| Class I Biological Safety Cabinet | Yes, by drawing room air inward through the front opening and filtering the exhaust. | No. Room air passes over the work before entering the exhaust system. | Yes, when fitted with an appropriate exhaust filter and operated correctly. | Inward airflow across the work zone; filtered exhaust. | Approximately 900–1800 mm | Work involving potentially contaminated materials where product sterility is not required; aerosol-generating procedures with low product-protection needs. | Not appropriate for sterile culture preparation or procedures requiring protection of open samples from room contamination. | Usually ducted or configured with a filtered exhaust arrangement, subject to local design requirements. | Personnel and environmental protection at a comparatively simple installation level. | Personnel: High Product: Low Environment: High |
| Class II Type A1 | Yes, through inward airflow at the front opening. | Yes, through vertical HEPA-filtered downflow over the work surface. | Yes, through HEPA-filtered exhaust. | Recirculated HEPA-filtered downflow with inward inflow; minimum inflow is commonly around 0.38 m/s under applicable performance requirements. | Approximately 900–1800 mm | Routine microbiology, cell culture, clinical sample handling, and work with biological agents that do not generate significant quantities of volatile toxic chemicals or radionuclides. | Not designed for substantial volatile chemical use; exhaust arrangements must not allow hazardous vapors to accumulate in the room. | Often suitable for room-return exhaust, depending on the certified configuration and local regulations. | Balanced protection, broad availability, and relatively straightforward installation. | Personnel: High Product: High Environment: High |
| Class II Type A2 | Yes, through inward airflow at the front opening. | Yes, through vertical HEPA-filtered downflow. | Yes, through HEPA-filtered exhaust. | Part of the filtered airflow is recirculated inside the cabinet; inward inflow is commonly around 0.50 m/s under applicable performance requirements. | Approximately 900–1800 mm | General microbiology, diagnostic procedures, cell culture, molecular biology, and routine work with infectious materials. | Volatile toxic chemicals and radionuclides should generally be avoided unless the cabinet is specifically designed, certified, and properly exhausted for that use. | Can be room-return or canopy-connected, depending on the certified cabinet design; direct hard-ducting requires careful engineering. | Best all-purpose choice for many microbiology laboratories. | Personnel: High Product: High Environment: High |
| Class II Type B1 | Yes, through inward airflow and controlled cabinet airflow. | Yes, through HEPA-filtered downflow, with the work zone arranged to limit contamination risk. | Yes, with a dedicated exhaust path for the applicable airflow portion. | Partial exhaust of cabinet air through a dedicated duct; the remaining airflow is recirculated through HEPA filtration. | Approximately 1200–1800 mm | Selected procedures involving limited quantities of volatile toxic chemicals or radionuclides, together with biological materials, when validated by the laboratory. | Requires specialized design, dedicated exhaust, and strict operating procedures. It is not a universal substitute for a chemical fume hood. | Dedicated hard-ducted exhaust is normally required. | Combined biological protection with limited chemical-use capability. | Personnel: High Product: High Environment: High |
| Class II Type B2 | Yes, through inward airflow at the front opening. | Yes, through HEPA-filtered downflow across the work area. | Yes, through total exhaust of cabinet airflow after filtration and suitable exhaust treatment. | 100% exhaust cabinet; no internal recirculation of contaminated cabinet air. | Approximately 1200–1800 mm | Work combining biological hazards with significant quantities of volatile toxic chemicals or radionuclides, when specifically risk-assessed and approved. | Highest installation complexity, energy use, and operating cost among common Class II configurations. Loss of exhaust can require immediate work stoppage. | Dedicated, continuously monitored hard-ducted exhaust with building HVAC coordination. | Maximum combined biological and chemical containment within a Class II design. | Personnel: High Product: High Environment: High |
| Class III Biological Safety Cabinet | Very high, because the work zone is gas-tight and operated through attached glove ports. | High, when materials are transferred through validated pass-through systems and procedures. | Very high, with filtered exhaust and a closed work system. | Gas-tight enclosure maintained under negative pressure; air enters through supply filtration and exits through validated exhaust filtration. | Commonly 600–1800 mm, depending on modular system design | High-containment microbiology, specialized pathogen research, and procedures requiring maximum physical separation from the operator. | Restricted dexterity, slower material transfer, higher capital cost, and demanding decontamination and maintenance requirements. | Dedicated exhaust system with validated filtration and facility-level containment controls. | Maximum containment where the hazard assessment requires a fully enclosed cabinet. | Personnel: Very High Product: High Environment: Very High |
| Clean Bench / Laminar-Airflow Workstation | No. It is not intended to protect the operator from biological hazards. | Yes, for suitable non-hazardous work, through HEPA-filtered unidirectional airflow. | No, because the airflow may discharge aerosols toward the operator or room. | Horizontal or vertical HEPA-filtered unidirectional airflow across the work zone. | Approximately 900–1800 mm | Non-hazardous sterile assembly, media preparation without biological risk, and protection of clean components. | Must not be used for infectious agents, human clinical specimens, toxic chemicals, or procedures that generate hazardous aerosols. | Usually room-return; it is not a substitute for a biological safety cabinet. | Product cleanliness only, when personnel and environmental containment are not required. | Personnel: None Product: High Environment: None |
| PCR Workstation / Nucleic-Acid Workstation | Usually limited or none; protection depends on the specific design and workflow. | Yes, for reducing contamination during pre-amplification or clean nucleic-acid preparation. | Generally not intended for infectious or aerosol-generating biological work. | HEPA-filtered airflow, often combined with ultraviolet or chemical decontamination features where permitted by the design. | Approximately 600–1500 mm | Pre-PCR reagent preparation, DNA/RNA setup, and contamination control in molecular workflows. | Not a replacement for a certified biological safety cabinet when handling infectious samples or hazardous aerosols. | Usually no dedicated exhaust; verify the specific equipment design and laboratory risk assessment. | Prevention of amplicon contamination in molecular biology workflows. | Personnel: Limited Product: High Environment: Limited |