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Biosafety Cabinets Explained: Class I, II and III, and How to Choose a Class II Type A2

  • Aug 19
  • 7 min read

Key Summary

A biosafety cabinet protects you, your sample and the room. A laminar flow cabinet protects only the sample. If you work with anything infectious, that distinction decides the purchase, and getting it wrong puts the operator at risk.

Class II Type A2 is the right answer for most laboratories. It handles cell culture, clinical microbiology and diagnostic work. You only need to look further if you use volatile toxic chemicals, which require a hard-ducted Type B2, or you work at containment level 4, which requires Class III.

Prices in our range run £6,365 to £14,661, and the specification that most affects both price and siting is whether the cabinet has single or double HEPA exhaust.


What is a biosafety cabinet?

A biosafety cabinet is an enclosed, ventilated workspace that protects the operator, the sample and the environment from exposure to infectious aerosols, using HEPA-filtered airflow and an inward air curtain at the open front.

Three things happen at once. Room air is drawn in through the front opening, forming a barrier that stops aerosols escaping toward the operator. HEPA-filtered air flows down over the work surface, keeping the sample clean. Exhaust air passes through a second HEPA filter before leaving the cabinet.

That combination is what separates a biosafety cabinet from every other enclosure in a lab. You will also see them called microbiological safety cabinets, biological safety cabinets, biohazard cabinets or Class II cabinets. These are the same equipment.

In the UK they should be manufactured and tested to BS EN 12469:2000, which sets minimum performance criteria and test procedures for operator, product and environmental protection.

Class I, Class II or Class III: which do I need?

Class II for almost everything. Class I where you need containment but not sample protection. Class III only for the highest-risk agents.


Class I

Class II

Class III

Protects operator

✔

✔

✔

Protects sample

✘

✔

✔

Protects environment

✔

✔

✔

Front

Open

Open, air curtain

Sealed, glove ports

Typical use

Dust and low-risk agent containment

Cell culture, clinical microbiology, diagnostics

BSL-4, highest-risk agents

In our range

✘

✔ 13 models

✘ specialist order

And the comparison people actually get wrong: a laminar flow cabinet offers no operator protection at all. Its airflow travels from the filter, across your work, and out toward your face. Excellent for sterile media, dangerous for anything infectious. If you are choosing between the two, read that guide alongside this one.


What does Type A2 mean, and when would I need B2?

Type A2 recirculates about 70% of its air and exhausts 30% through a HEPA filter. Type B2 exhausts 100% and must be hard-ducted to outside. Every cabinet in our range is Type A2, which covers the great majority of laboratory work.


The deciding factor is chemistry, not biology.

Choose Type A2 for cell culture, clinical and diagnostic microbiology, sterility testing and general Hazard Group 2 work. It can be used with trace quantities of volatile chemicals, and can be connected to building extract through a thimble or canopy connection that does not seal to the cabinet.

Choose Type B2 only when volatile toxic chemicals or radionuclides are used in more than trace amounts. Because it is hard-ducted and exhausts everything, installation cost and complexity rise substantially, and cabinet performance becomes dependent on the building's extract system.

A common and expensive mistake is specifying B2 "to be safe". If your work does not involve significant volatile chemistry, you are paying for ductwork you do not need and creating a dependency on the building services.


Single or double HEPA exhaust?

This is the specification that most affects containment assurance, and it is where our range genuinely splits.

A standard Class II Type A2 cabinet passes exhaust air through one HEPA filter. A double HEPA exhaust design passes it through two filters in series before the air returns to the room.


Choose double HEPA exhaust where the consequence of a filter failure is serious: clinical diagnostics, work with Hazard Group 3 organisms under a suitable risk assessment, or any environment where the cabinet exhausts into an occupied room rather than through building extract.


Single HEPA exhaust is appropriate for routine Hazard Group 2 work in a well-ventilated laboratory.

In our range the difference is visible in the model codes. The -D models are double HEPA exhaust; the -S models are single. Ask which you are being quoted, because the phrase "Class II Type A2" alone does not tell you.


Where should a biosafety cabinet be installed?

Away from doors, walkways and air-conditioning outlets, with clearance above for the filters.

A Class II cabinet depends on a stable inward air curtain at the front opening. Anything that disturbs room airflow can break that curtain and compromise containment, which is a safety issue rather than an inconvenience.

  • Site away from doors, high-traffic routes and any supply or extract diffuser

  • Keep clear space above the cabinet for filter access and exhaust

  • Do not site opposite another cabinet or a fume cupboard, where the two airflows can interfere

  • Confirm floor loading and access route before delivery. A 5 ft or 6 ft cabinet is heavy and will not go round a tight corner

  • Allow the cabinet to run before and after work to purge the chamber

For a Type A2 connected to building extract, use a thimble or canopy connection rather than a sealed duct, so that a failure of the building extract does not disturb cabinet airflow.


How often must it be tested?

Annually as a minimum, and after installation, relocation, filter change or repair. This one is not optional.

Testing to BS EN 12469 covers operator protection, product protection and cross-contamination protection, alongside airflow velocities and HEPA filter integrity. Where a cabinet is used for work under COSHH or containment regulations, the test record is the evidence that your control measure works.

Between tests:

  • Decontaminate the work surface before and after every session

  • Do not block the front or rear grilles. Blocking them is the most common cause of a failed containment test

  • Log and investigate any airflow alarm rather than silencing it

  • Plan for a HEPA change every few years, sooner in dusty or high-use environments

  • Arrange formaldehyde or vapour-phase decontamination before any filter change or relocation


Our ISO 17025 calibration and testing services cover annual cabinet validation alongside the rest of your equipment schedule.


Biosafety cabinets from LS Scientific

Thirteen Haier Biomedical Class II Type A2 models. Prices are current at the time of writing and include sale reductions.

X-Series, standard Class II Type A2

For basic cell biology, microbiology, biomedicine and biosafety laboratories.

Model

SKU

Width

Price

X-Series, touchscreen control panel

HR1800-IIA2-X

6 ft

£12,458.55 (35% off, was £19,167)

X-Series

HR1500-IIA2-X

5 ft

£14,661.35

X-Series

HR1200-IIA2-X

4 ft

£13,506.15

Worth knowing: the 6 ft touchscreen model is currently £2,200 cheaper than the 5 ft, because it is on a 35% clearance with limited stock. If a 6 ft cabinet suits your space, this is the best value in the range by a wide margin, and it will not last.


Intelligent Series, Class II Type A2

LED control panel, telescoping stand on most models, available with single or double HEPA exhaust.

Model

SKU

Configuration

Price

Intelligent Series, 5 ft

HR1500-IIA2

Stand

£10,450.00

Intelligent Series, single exhaust

HR1200-IIA2-S

Telescoping stand, single HEPA

£10,846.15

Intelligent Series, 4 ft

HR1200-IIA2

Telescoping stand, double HEPA

£9,578.85

Bench-mounted, 4 ft

HR1200-IIA2-D-NS

No stand, double HEPA

£9,673.85

Intelligent Series, 3 ft bench-mounted

HR900-IIA2-D-NS

No stand, double HEPA

£8,961.35

Intelligent Series, 3 ft

HR900-IIA2

Telescoping stand, single HEPA

£8,471.15

Compact, single-operator

HR700-IIA2

Telescoping stand, single HEPA

£6,365.00

The HR700 is the entry point at £6,365 and is designed for constrained spaces and single-person operation, including sampling stations and mobile laboratories.


Accessories and upgrades


Related equipment for a containment workflow: autoclaves for decontaminating waste before it leaves the lab, culture media and petri dishes, incubators, and PPE.


Tell us the organisms and the room and we will tell you the class, the type and the exhaust configuration. Talk to our technical team.


Frequently asked questions

What is the difference between a biosafety cabinet and a laminar flow cabinet? A biosafety cabinet protects the operator, the sample and the environment. A laminar flow cabinet protects only the sample and offers no operator protection, because its airflow travels toward the user. Never use a laminar flow cabinet with infectious material.

What does Class II Type A2 mean? Class II means it protects operator, product and environment. Type A2 means it recirculates roughly 70% of its air and exhausts 30% through a HEPA filter, and may be connected to building extract through a thimble rather than being hard-ducted.

When do I need a Type B2 instead of Type A2? Only when volatile toxic chemicals or radionuclides are used in more than trace quantities. Type B2 exhausts 100% of its air and must be hard-ducted to outside.

What is double HEPA exhaust and do I need it? Two HEPA filters in series on the exhaust rather than one. Worth specifying where a filter failure would be serious, or where the cabinet exhausts into an occupied room. Single exhaust is adequate for routine Hazard Group 2 work.

Does a biosafety cabinet need to be ducted? A Type A2 does not. It recirculates filtered air to the room and can optionally connect to building extract through a thimble. A Type B2 must be hard-ducted.

How often does a biosafety cabinet need testing? Annually as a minimum, and after installation, relocation, filter change or repair. Testing follows BS EN 12469 and covers operator, product and cross-contamination protection.

How much does a biosafety cabinet cost in the UK? Between £6,365 for a compact single-operator model and £14,661 for a 5 ft X-Series unit. Most laboratories buying a 4 ft Class II Type A2 should budget around £9,500 to £13,500.

Can I use a biosafety cabinet for chemical work? Only in trace quantities, and only in a Type A2 with appropriate risk assessment. A biosafety cabinet is not a substitute for a fume cupboard, because HEPA filters remove particles, not gases or vapours.


References and standards

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