Basic Documentation

Siemens Industry, Inc. Page 5 of 6
Document No. 149- 976
 Automatic S
ash Closure Mechanisms–
Mechanisms may be added to fume hoods to
slowly close the sash after a pre-designated
period in which there is no sash movement.
Such devices typically incorporate appropriate
safety features to ensure against personal injury
and exerting excessive closing force on flexible
hoses, electrical cords, or other apparatus that
may extend into the sash opening. The use of
these mechanisms is dependent on individual
facilities and may not be suitable for every
instance.
Conclusion
This paper has presented a factual discussion on
the ramifications of implementing automatic face
velocity setback. In general, the application of an
automatic face velocity setback provision requires,
as a minimum, the assurance that room airflow
conditions meet very stringent requirements. In
addition, fume hood users must be well aware of the
need to keep all chemicals and apparatus well inside
of the fume hood sash and not to create harmful air
currents due to their movements within the
laboratory. Fume hood users must also be made
aware that automatic face velocity setback is not a
substitution for closing the sash whenever possible.
However, if the fume hood users maintain safe work
practices and keep fume hood sashes closed
whenever possible, they will maintain a safe work
environment and maximize the reduction of
ventilation energy without the need for face velocity
setback.