The laminar flow hood vs fume hood question, and the fume hood vs laminar flow hood phrasing of the same confusion, answered by who is being protected: why a laminar flow cabinet blows filtered air over the work and therefore protects the product and not the operator, why a fume hood pulls air inward and does the opposite, why a laminar fume hood or laminar flow fume hood listing is usually one or the other rather than both, what an iso 5 laminar flow hood classification actually specifies about the air rather than about the cabinet, where walk in fume hoods and a polypropylene fume hood are chosen for size and chemical resistance, what a fume hood substitute or filtered fume hood can and cannot replace, and why the wrong choice here is a safety failure rather than an inefficiency

Choosing the enclosure

1. Answer who is protected before anything else. Product only means a clean air bench. Operator only means a fume hood. Both means a biological safety cabinet of the appropriate class, or an isolator. Nothing else about the specification matters until this is settled.
2. Read a classification as a property of the air. A cleanliness class describes particle counts in the working zone under defined conditions. It says nothing about containment, and a very clean bench can be entirely unsuitable for hazardous work.
3. Choose materials for the chemistry. Where strong acids or solvents are used, the cabinet material and the extract path have to tolerate them. A stainless enclosure and a polypropylene one are chosen for different chemistries.
4. Understand what a filtered enclosure replaces. A recirculating filtered enclosure removes particulates and, with the right media, some vapours. It does not remove everything, and the filter has a life that has to be monitored rather than assumed.
5. Certify on a schedule and act on the trend. Face velocity, containment and filter integrity are tested annually. A result that has been marginal for successive tests is telling you something about the system rather than about the test.

Direction of flow is the whole answer

Air moving out over the work protects the work. Air moving in protects the person. A cabinet that does both, by filtering the exhaust and maintaining inward flow at the opening, is a third design with its own classes.

Write the requirement as a sentence about who is protected, and the equipment category follows without argument.

Certification is a system test

Annual testing checks the enclosure in its installed environment, which includes the room's air balance and any nearby traffic. A cabinet moved or a door added changes the result.

Retest after any change to the room, not only on the annual schedule, and keep the certificates with the asset record.

Common questions

Can I use a clean air bench for cell culture with a pathogen?

No. It protects the culture and blows air at the operator. Work with an agent requiring containment belongs in a biological safety cabinet of the appropriate class.

What does an air cleanliness class mean?

A limit on particle counts in the working zone under stated conditions. It is a statement about cleanliness, not about containment, and the two are frequently conflated in purchasing.

Is a ductless enclosure a fume hood?

Only within limits. It filters rather than exhausts, the filter media have to match the chemistry, and the filter has a finite capacity that must be monitored. For many chemistries it is not an adequate substitute.

Browse by service class

• Compare Gene synthesis on advertised prices