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Biological hood

Laminar flow biological fume hoods

Laminar flow hoods are the most commonly used in biological laboratories; the characteristic of these hoods lies in the forced control of the air flow, which is separated into different and separate strands by means of specific perforated grilles positioned on the work surface or in the upper part of the compartment.
In this way, the cleanliness of the fluid veins is truly remarkable, allowing the almost total absence of internal turbulence; all this reduces the risks of dispersion of infectious agents.

The biological hoods, unlike chemical hoods, have more functions:

protect samples from mutual or external contamination;
protection of the operator;
protection of the laboratory site;

For all these characteristics just mentioned of the biological fume hood, regular maintenance and the control of its perfect functioning ensure both its regular functioning as a collective protective device (CPD) for the safety of the personnel working in it, and its prolonged functioning in order to protect cultures of microorganisms from possible sources of contamination.

Class I fume hoods

These hoods have a frontal opening, the operator is protected by the flow of air that is directed from the outside to the inside of the hood through the frontal opening; the environment is protected by the presence of a HEPA (High Efficiency Particulate Air) filter in the exhaust system, the biological agents that can be used are those with low.medium risk.

Class II hoods

These types of hoods are the most commonly used. Their function is to ensure the protection and safety of the operator working in them, of the surrounding environment and finally, of the material being handled.

They are equipped with a front opening, and have a vertical laminar flow positioned on the work surface that characterises them; also in this version of hood, the air that enters and exits is filtered through a HEPA (High Efficiency Particulate Air) filter. The protection of the operator is quite good, while that of the sample and the environment are excellent. The microorganisms that can be used are group 2-3.
CLASSE II biological fume hoods are called BIOHAZARDs, this designation is given by the National Federal Standard 49 (USA).

This type of biological fume hood has different subclasses, this subdivision is determined by the degree of air recirculation in the interior compartment.
- CLASS II type A hoods allow an internal recirculation of 70% of the sucked in volume, with 30% of this exhausted into the room;
- CLASS II type B1 hoods allow an internal recirculation of 30% of the sucked in volume, with 70% of this exhausted into the room;
- CLASS II type B2 hoods there is 100% exhausted air into the room;
- CLASS II type B3 hoods there is 100% exhausted air into the room.
Through the extraction of room air via the front grille, compensation is achieved, thus creating an air barrier that blocks the escape of contaminated gases.

All fume hoods described so far provide maximum control and protection over the samples handled.

Class III biological fume hoods

This type of fume hoods are equipped with a totally hermetic closure, the operation is done at negative pressure; two to several skirt gloves can be used to manipulate the biological products inside the hood. This type of fume hoods have a HEPA filter on the inlet air and another HEPS filter on the outlet air. This type of biological fume hoods allow total protection of both the biological samples, the environment and the worker. The microorganisms that can be used are group 4.

Regulatory references

Over the years, different countries have developed different technical standards to regulate safety standards for the design of scientific laboratories. The variety of regulations at a European level has led to the need to create one that is valid for all, and so the first Community regulation UNI EN 14175 was issued, which sets out the safety and performance requirements for all laboratory fume hoods marketed in the European Community.
In Italy, in addition to the European regulations, Legislative Decree 81 was issued to regulate the obligations that employers must fulfil.

These regulations are based on the following

From these regulations it can be deduced that the employer or the manager in charge has the obligation to plan systematic checks, but they also have the responsibility to supervise that the various checks that are carried out are done according to the criteria recognised by all the regulations.
Today, the procedures for checking the functionality of biohazard hoods are regulated by UNI EN 12469, which defines the performance requirements that biohazard hoods must have, as well as the instrumental procedures.

Useful links:

Biohazard hoods

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