and fume hoods and are highly recommended reading for the fume hood manager. ANSI/AIHA recommends a nominal 80-120 feet per minute (fpm) average airflow with 20% uniformity with a maximum average range of 80-150 fpm; SEFA recommends 75-125 fpm (this applies to variable air volume hoods only).

The meeting of the above criteria is a good but not absolute measure of hood containment. ASHRAE 110 is a test method that allows for direct measurement of hood containment by the release of a tracer gas in the hood. It is a more complex and expensive form of testing but yields a wealth of valuable data and allows for optimization of hood containment. An alternative to ASHRAE 110 testing is to perform chemical exposure monitoring on personnel using the fume hood to insure that no overexposures are occurring during the work procedures. While this yields less data on specific hood operation than ASHRAE 110 testing , it does complement the airflow testing and can help document the effectiveness of the fume hood(s). LTS does not provide either of these two forms of testing at the current time.

The fume hood manager should have an established testing frequency for hoods and also ensure that individuals testing the hoods are properly trained, used calibrated equipment, and have a system of quality control and review for their testing data. For these reasons, many facilities use an outside firm to test and certify their fume hoods.

Selecting the right fume hood for a laboratory is not a guarantee of improved worker safety. Users need to be trained in the proper use and operation of these hoods. It is important that the fume hood not become a chemical storage facility. The user should understand where and why the fume hood window sash should be placed. The user needs to understand how the fume hood works, how to verify basic operation, and in many cases, the procedure to be used when an airflow alarm is triggered. A competent safety, chemical hygiene, or industrial hygiene person should perform this training on a regular basis. Workers should also be observed periodically to insure that proper usage procedures are occurring and to identify areas where further guidance is necessary.

Chemical fume hoods are used in thousands of labs throughout the country to improve the safety of workers handling hazardous chemicals and reduce their level of personal exposure to these chemicals. A chemical fume hood operates on a relatively simple principle of drawing chemical vapors away from the work space within the hood and out through an exhaust system or an adsorbent filter. Despite the simple principle of operation, a fume hood management program is needed to insure their effective selection, usage, maintenance and testing. Unfortunately, this can often be overlooked by a facility and it is important to develop this type of program before fume hoods are ordered and put into active usage. As indicated above, there are several major aspects to this type of program. We will discuss testing and certification and maintenance in this edition.

One of the first steps in fume hood management is the determination of which processes need to be performed under a hood. This is typically left to the chemical hygiene officer, a safety professional, or industrial hygienist. Processes involving volatile chemicals are the most commonly identified as requiring a fume hood for safe use. Other factors of chemical use such as how often this chemical is used, how much is being used, and the actual processes the chemical is subjected to have a bearing on this decision. Chemical exposure monitoring data from personal and area monitoring and lab procedure observation can also be part of this selection process. It is important not to underestimate the chemical exposure hazard level of a procedure.

Once the need for a hood is identified, the size and type must be selected. The size of the process and chemicals should be proportional to the fume hood selected as overcrowding in the hood is not desirable. Another important consideration is the type of fume hood selected. Hoods can be defined by sash (window) type; examples are vertical, horizontal, convertible, and walk-in. Hoods can also be defined by their exhaust system; examples are ductless, constant volume, variable air volume, and auxiliary air. Airflow monitors have become a popular and almost standard option for many new fume hoods. Because of the many options available, it is important for the fume hood program manager person to work with the laboratory manager and facility ventilation engineer to select the most appropriate combination and location for each fume hood. Perchloric acid, radioactive materials, or other agents requiring special consideration place an even higher level of safety concern and additional requirements for proper hood selection.

Chemical or laboratory fume hoods are used in thousands of labs throughout the country to improve the safety of workers handling hazardous chemicals and reduce personal exposure to chemicals. The Scientific Equipment & Furniture Association defines a laboratory fume hood in part as “a ventilated, enclosed work space intended to capture, contain, and exhaust fumes, vapors and particulate matter generated inside the enclosure.” A chemical fume hood operates on the relatively simple principle of drawing chemical vapors, fumes, etc. away from the work space within the hood and out through an exhaust system. A fume hood management program is needed to insure the effective performance of fume hoods. This program should address the selection, usage, maintenance and testing of the fume hoods. The need to systematically monitor and maintain the performance of fume hoods can often be overlooked. There are several major aspects to this type of program.