Appendix 6. Ventilated work station (VWS) and bio-safety cabinet (BSC)

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    6.1 Ventilated workstation (VWS)

    The VWS provides a safe work environment while preparing sputum smears for AFB staining and Xpert MTB/RIF. It is used when adequate natural ventilation cannot be achieved. Designed to be placed over a bench, it is constituted by a rectangular box ducted to the outside, where the duct is connected to an extraction fan.
    VWS are used without filter and do not provide product protection. They should never be used for preparing cultures.

    6.2 Class II BSC

    A Class II BSC protects not only the operator and the environment, but also the material being manipulated inside the cabinet.
    The room air and the air circulating within the cabinet are drawn by a downward flowing current through a grate then, through a HEPA filter, which protects both the operator and the product. The air exiting the cabinet is filtered through a HEPA filter to protect the environment.
    Class II BSCs are required for performing cultures.


    • Class I BSCs cannot be used for performing cultures and VWS are sufficient for preparing samples for microscopy and tests Xpert MTB/RIF. Therefore, their use is not recommended in this manual.
    • Class III BSCs are generally not used for TB.