Testing the conformity of a biosafety cabinet
Correct laminar flow in the work chamber Personnel, environment, and product protection in microbiological safety cabinet is provided with various types of barriers, such as case frame, filters, and air flow.
Barrier’s function is to prevent or minimize microorganisms’ or aerosol’s movement between adjacent areas. Case frame and filters are rather obvious barriers by its functionality and visibility; however air flow is protection that is nearly intangible and absolutely invisible, importance of which is often undervalued.
In the meanwhile there are areas in the cabinet construction where airflow is the only possible way of protection of an operator, product, and environment. Such areas, for instance, are a working opening through which operator performs manipulations and an operating area in the cabinet.
Product located in an operating area must be protected from cross-contamination. For that purpose filtered air is supplied in the cabinet’s chamber as a laminar flow. Thin air streams flow in one direction without interfusing and prevent aerosol particles from chaotic movement initiating contamination.
Airflow visualization in a work chamber of the cabinet using chemically created smoke is a testing method for defining whether the air flow is laminar. To perform such test unassisted, one can use electronic cigarette, steam generator or other harmless source of smoke.
In our video airflow direction at different spots in the cabinet’s work chamber is clearly visible.
Laminar downflow descends to the table top without whirls and interfusions and then it forcedly gets sucked in the perforation holes for further filtering.
By EN 12469:2000 air flow in a work chamber of class II microbiological safety cabinet must be just as described to provide reliable protection of a product from cross contamination.
Visualization of airflow incoming through the operating opening.
Creation of downward laminar airflow inside the cabinet and of an air curtain in the operating opening is a conventional way to provide protective features of the microbiological safety cabinet class II.
Air curtain in its wide sense is effective way of separation of adjacent areas from one another to maintain certain characteristics in isolated content, such as temperature, humidity, or as in case with microbiological safety cabinet, air cleanliness.
Protective feature of the air curtain involves firstly in isolation of the work chamber with clean filtered air from external impurities, secondly in retention of pathogenic microorganisms within the cabinet and prevention of their discharge into external environment, including towards the operator.
Air curtain in the operating opening of the cabinet is created when external air is forcedly sucked in through the operating opening with a certain mean flow velocity. Stability of velocity in this case is a key factor. If velocity value is below required, air flow won’t manage separation of the work chamber from external environment since its transmittance will be too high. If the velocity is higher than required, external contaminated air will easily get into the work chamber of the cabinet.
We offer you to watch smoke visualization of the air curtain in an operating opening of the microbiological safety cabinet class II.* Please note that smoke stream flows with an incoming airflow directly into the perforation holes of the front grille without whirls and without appearance in the work chamber of the cabinet. Such smoke flow movement proves that air balance is optimal in the operating opening and guarantees that protective properties of the cabinet are fulfilled. Average inflow velocity in this case is 0.47 m/s.
Measurement of an average inflow velocity.
Inflow velocity value is measured with a special device. Visualization with a smoke only helps to make sure that airflow direction and distribution is correct.
Average inflow velocity in this case is 0.47 m/s.