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Category: Laboratory Safety Blog

Changes in Class III Biological Safety Cabinets

Primary Containment and User Comfort

In the 1950’s when Class III BSC became widely used in the nuclear and defense departments the primary focus for design was on absolute containment, with little attention given to ergonomic/user comfort. Class II BSC became popular in the 1970’s and provided the user with an alternate means of primary containment. While Class II BSC do not provide the same level of user and environmental protection, based on a risk assessment they do have a rightful and very useful place in the biocontainment laboratory. In recent years with increasing work conducted at BSL-4 and the advent of samples containing mixed hazards or biological powders, there has been a significant resurgence in the use of Class III BSC in research, public health labs and with emergency responders. It was time for the Class III BSC to be improved upon and redesigned for diverse missions.
What has changed for Class III Biosafety Cabinets?
Lessons learned from Class II BSC & Biocontainment Lab Design

Lessons have been learned and applied regarding enhancements to ergonomics. Some have been taken from the design of Class II BSC such as use of:

10 degree tilt view panel to allow the user to lean into the screen for comfort and to reduce glare
adjustable deck height to provide more/user required leg room and accommodate work in a seated position
control panels that are positioned so they can be observed easily by the operator

Other innovations were developed to increase user range of motion and decrease fatigue, to include:

extra large, oval shaped gloveports to allow for natural arm positioning and extended reach
a wide rimmed gloveport to enable the user to rest their arms
the use of motion studies to determine the best locations for gloveports and to better size the work area (after all, what is the benefit of having a 33 inch (0.9 meter) deep BSC if you can not reach the back wall for manipulations or cleaning).

Other improvements were made when considering how containment labs are designed. Class II Biological Safety Cabinets really have not changed much in 30 years and still have right angles where the walls, deck, back panel and ceiling meet. This can pose a challenge when wiping down surfaces during decontamination. Per the CDC/NIH BMBL, WHO and Canadian Biosafety Guidelines, modern labs are constructed with coved or radiused joints to facilitate cleaning and prevent material from being trapped in 90 degree joints. Rounded joints were easily incorporated into new Class III BSC designs. Again, as in lab design, pass through boxes have been developed for BSC with interlocks and alarms to facilitate material transfer and prevent a accidental breach of containment.

Interestingly the flow of design information is now going from Class III BSC to applications in the laboratory…namely the use of Rapid Transfer Port embeds into laboratory walls. These mate with mobile Class III Biological Safety Cabinets to facilitate the transfer of animals from the BSC to the holding room.

Prospective improvements have few limits as most Class III BSC are custom designed…the next advances will likely combine user requirements and ingenuity and manufacturer problem solving and design expertise.

References

Biosafety in Microbiological and Biomedical Laboratories (BMBL) 5th Edition (Download PDF)

Public Health Agency of Canada’s Laboratory Biosafety Guidelines (Download PDF)

World Health Organization Biosafety Manual (Download PDF)

The most recent edition of CBRNe WORLD Magazine includes a highly informative article on the rationale for the procurement and deployment of mobile laboratories. The article, authored by Monica Heyl, discusses the use of mobile labs by first responders, military, law enforcement and civil support teams.  Ms. Heyl describes a range of applications for these units:
“Mobile laboratories can be integrated to fill a wide variety of challenges: sample receipt, screening and evaluating suspect unknown materials, environmental health protection and remediation, narcotics analysis and confirmation of clandestine laboratories. They can respond to catastrophes, terrorism, and a myriad of other actions in theatres of conflict or on our own homelands.”
The CBRNe World article also discusses the critical role of proper engineering controls in mobile laboratories, stating that:
“Engineering controls (primary and secondary) become vital to sample collection, reception, preparation, analysis and spent effluent that could contaminate the environment. Robust engineering controls to include redundant and hybrid filtration systems, breakthrough monitors and backup uninterrupted power are only as good as the quality assurances associated with the development, building, manufacturing and testing of such safeguards.”
The article, “Mobile Laboratories: Do They Know Their Rank,” by Monica Heyl is available in the Spring 2010 edition of CBRNe World Magazine.
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Monica Heyl is an internationally recognized mobile laboratory expert.  She Co-founded,  Monica Heyl and Associates after retiring from the United States Department of Defense, US Army. This firm specializes in field analytical solutions particularly in high hazard environments. Her 35 years of service included a range of leadership positions, including: US Army Senior Leader; Director of International Programs and Leader of the US Army’s Mobile Laboratory & Kits (ML&K) Team and the Advanced CBRNE Training Team.
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 CBRNe World  is a internationally distributed quarterly publication based in the UK. The magazine is geared for professionals in a range of fields where their work involves “planning for or responding to a chemical, biological, radiological, nuclear or explosives (CBRNe) threat or incident.”  According to the publishers, the CBRNe World content spans the “divide of operational and scientific, it brings together opinion formers from the world of civil response, military leaders, academia, government agencies, research labs and industry.”

The Laboratory Safety Blog has been developed to open a dialog and address a variety of topics regarding biological safety. We will cover topics ranging from general issues in biosafety and primary containment to Class III Biological Safety Cabinets as well as innovations in biosafety engineering.
The Laboratory Safety Blog serves as a professional forum for biosafety professionals and industrial hygienists, scientists and technicians, architects and engineers, and other professional groups with an interest in laboratory safety. Based on questions we receive on a regular basis, some of the topics we will discuss in the near term include but are not limited to:
Defining the standard Class III Biological Safety Cabinet (BSC).
Identifying methods to transfer materials.
Innovations in transferring lab animals and never breaking containment.
Ergonomic improvements of Class III BSC over the past few years.
Factors involved in choosing gloves, and an overview of glove availability.
Methods of decontaminating a Biological Safety Cabinet.
How to prepare a biosafety cabinet for gaseous decontamination.
Determining the efficacy of the decontamination process.
Explaining how a ventilated or non-ventilated pass through box works and the advantages/disadvantages of each.
Various discussions on mobile labs, modular labs and their applications.
Discussion of the guidelines for manufacturer and field testing of Class III BSC…and their differences.
Development of best practices in Class III BSC field performance tests.
We invite reader questions and responses as part of a mutually beneficial educational process to strengthen a collective knowledge of biosafety, identify biosafety engineering products that are needed by user groups, and foster a safer, healthier and more productive workplace environment.

These recommendations were developed by comparing the various performance tests identified in the standards described in the past two blogs, in an attempt to provide guidance on the development of a comprehensive performance field test. Consideration has also been given to those factors that may affect the ability to conduct a performance test using values in any given specification. Selection of ‘required’ tests as opposed to ‘optional’ tests should be based on a risk assessment that considers safety as well as the work being conducted. Influences to the system include temperature, humidity, altitude (as compared to factory readings), and barometric pressure. These factors can have a large effect on system readings. Routine work with animals as opposed to cell culture may justify measuring noise levels and considering more stringent control of decibels produced. A nuisance noise level to humans may be loud enough to have adverse effects on some species of animal.
Annual tests to strongly consider* include: Visual inspection*; Cabinet Integrity Test (Leak rate)* or Negative Pressure Test (rate of rise test) or Positive Pressure Test (pressure decay test); HEPA Filter Leak Test*; In-Rush Protection Test (loss of glove); Air Flow Test (smoke pattern tests); Alarm Tests (airflow and interlocks)*; and measuring* Illumination, Vibration, Electrical Continuity, and Noise level.
Visual Inspection
Turn on the fluorescent light. Visually inspect gloves, bag-out assembly, pass through chambers and all gaskets and o-rings for signs of holes, cracks, wear or damage.
Inspect the view screen for cracks or damage, and ensure the dunk tank is filled to the appropriate level with the correct decontaminating agent. Replace any worn or damaged parts and ensure all components of the Class III BSC are in proper order before conducting work.
Leak Rates – Factory Testing vs. Field Testing
The BMBL and other standards describe acceptable leak rates. In the absence of one internationally or nationally accepted standard, it is important to base field testing on technically proven or sound leak rates to promote safety and to consider the practicality of conducting the test on-site.
The original factory test specified in the Lab Safety Monograph allows for no loss greater than 1 x 10-5 cc/sec with 100% tracer gas in the factory setting. In the field it is impractical to test using 100% tracer gas, and the test is performed using 1% tracer gas with the leak rate adjusted to 1 x 10-7 cc/sec to compensate for the two log reduction in gas. The use of a helium leak detector (mass spectrometer) is typically used to measure and locate leaks. Pressure tests can be used in lieu of the use of helium gas.
Differential Pressure
Differential pressure of 0.5” water gauge may not be adequate to accommodate glove use in small cabinets. The physical act of pulling glove into and out from the cabinet can cause swings in the internal differential pressure and could trigger pressure alarms and could lead to an unsafe condition. However, high differential pressure can result in hard to maneuver gloves and may cause safety concerns due to increased resistance to arm movements. Choose an operational differential pressure that works for the design of the Class III BSC. Treat the 0.5” wg recommendation of the BMBL as a minimum.
HEPA Filter Testing
Filters can be tested for integrity using a scan or probe method. Scan testing of HEPA filters is a better method of discovering filter leaks and identifying their location than using the probe method.
The BMBL and other standards specify testing challenge by Di-Octyl Phthalate (DOP), though due to risks associated with DOP it has largely been replaced by mineral oil and Poly Alpha Olefin (PAO). PAO has similar characteristics of DOP and creates a consistent particle size. These materials generate an appropriate concentration and size dispersion aerosol challenge using a Laskin Nozzle at a defined flow rate. It is important to note that these challenge materials are not interchangeable and the photometer must be calibrated to the particular challenge material used.
Illumination, Vibration, Electrical Continuity, and Noise Level Tests
These tests can be conducted as described in NSF 49. A decision should be made as to whether these tests are optional (for data collection) or mandatory. If they are mandatory the failure of any of these tests would warrant stopping work with the unit until the appropriate maintenance is performed. It is clearly beneficial to conduct the tests at a minimum to demonstrate any performance trends that indicate maintenance is needed.
Equipment Calibration and Certifier Credentials
All instruments used to certify Class III BSCs must be calibrated and NIST (or national equivalent) traceable. The calibration should be done on an annual basis. Certificates of calibration should be available from the certifier. NSF qualifies Class II BSC certifiers by both a written and practical test and a requirement for attending Continuing Education every 5 years with retesting after 10 years. However, there is no regulating authority or set of training or experience requirements for personnel certifying Class III BSCs. NSF does specify that if an individual in an organization performs Class III BSC certifications they must be NSF accredited, but this is for Class II BSC.
There is no one requirement or standard for annual field testing of a Class III BSC, and a risk assessment and analysis of the work being performed should help to drive the certification process. The institute biosafety professional or a qualified biosafety consultant should be involved in developing the certification requirements. The institute must be provided a copy of all data and readings gathered by the certifier for a matter of record as well as for future trending data and definitive proof that a certification was actually conducted.
References
1. NSF 49 Class II (Laminar Flow) Biosafety Cabinetry, NSF/ANSI 49-2008 Edition: 11th
2. Guideline For Gloveboxes, Third Edition AGS-G001, February 2007
3. Biosafety in Microbiological and Biomedical Laboratories (BMBL), 5th Edition, 2007 NIH/CDC http://www.cdc.gov/od/ohs/biosfty/bmbl5/bmbl5toc.htm
4. Laboratory Biosafety Guidelines, 3rd Edition, 2004, Public Health Agency, Canada, http://www.phac-aspc.gc.ca/publicat/lbg-ldmbl-04/pdf/lbg_2004_e.pdf
5. Laboratory Safety Monograph: A Supplement to the NIH Guidelines for Recombinant DNA Research, 1979 http://www.ors.od.nih.gov/ds/pubs/bsc/contents.html
6. Biotechnology- Performance criteria for microbiological safety cabinets; BS EN 12469:2000/EN 12469:2000, 2000, Dandy Booksellers Ltd.

The last blog addressed industry accepted standards for performance testing of Class III Biosafety Cabinet in the US. This blog focuses on other Internationally accepted standards. These standards contain some areas of overlap with US standards and in other areas provide supplemental information.

British/European Standard BE EN 12469:2000/EN 12469:2000, 2000 (1) :
Class III BSC has a completely enclosed workspace and manometer to show pressure drop (manometer range of -500 Pa to + 500 Pa), (500Pa =2”wg)
Supply air single HEPA, exhaust air double HEPA filtered. Each exhaust filter must be able to be independently tested

Leak tightness: /= to 0.7 m/s with one glove removed, (0.7 m/s =138 ft/min)

Public Health Agency Canada, 2004, (2):
PHAC Laboratory Biosafety Manual 3rd Edition 2004: Document Submission Requirements for the Recertification Performance and Verification Testing of Containment Level (CL) 4 Laboratories in Accordance with the Laboratory Biosafety Guidelines, 2004, Public Health Agency of Canada (and where applicable, Containment Standards for Veterinary Facilities, 1996, Canadian Food Inspection Agency)

Class III BSC to be tested in accordance with:
BS EN 12469:2000: Biotechnology- Performance criteria for microbiological safety cabinets (2000); British Standards Institute

Laboratory Safety Monograph: A Supplement to NIH Guidelines for Recombinant DNA Research (1979); National Cancer Institute Office of Research Safety and the Special Committee of Safety and Health Experts.
Acceptance criteria: measured leakage from any point in the cabinet shall not exceed a leak rate of 10 X 10-7 cc/sec at 750 Pa (750 Pa=3″ wg).

Provide the calibration certificates for the equipment used for the verification.
The final blog in this series will describe ‘best practices’ in field testing (annual on-site recertification) the Class III BSC. As there is no NSF 49 Standard or other regulation that addresses annual retesting, the next blog will consider all of US and International Standards and provide a recommendation for a comprehensive test procedure based on the various standards.

References:
Biotechnology- Performance criteria for microbiological safety cabinets; BS EN 12469:2000/EN 12469:2000, 2000, Dandy Booksellers Ltd.
Laboratory Biosafety Guidelines, 3rd Edition, 2004, Public Health Agency, Canada

In biosafety training programs, it is critical that students develop a familiarity with biological safety equipment. In courses and workshops, this can take the form of industry-insider trainings, interactive exercises as well as hands-on experience with the equipment. Industry can play an important role in biosafety training. This goes beyond demonstrating equipment at trade shows and conferences.

Germfree’s Class III BSC Training Unit at ABSA Course: “Fundamentals of the Class III Biosafety Cabinet”

Class III Biological Safety Cabinets: Importance of Hands-on Training
Practical training is particularly useful for students that plan to work in high containment situations. While many students have access to Class II Biosafety Cabinets, too few are able to get hands-on experience with a Class III Biological Safety Cabinet. Class III BSC’s require a familiarization with a wide range of equipment features and configurations such as: Gloves & Gloveports, Pass-throughs / Airlocks, Rapid Transfer Ports, Autoclaves, Decontamination Systems, etc.

Germfree maintains a Class III BSC training unit at their headquarters. Germfree also participates in student training programs with other facilities, providing institutions with Class III BSC’s and other bio-containment equipment to give their students hands-on experience and training in proper technique. For example, Germfree’s Biological Safety Cabinets have been used for training in university settings such as The Emory University Science and Safety Training Program as well as workshops in conference settings such as ABSA’s Annual Biological Safety Conference.

TRAINING FROM THE ROAD: This coming week, Cliff Colby from Germfree will take to the road for a variety of presentations and visits in the greater Washington D.C. and Baltimore areas.

He will be visiting various U.S. military and governmental agencies as well as the University of Maryland and Johns Hopkins University. While in Baltimore, Cliff will also be teaching a course at The BioTechnical Institute of Maryland (BTI). The workshop he is presenting at BTI is The Theory, Practice And Proper Use Of A Class II BSC. This course will cover the practical aspects of properly using a Class II Biological Safety Cabinet.

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Cliff Colby is VP of Sales at Germfree. He has more than 12 years experience as a Biosafety Instructor. He has also worked extensively on multi-media biosafety training materials. And if you want to discuss applications that require chemical containment, his background as a Chemist will also come in handy.
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The BioTechnical Institute of Maryland provides training for students that want to enter the biotech field. According to the BTI website, the institute “fills a need for specialty scientific training of entry-level biotechnicians for employment in Maryland’s rapidly expanding biotechnology industry. The BTI Laboratory Associates Program provides tuition-free training in basic laboratory skills to bright, ambitious, unemployed and under-employed Maryland residents. “

Class III BSC: Performance Testing Standards

There are several prominent industry accepted standards for performance testing of Class III Biosafety Cabinet in the US. These standards contain some areas of overlap, and in many cases one standard contains performance related information not contained in the other standards. The information below provides a brief summary of the highlights as they apply to criteria for US performance testing. A subsequent blog will address international performance standards.

1. National Sanitation Foundation Standard 49, 2008:
It is a gas-tight (no leak greater than1x10-7 cc/sec with 1% test gas at 3 inches pressure wg) enclosure with a viewing window that cannot be opened without the use of tools or locks.
Access for passage of materials into the cabinet is through a dunk tank, that is accessible through the cabinet floor, or double-door pass-through box (e.g., an autoclave, rapid transfer port, pass through chamber)
Both supply and exhaust air are HEPA filtered on a Class III cabinet. Exhaust air must pass through two HEPA filters, or a HEPA filter and an air incinerator, before discharge to the outdoors.
Airflow is maintained by an exhaust system exterior to the cabinet, which keeps the cabinet under negative pressure (minimum of 0.5 inches of water gauge.)
The exhaust fan for the Class III cabinet is generally separate from the exhaust fans of the facility ventilation system.

2. American Glovebox Society, 2007 :
Airflow monitoring: should be provided i.e. magnahelic guage
Differential pressure is industry specific: maintained at 0.2-1.5 inches wg
Glovebox flow rate through an open glove port: 125 +/- 25 linear ft/min
Glove inspections should be performed: no firm guidance on frequency
Leak detection: internal pressure is stabilized at -1.5 inches wg and temperature, pressure and time are recorded until pressure drops to -0.6 inches. Leak rate can not exceed 0.5% glovebox volume per hour.
There should be qualified trainers and operator training.

3. Laboratory Safety Monograph: A Supplement to NIH Guidelines for Recombinant DNA Research, 1979:
The Class III biological safety cabinet is a totally enclosed ventilated cabinet of gastight construction.
Class III cabinet is maintained under negative air pressure of at least 0.5 inches water gage. Supply air is drawn into the cabinet through HEPA filter. The cabinet exhaust air is filtered by two HEPA filters installed in series.
The exhaust fan for the Class III cabinet is generally separate from the exhaust fans of the facility ventilation system.
Material transfer through double-door sterilizers and dunk baths with liquid disinfectants.
Should be certified (i) after a new cabinet has been purchased and installed, but before it is used, (ii) after it has been moved or relocated, and (iii) at least annually.
Negative pressure inches wg: >0.05
Leak tightness: leak rate <1 x 10 -5 cc/sec at 3”wg pressure using halide tracer gas
Small leaks can be detected by soap solution testing
HEPA certification: annual or as needed above
Verify and calibrate magnahelic gauge and test audible alarm

Class III BSC: Best Safety Practices & Engineering

Taken together there are a few recurrent points and statements that reflect best safety practices and engineering. The Class III Biological Safety Cabinet must be leaktight (this implies very solid construction, durability and seals), and operate at -0.05 ” wg relative to the lab. Exhaust air is filtered through 2 HEPA filters in series, with supply air filtered by 1 HEPA filter. Alarms should be present to warn the user of BSC failure, and the user should be trained in te correct operation of the unit. The BSC and its HEPA filters should be field tested annually, but components that are prone to wear (i.e. gloves, gaskets, etc) should be inspected as part of a pre-operational inspection. As perfromance tests in the field are not codified by NSF 49, recomendations on what types of field testing should be perfromed annually will be provided in a later blog.

References:
1. NSF 49 Class II (Laminar Flow) Biosafety Cabinetry, NSF/ANSI 49-2008, Edition: 11th
2. Guideline For Gloveboxes, Third Edition AGS-G001, February 2007
3. Laboratory Safety Monograph: A Supplement to the NIH Guidelines for Recombinant DNA Research, 1979 (PDF)

Pass through chambers provide an easy way of moving supplies and materials in-to and out-of the Class III Biological Safety Cabinet. There are a few options to consider with these devices. To begin with, their interior surfaces should be coved for ease of cleaning, and the exterior of the chamber should not extend into an area where there is foot traffic. The doors must provide an airtight seal to allow of gaseous/vapor decontamination and prevent the leakage of air from the Class III BSC into the laboratory.

Doors should also be electronically interlocked to prevent a breach of containment. If they are not electronically interlocked there should be either an alarm light or audible warning to let the user know when one door is open. If they are interlocked, consideration should be given to an override switch that is positioned in a location that would require a deliberate motion for activation. At some point pieces of equipment or tools that exceed the size of the pass through may need to be introduced or removed, hence the desire for an interlock override. This is important if the Biological Safety Cabinet does not have an integral autoclave, or the item can not be passed out through the autoclave.

Class III Biosafety Cabinets Pass Through Chamber: Choosing the Right Size

How do you decide what size pass through is needed? The user(s) should take measurements of the equipment/supplies that have the greatest dimensions in terms of height, length and depth that will be used on a regular basis. How long are the pipettes? How tall is the animal isolator(s)? What are the dimensions or the microfuge? The interior measurement of the chamber when both doors are closed, should accommodate the equipment with a little room to spare.

Class III BSC Pass Through Chamber: Ergonomics

Size, shape and location of the pass through is also impacted by ergonomics. Recall, the user must reach into the BSC through a gloveport and enter the pass through at a slight angle. Items being removed must be within the users grasp, or the user will need a tool (tongs, preferably with a rubberized gripping surface) to reach further back to retrieve supplies. Thought has to be given to what materials are in the front of the chamber near the users hand (media, samples, squeeze bottle with decontaminating solution, etc), and what can reasonably by accessed with tongs (absorbent toweling). It is actually not so easy to get a good grip with tongs and remove pipette tips from the back of a pass through chamber. Optimally, the user should be able to wipe down the surfaces with toweling after the chamber has been sprayed with a decontaminant.

There is no rule that says a user can only have two doors on the pass through. Many Class III Biosafety Cabinets constructed for use by military and security forces have an additional door built into the chassis of the mobile laboratory that leads from the outside in-to the Class III BSC. This prevents the sample collector or person delivering the sample from having to enter the laboratory. The number of doors and what they access is driven by the mission and user requirements.

HEPA Filtered Ventilated Pass Through Chambers

Based on requirements the user may also opt for having a HEPA filtered ventilated pass through chamber. Ventilated chambers are commonly seen when a laboratory may receive a mixed sample that could contain a volatile chemical compound, but are also used when the pass through is the primary method of removing samples and other items from the Class III BSC that may not otherwise be removed via the dunk tank (animals in cages, plated samples, experiments that need to remain upright, etc). Some users prefer the added safety of knowing the air in the chamber has been purged, and the pass through chambers exhaust system creates inward airflow upon opening the door to the lab. Airflow varies with the airflow rate in the chamber of the BSC and the cubic volume of the interior of the pass through chamber. Even if the chamber is ventilated, material leaving the Biological Safety Cabinet should be surface decontaminated and placed in a secondary container which is sprayed with decontaminant before being placed inside the pass through. If a non-ventilated chamber is used, the same procedure as above can be followed with the addition of spraying the interior of the pass through chamber to facilitate the settling of any aerosols in the chamber. Whether ventilated or not, at the end of work, or upon a spill in the chamber, the pass through chamber must be decontaminated.

What type of airflow should be used in a Class III BSC? Is higher velocity better?
Class II BSC vs. Class III BSC Airflow

Unlike Class II BSC which employs laminar flow to protect personnel, the Class III Biological Safety Cabinet does not have an open sash in the front, hence does not require laminar airflow to provide personnel protection. The main consideration for laminar air flow in a Class III BSC is for product protection. Laminar flow could be important if an internal process generates copious amounts of aerosol, when work is conducted with fine powders, or if there is a risk of cross-contamination between different procedures being performed in the cabinet. Laminar air flow has a set mass airflow where clean HEPA filtered air comes from one direction at a given speed to entrain particles and carry them directly to the exhaust HEPA. The velocity can be very low, as low as 30 ft/min. However, note that 30 ft/min may cause extremely fine powders to become aerosolized.

Generally, Class III Biosafety Cabinets use turbulent air flow designs. In a turbulent airflow design clean HEPA filtered air is continuously supplied to the cabinet where it dilutes the concentration of aerosolized particles by carrying them to the exhaust HEPA. This is a more passive mechanism of particle removal as compared to that of the air current generated when laminar airflow is established. The rate at which the particles are exhausted depends on the supply velocity (which is equal to the exhaust velocity). In reality, work in a Class III BSC is conducted methodically and carefully. Most activities conducted in a Class III BSC produce minimal aerosols so turbulent airflow is the norm. Turbulent airflows are easily adjustable and can have lower air velocity than those required to maintain laminar airflow, hence can pose less of a problem when working with fine powders.

Another question that comes up is whether the Biological Safety Cabinet should be operated at high airflow velocity to remove particles more rapidly. Typically higher velocity airflows are used when working with volatile chemicals, but not with microbiological agents or toxins. High velocity airflow can inadvertently, and very effectively, cause powders to be disseminated throughout the interior of the BSC.

A decision regarding whether laminar or turbulent airflow is needed, and the velocity of supply air required for operations should be made based on the anticipated work and user needs. Use of laminar air flow in a Class III Biosafety Cabinet will typically increase the volumetric supply and exhaust airflow as compared to a BSC using turbulent airflow. Higher velocity airflow will similarly increase volumetric supply and exhaust as compared to maintaining low velocity airflow. Increased exhaust flow rate from the Class III BSC should be considered during facility and HVAC design if the cabinet is connected to facility supply air and is to be exhausted out of the building.

The post from January 10thon Mobile and Modular Laboratory Platforms generated an interesting question.
The question was,
‘If we can build the BSL-3 lab with local tradecrafts, but do not think there is local experience in HVAC construction and controls, is it possible to purchase the HVAC system in a prefabricated package for delivery and installation’?
Yes, it is possible to purchase a prefabricated HVAC system with controls to support a Biosafety Level-3 lab. It will require coordination between the team working on the lab, to include the architect, engineer, and project manager with the supplier of the HVAC system. The supplier in essence is acting as the mechanical engineer and will need access to drawings and specifications to:
identify penetrations, connections and site survey details,
size the system to accommodate heating and cooling load data,
plan for cascading airflow, sensor and damper placement,
engineer a system that does not conflict with those services in adjacent spaces in the existing building (i.e. building automated system),
harmonize systems when needed (i.e. security control systems, BAS),
coordinate electrical and plumbing connections and specifications, and
coordinate other aspects related to the HVAC and associated systems during facility design to ensure smooth construction, commissioning and acceptance phases.
The HVAC system and its control system (BAS) are the most often cited Achilles heel of containment laboratories. Purchasing a prefabricated HVAC system that meets WHO, CDC or other recognized design recommendations is a very suitable strategy when there is a lack of tradecraft with experience in Biological Safety Level 3 construction, and in cases where the laboratory is in a retrofit space that can not be accommodated/reliably accommodated by the existing building system. It can be significantly less expensive than trying to retrofit an existing building HVAC system and has the added benefit of allowing operations to continue in the existing building during construction of the addition or renovation of the space.
Experience: HVAC for BSL-3 Containment Labs
If an organization does choose to purchase a prefabricated HVAC, it should be one designed and built by companies that can provide proof of construction of several functional BSL-3 containment laboratories . Companies that specialize in clean rooms and have no true expertise in biocontainment typically and catastrophically misapply HVAC and BAS clean room concepts to containment labs. It is important to ensure companies have biocontainment experience similar to your project. Components of HVAC for BSL-3 containment include but are not limited to welded leak tested stainless steel exhaust duct and HEPA housings, HEPA housings with scan test and decontamination ports, airtight dampers for room decontamination, and rapidly responsive air volume control valves and a BAS to prevent sustained pressurization of the lab during HVAC failure.
The goal is to have a working building that provides a safe work environment to staff and the community and can be maintained by personnel on-site. To that end, the company should act as the single source that has responsibility for the systems and subsystems and ensuring once connected to the lab, the system performs per design intent. To every extent within reason the system should be sustainable and serviceable within the region. While specialists may be required to decontaminate and replace HEPA filters within the housings, the system should be designed and constructed such that for example, standard air-conditioning and heating components can be worked on locally. The planning done on the front end of the project, and selecting an experienced containment company will provide huge dividends throughout the construction process and life of the building.

Three events have come together in the past few years that codified a need for rapidly deployable, mobile and cost effective containment equipment. First, there was recognition that many regions and countries in the world did not have adequate infrastructure, reliable power, or primary containment to provide a safe environment when working with emerging, re-emerging and dangerous infectious agents. In the US and elsewhere following the 2001 anthrax letters Public Health Labs and First Responders began experiencing an increase in their mission scope to collect, transport and perform analysis on unknown samples that may contain biological or chemical hazards. That mission had increased significantly due to copycat, hoax and criminal activity. In the same timeframe, advances in biomedical research created a need to move samples, animals and materials from room to room, or into and out of imaging suites and equipment while maintaining containment. In response to these needs portable Class III Biosafety Cabinets, flexible film isolators and compact, easily deployable hybrids were developed and refined.

Portable Class III Biological Safety Cabinet

Small, bench top units were developed that provide safe, effective and affordable primary containment (i.e. SEA) enabling flexibility for laboratory use or field deployment. It was originally developed for diagnostic screening of unknown and highly pathogenic samples in facilities, laboratories or field settings that lack reliable secondary containment controls. The closed system decreases the chance of aerosol escape, resultant accidental exposure and potential laboratory acquired illnesses.
In animal research, portable battery powered Class III BSCs are increasingly being used to move animals from holding rooms to procedure rooms. The supply is single HEPA filtered, the exhaust is double HEPA filtered as required by the CDC (Download BMBL 5th Ed. pdf). By use of large RTPs integrated into transporter carts of Class III design, the walls of animal holding rooms, and stationary Class III systems, scientists can safely transport exposed animals from holding rooms to procedure areas equipped with devices such as magnetic resonance imaging (MRI), positron emission tomography (PET), and other non-invasive scanning devices. The systems reduce personnel and environmental exposure and reduce the time the animal must be handled and anesthetized.

Transportable Class III BSC

Transportable Class III Biological Safety Cabinets are used in Public Health Laboratories for the receipt of unknown hazardous samples associated with chemical or biological terrorism or criminal activities. Workers use the transport BSCs to move the unknown hazardous sample from the loading dock area or other delivery site used by the First Responder, to the containment lab without risking contamination of non-contained and public areas, as well as the containment lab itself.
Taken together, the advent of the use of transport and mobile Class III BSCs provides a significantly safer way of moving and handling infected animals or unknown samples than any past capability.

Flexible Film Isolator

The negative-pressure flexible-film isolator is a self-contained primary containment device that provides maximum protection against hazardous biological materials. Isolators can be placed on a counter top or on a mobile cart. The workspace is enclosed in a transparent polyvinylchloride (PVC) film that suspended from a plastic or steel framework. Like Class III BSC, the supply air passes through one HEPA filter and exhaust air passes through two HEPA filters.
WHO recognizes the double HEPA exhaust obviates the need to duct exhaust air outside the building. Flexible-film isolators are used frequently and very successfully in animal containment, field work and other instances where it is not feasible to install or maintain conventional BSC. Hybrids (semi-flexible film isolators) exist where some of the panels are made of a rigid material such as polycarbonate, and typically the front panel is soft PVC.

Deployable Isolators

The deployable isolator unit is a self-contained negative pressure filtration system that operates on two standard D cell batteries. Supply air is HEPA filtered. Exhaust air is double HEPA or double HEPA and carbon filtered. All filters are readily available and easily replaceable by First Responders and those involved in field collection and preliminary screening and triage. It is a rapidly deployable, light-weight, disposable system that comes in a compact transport case and sets up much like a dome tent. The isolator is made of durable 15mil polyurethane to withstand field use, repeated assembly/disassembly, and can be assembled and operational within minutes for on-demand use requirements. Large samples and equipment are introduced through a zipper system similar to those on a BSL-4 suit. Sampling ports are provided for use with external detectors and analytical equipment.
The diversity in containment equipment is almost limitless and depends on user requirements and design team innovation and advances in materials.