Laminar flow enclosures and biological safety cabinets illustrate differences in airflow management as it pertains to the types of procedures conducted within them.
Laminar flow enclosures are used when process protection is paramount in applications wherein the operator and lab environment are not exposed to hazardous chemical or biological agents. Capture of airborne contaminants such as dust or microbes is crucial to successfully performing sterile compounding and intravenous bag mixing, optics and semiconductor wafer manufacturing, and cell culture media preparation, to name a few. Mystaire offers the MY-ISO 5 Vertical Laminar Flow Workstation and the CleanPrep+ Horizontal Laminar Flow Clean Bench for these procedures. The difference between these two products lies in laboratory air being drawn from the top of the workstation or from the rear of the clean bench. In each case, the laboratory air is subsequently filtered through HEPA filters, allowing clean air to flow in nonturbulent, parallel layers either vertically or horizontally over the process and out of the front sash. Both products are rated at ISO-5, from ISO-14644 2020 (equivalent to FED-STD 209E Class 100), which specifies the total number of particles of sizes ranging from 0.1 μm to 1 μm per cubic meter after filtration. As an example, unfiltered office air is classified as ISO-9 with 35,200,000 particles per cubic meter at ≥ 0.5 μm, while ISO-5 provides 10,000 times fewer particles.
Biological safety cabinets (BSCs) differ from laminar flow enclosures in that operator, environmental, and/or process protection is built into these products, depending on their class. These are designated as Class I, II, or III depending on the degree of hazard protection to personnel or process. Class I, similar to a ductless or filtered fume hood, draws lab air into the cabinet, directing any aerosols or particulates generated during a procedure away from the operator into a HEPA filter that returns the purified air to the lab. The objective is operator and environment, not process protection. Class II BSCs provide both operator and process protection by creating a partial barrier: incoming air is drawn into a grille just within the cabinet entrance, countering the HEPA-filtered air directed downward unidirectionally as a laminar flow into the cabinet work area. This class is further divided into A1, A2, B1, and B2 types based on airflow route and velocity, HEPA filter position, the nominal percentage of recirculated vs. exhausted air, and HEPA-filtered exhaust routing (internal to the lab or external). Class III BSCs incorporate glove portals and decontamination chambers to handle the most dangerous microorganisms in specialized laboratories. All BSCs must be certified for cabinet integrity and for specified air inflow, distribution throughout the cabinet, and exhaust at the time of installation, when moved, or when HEPA filters are changed, and at least annually1.
The selection of a particular BSC class for a project utilizing microorganisms, blood, or other potentially infectious material is derived from a risk assessment that evaluates the transmissibility and infectivity of the microorganism, severity of resulting disease, availability of vaccines or treatments in case of exposure, and the nature of the laboratory procedure(s) to be completed. Importantly, this assessment includes types of personal protective equipment, decontamination procedures and equipment, facility requirements, additional engineering controls for airflow management, and other risk factors. This risk assessment is most often used to define the Biological Safety Level (BSL) for a specific laboratory procedure, microorganism, culture, and/or sample. In the United States, biological safety levels defined by the Centers for Disease Control and Prevention2 are generally used to identify the appropriate measures required to protect workers and the environment in biological laboratories. All laboratory handling of biological materials, regardless of BSL, must meet federal, state, local, and institutional rules and regulations regarding laboratory safety.
Currently, there are four biosafety levels, ranked in order of increasing hazard to health and the environment, from BSL-1 (least hazardous) to BSL-4 (most hazardous). In general, a BSL-1 procedure requires basic PPE, employs standard microbiological practices with associated safety procedures, such as daily surface decontamination, but may not require the use of a BSC. Well-characterized nonpathogenic bacteria that do not cause disease in healthy adults, such as Escherichia coli K12, may be considered BSL-1 microorganisms. The BSL-2 classification involves handling moderate-risk infectious agents, such as Staphylococcus aureus, which can cause disease if inhaled, ingested, or exposed to the skin. Facilities performing BSL-2 procedures must meet additional requirements, including, but not limited to, being equipped with eye-wash stations, hand-washing sinks, doors that close and lock automatically, and decontamination equipment. BSL-3 describes agents that cause potentially fatal infection through inhalation exposure, such as anthrax. Increasing engineering controls, such as airflow into the lab, a hands-free sink and eyewash near the lab exit, and PPE requirements (including the potential use of respirators), build on the BSL-2 standards. The final classification, BSL-4, is reserved for lethal, exotic agents such as the Ebola virus that are readily transmissible and for which no treatment or vaccine is available. Work with these agents requires highly specialized laboratories equipped with comprehensive engineering controls and Class III BSCs. As of 2023, there are only 51 operational labs worldwide capable of handling BSL-4 agents3.
Class II BSCs can be used for BSL-1 through BSL-3 operations, provided all additional PPE, safety practices, facility, and engineering requirements, etc., for a given BSL are met. The Mystaire CleanPrep™ BSC is a Class II A2 biological safety cabinet that offers a full suite of engineering features to provide concurrent operator and process protection. A microprocessor monitors sensor data from the air management system, comprising the inflow velocity rate, the downflow ULPA-filtered airflow rate into the work area, and the pre- and post-pressure differentials for the downflow and exhaust ULPA filters. These four metrics are displayed on the touchscreen, with visual and audible alarms alerting to deviations from preset values of 100-110 feet per minute (fpm), 60-70 fpm, 80-120 pascals (pa), and 80-120 pa, respectively. Onboard diagnostics evaluate the system and furnish an optical display of performance. The ULPA filters provide enhanced particle containment, with a minimum efficiency rating of 99.9995% for particles with a diameter of 0.12 microns or larger. Additional features, such as UV irradiation, a motorized sash with UV inhibitors, and stainless-steel surfaces, augment the CleanPrep BSC's safety features. For applications that require filtered and then exhausted to the atmosphere, the CleanPrep BSC can be fitted with a canopy and connected to the building exhaust system.
Mystaire offers laminar flow products that meet project requirements. When process protection is exclusively needed, the HEPA-filtered MY-ISO 5 Vertical Laminar Flow Workstation and the CleanPrep+ Horizontal Laminar Flow Clean Bench are suitable. The Mystaire CleanPrep BSC affords the requisite features for biological investigations when combined with all necessary regulatory, safety, facility and engineering controls established through a thorough risk assessment program.
1. CFR 1910.1030(e)(2)(iii)(B); see also NSF/ANSI 49 Field Certified for testing and accreditation.
2. “Biosafety in Microbiological and Biomedical Laboratories”, 6th Edition, June, 2020. Centers for Disease Control and Prevention, National Institutes of Health. https://www.cdc.gov/labs/bmbl/index.html
3. “Global BioLabs Report 2023”, 2023. King’s College London and School of Policy and Government, George Mason University. https://www.kcl.ac.uk/warstudies/assets/global-biolabs-report-2023.pdf