What does LTS do with the parts or filters that are replaced?


All used parts and filters belong to the customer and will be left at your facility for disposal. Filters will be put into the box from the new filters and a “Decontaminated” label will be placed on the box. As every facility has its own policy on disposal of these components, please follow your facility’s policy and procedures.



In some BSC work, radioisotopes solutions are used. These solutions could give off radioactive vapors which would pose a Beta and even Gamma radiation hazard. Since a HEPA filter will not stop vapors, it is expected that the radiation will leave the BSC and exit the building. Prior to accessing and changing a HEPA filter, it is good practice to have a health physicist assess and document that the BSC is free of radiation hazards or to supervise any safety measures required by a radiation hazard if it exists. The HEPA filter itself would be decontaminated as biological and/or chemical waste (see the other sections), prior to removal and be disposed of a non-hazardous waste unless otherwise regulated. If the HEPA filters did contain radioactive waste, the health physicist would advise on proper disposal procedures.



HEPA filters used in BSCs for chemo (antineoplastic) drug preparation pose a chemical hazard as opposed to a biological hazard. Typically, BSCs are used for either biohazard or chemo drug work therefore mixing of these two types of hazards are rare. Chemo drugs can pose a variety of acute and chronic occupational exposure hazards. The current guideline document is published by OSHA: in Chapter 21 of their technical manual. When a HEPA filter is changed in a BSC used for chemo drugs, the old filter is classified as hazardous drug (HD) waste. It should be bagged in plastic, labeled, and disposed of as solid hazardous drug waste. Disposal of HD waste can be regulated by the EPA, state, and local toxic waste laws depending on the drugs used. It is important that the facility have in place a hazardous drug safety and health plan which would document how HD waste should be disposed.



HEPA filters in BSCs used for biohazard work are viewed as contaminated with whatever biological agents used in the BSC. The OSHA Bloodborne Pathogen Standard states equipment which may be contaminated with blood or other potentially infectious materials….shall be decontaminated as necessary. This procedure is detailed in NSF International Standard 49 Informative Annex 2. Most HEPA filters that have been decontaminated are viewed as non-hazardous and are disposed of as non-regulated waste. Some biological agents are resistant to gaseous decontamination and may need special handling. In some states or localities there may be regulations that prohibit non-regulated disposal of any perceived medical waste. So even if a HEPA filter is decontaminated, the HEPA may still be incinerated or packaged as medical waste.

How do I dispose of a used HEPA filter?


High Efficiency Particulate Air (HEPA) filters are used in biological safety cabinets (BSCs), laminar air flow clean workstations, and other air handling equipment to provide clean work environments. In the case of BSCs they also provide worker and environmental protection by removing contaminants from the air. When a HEPA filter is changed, the proper disposal of the used HEPA is always a concern. HEPA filters from laminar air flow workstations and other product protection applications may only filter room air therefore filters may contain only the normal particulates found in air. These filters are typically not viewed as being contaminated and can be disposed of as non-regulated waste.

Can we work in the lab during a decontamination?

Before we begin to decontaminate a cabinet, the LTS technician will review the procedure with you and post warning signs on the cabinet and entrances to the lab where the decontamination will be performed.

While it may be safe to be in the lab during decontamination, we recommend that you do not stay in the lab during the decontamination process. An LTS technician will let you know when the process is complete.

When is decontamination required?


Decontamination is required when maintenance work, filter changes and performance tests require access to any contaminated portion of the cabinet. Decontamination may be desirable prior to certification testing when the cabinet has been used with certain BSL-2 agents and recommended when it has been used with any BSL-3 agent. Decontamination should also be performed prior to relocation of the biosafety cabinet in case a contaminated plenum is breached during its relocation.

What is a “decontamination”?


A microbiological decontamination is a two step process that involves both a space decontamination (surface disinfection) and a gaseous decontamination (Paraformaldehyde/Chlorine Dioxide). LTS works with the cabinet user as a team to accomplish this process. Typically the user performs the first step that is surface disinfection and then LTS performs the second step that is gaseous decontamination. Gaseous decontamination is a process of using paraformaldehyde/chlorine dioxide gas contained in a cabinet for a set amount of time to remove all contaminates. An industry standard decontamination procedure can be found in NSF/ANSI 49 Informative Annex 2. CETA CAG-004 Biological Decontamination and Disinfection of Accessible Surfaces in Biosafety Cabinets is another document to help understand the process in its entirety.

So how do we start complying with the lab standard?


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.

What safety programs is a lab supervisor required have?


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.

Testing and Certification


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.

Fume Hood Selection


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.

What makes an effective chemical fume hood management program?


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.

Does your hood really need to be ducted?


Many biological safety cabinets and chemo hoods used in hospitals today are ducted to the outside. This is the only way to protect the user from many non-particulate hazards like chemical fumes.

Venting of the unit’s exhaust to outside the building can make solving airflow problems a lot harder for you. A ducted hood with a problem involves people from different areas of the facility. It’s like a computer problem, with the hardware people blaming the software people, the software people blaming the hardware, and you stuck in the middle.

If your hood won’t come on because of insufficient exhaust or your certifier can’t certify it because the exhaust is too low, the hardest battle can be getting everyone to understand. The certifier says it’s too low, the facilities person says it’s more than enough and you just want to get your hood certified. Controlled Environment Testing Association (CETA) has 2 application guides that will provide helpful hints on understanding and dealing with these and other kinds of problems.

  • CAG-007: Exhaust System Requirements of Class II Biosafety Cabinets
  • CAG-010: Application Guide for Informational Notes to Meet the NSF/ANSI 49:2010a Standard Requirements

LTS can provide a copy of these 2 documents upon request.

There are three types of Biological Safety Cabinets. A Class I is basically a fume hood with a filter. You can’t use large amounts of chemicals in a Class I because they can eat through the filter. Class I cabinets are great for personal protection, but offer no product protection. A Class III cabinet is a ventilated glovebox. Air is filtered in and out and you use gloves mounted in glove ports to work with materials inside the hood.

The five types of Class II cabinets, A1, A2, B1, B2, and C1 are what most of us refer to when we think of a chemo hood or biohood. You reach in through an 8 or 10 high opening below a window. Air is drawn into the hood through that opening like a fume hood. Unlike a Class I cabinet, filtered air is also blown onto the work area from above, so your product is protected from outside contaminates. (Another similar type of equipment is a laminar air flow workstation which blows filtered air over the work space. Since you get product protection but no personnel protection, this isn’t considered a safety cabinet.)

Not all Class II cabinets need to be connected to your building’s exhaust. The Class II types A1 and A2 cabinets do not have to be connected to an exhaust duct to function properly. However, if they are connected to an external exhaust they must be canopy(thimble) connected. The other three types – B1 (sometimes called an NCI hood after the National Cancer Institute), B2 (commonly called a Total Exhaust hood), and the newest C1 all need to be connected to an external exhaust system to function.

If you have the A1 or A2 type, it may be possible to solve your exhaust problem by allowing the unit to vent to the room. If you are dealing with only particulate hazards, the cabinet’s filters should be able to capture the hazard. If those particulates might offgas or if you are using non-particulate hazards like low amounts of ether or other gases, the cabinet’s exhaust may need to be ducted outside. Your facility’s safety officer can help determine this with you.

As a customer, what do I need to do to prepare for a BSC certification?


Before our technician can begin to test your cabinet, all removable nonessential to cabinet operation (acceptable option components) need to be removed from the cabinet. You should also wipe down the work surface, interior walls and grille with an appropriate disinfectant for the type of work you are doing.

How long does a certification take?


Depending on the tests performed, a standard certification of a Class II, Type A1 or A2 BSC will generally take approximately 45 minutes to 1 hour. A standard certification of any Class II, Type B1, B2, or A2-Exhausted BSC will generally take approximately 1.25 to 1.75 hours. Additional time would be required to perform a degradation inspection, cabinet integrity test, decontamination or other maintenance.

What does field certification involve?


Field certification consists of required tests related to containment (personnel, product and environmental protection), and optional tests related to worker comfort and safety.

Required tests include:

  • Airflow velocity profiles (downflow and inflow)*
  • Airflow smoke patterns*
  • HEPA/ULPA filter leak test*
  • Site installation assessment tests*
    • Alarm functions*
    • Blower interlock*
    • Exhaust system performance* (proper exhaust duct negative pressure and canopy performance)
  • Cabinet integrity test (positive plenum cabinets only)

Worker comfort and safety tests include:

  • Lighting intensity*
  • Vibration
  • Noise level*
  • Electrical leakage, ground circuit resistance*, and polarity*

*Part of LTS Standard Certification Report
In addition to the above NSF/ANSI 49 recommends the lifespan of a unit be 15 years. Starting at age 16 Lewis Testing Services requires a degradation inspection be performed to reduce the safety risks that an aging unit generates.

When does my biosafety cabinet need to be certified?

Class I and II biosafety cabinets should be tested and certified at the time of installation and at least annually thereafter. In addition, whenever HEPA/ULPA filters are changed, maintenance repairs are made to internal parts, or a cabinet is relocated. More frequent field recertification should be considered for particularly hazardous or critical applications or workloads.

USP 797 requires testing on a semi-annual basis.

Who requires that my biosafety cabinet be certified?

The most important question is why you wouldn’t have your cabinet certified. Certification is both a safety and quality assurance function. Reestablishing the proper cabinet settings gives you the peace of mind that the cabinet will provide its specified personnel, product and environmental protections.

Recommendations and requirements to certify biosafety cabinets come from a variety of sources. All manufacturers and NSF International recommend field certification of biosafety cabinets at installation and at least annually thereafter. In addition, whenever HEPA/ULPA filters are changed, maintenance repairs are made to internal parts, or a cabinet is relocated. JCAHO has now required proper maintenance (certification) of BSCs. CDC and NIH state that it is “imperative” that Class I and II biosafety cabinets be tested and certified (BMBL, 5th edition) and NIH funded research grants require cabinet certification. Individual state boards of pharmacy require certification of biosafety cabinets used in pharmacies in accordance to USP 797. Finally, proper maintenance, including certification, of biosafety cabinets falls under the OSHA General Duty clause.

What are you actually certifying/testing?

A field certification confirms that an installed cabinet is operating in accordance with the field test specifications of NSF Standard 49 (if currently listed by NSF) or the manufacturer. Field certification does not include the microbiological challenge and cross contamination tests that are performed in the factory by the manufacturer.

Required Test Optional Test
  • Downflow velocity profile test*
  • Inflow velocity test*
  • Airflow smoke patterns test*
  • HEPA/ULPA filter leak test*
  • Site installation assessment tests*
    • Alarm functions*
    • Blower interlock*
    • Exhaust system performance* (proper exhaust duct negative pressure and canopy performance)
  • Cabinet integrity test (positive pressure plenum cabinets only)
  • Lighting intensity*
  • Vibration
  • Noise level*
  • Electrical leakage, ground circuit resistance*, and polarity*

*Part of LTS Standard Certification Report
In addition to the above NSF/ANSI 49 recommends the lifespan of a unit be 15 years. Starting at age 16 Lewis Testing Services requires a degradation inspection be performed to reduce the safety risks that an aging unit generates.