Fume hood

A deduction or a hood (also digester or digestor, especially in Switzerland, chapel ) is an important component of scientific laboratories, especially in chemistry, and serves to ensure safe working and the protection of the experimenter.

Construction and testing of deductions are regulated in the European standard EN 14175.

Such a deduction is made from a solid wall enclosed, fire - and chemical-resistant work surface, a movable front panel ( depending on the design with moveable side windows ) and a suitable ventilation system, which serves to gases, dusts and aerosols that arise in experiments immediately suck out the air. Most prints are equipped with connections for electricity, natural gas, nitrogen and cooling water and drains.

The movable discs provide access to the work area and protect in the closed state, the laboratory and the work ends in an accident ( boiling retardation, uncontrolled reactions, fires and explosions smaller ) from splinters, splashing or spreading of fire.

To assess the functional ability of the extraction constant, flags or plastic wind wheels are mounted in front of the air shafts to make the airflow visible in older deductions; for newer devices, a control device is integrated into the trigger unit, which emits warning signals in case of low suction power. The optimum suction is only guaranteed if the windows closed, with a narrow opening between the front wheel and work surface must always be present.

Whether the use of a trigger is necessary, it appears usually from the respective Material Safety Data Sheet for hazardous substances used. Is the risk of fire, dust or gas can not be excluded, a deduction must be used in any case.

Deductions are sometimes confused with safety cabinets. However, safety cabinets provide as opposed to deductions only protection against particles and aerosols using filters. The filtered air is, however, returned directly to the laboratory, gases and vapors are not retained in their filters.