N.2 – Microbiological Validation of Biohazard Cabinet and Laminar Flow Bench



Each laminar flow bench and Biohazard cabinet must be regularly tested and validated to control their performance. The purpose of the test is to identify breakage or irregularity of filters and/or alteration of the laminar flow with consequent turbulence and contaminated air introduced into the working area. The validation can be performed by company staff or entrusted to an external service organisation.


Starting up before testing

The supplier’s instructions must be followed and the operator should prepare the cabinet as follows:

– disinfect all inside surfaces

– adjust air flow by differential manometer

– free the working area from any lab material

– leave the cabinet in working condition for 12/24 hours.


Particles and “DOP” control

These tests are performed with the suitable instrumentation every 4/6 months.


Microbiological Control

The Microbiological Air Sampler is used to collect five samples in five minute time intervals as suggested:

The aspirating head of the air sampler should be positioned on a tripod, in horizontal position, at the front of the bench in connection with the edge of the working surface.

Operative conditions

The operator must perform all the requested actions in aseptic conditions, wearing mask and sterile gloves. The air sampler body must be disinfected by diluted isopropilic alcohol (or other suitable disinfectant).

Doors and windows of the laboratory should be closed and people should not walk dose to the cabinet to avoid air turbulence.

The aspirating head of the air sampler must be autoclaved at 121 °C for 20 minutes.

The nutritive media is “Trypticase Soy Agar” in triple packing sterilized by irradiation for use in sterile area. The volume of air to be sampled in each position is 1.0001itres (1m3). Incubation temperature is 37°C and incubation time is 48 hours.


Results evaluation

The cabinet is validated if only one Contact Plate out of five has no more than 1 C.F.U.


Visual Control

Filler, pre-filter, air ducts, and inside surfaces should be visually controlled to identify possible macro-defects.


Documentation for validation

The documents for validation must specify all the details indicated in the paragraph “Microbiological control”. Furthermore it should include:

– name and signature of the person responsible of the test company name and address (when applicable)

– suggested time for next testing

Action to be taken in case of unsuccessful validation

– check filter and pre-filter condition by differential manometer

– clean and disinfect surfaces, corners, grating

– check the integrity of the filter – repeat the test



USP chapter 1116 – Qualification Standard at 1 CFU.