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-AS/NZS 2243.8
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Fume
Cupboards
A Brief Guide to Fume Cupboard Electrical Safety
Explosion Hazards
Electrical safety standard (AS/NZS 2430) defines areas of risk according
to the likely presence of an explosive gas/air mixture. The inside of
a fume cupboard, and the inside of all the duct, is defined to be a zone
1 (high) explosion risk. The space around the fume cupboard opening, extending
600mm in front and to both sides, right down to the floor, is defined
to be a zone 2 (moderate) explosion risk.
The standard requires that
electrical equipment (switches, power points, fans) shall not be fitted
in such hazard zones unless of suitable design e.g. explosion proof.
These designated zones apply
to all fume cupboards which do not comply in full with AS/NZS 2243.8:2001.
Compliant fume cupboards are re-classed as non-hazardous. Ordinary switches
and power points can then be used, in specified locations. The criteria
which achieve the non-hazardous qualification are:
- A warning label specifying
spill capacity in the fume cupboard
- A sump with raised front
lip to contain spills.
- Balanced air flow through
the open sash of at least 0.5m/sec average velocity.
- Continuous exhaust airflow
monitor.
- Isolation of power and
gas service outlets, (but not the fan, which must keep running). The
isolator(s) must need to be manually re-set, and must operate.........
- manually in the case
of an emergency (such as a chemical spill)
- automatically in the
event of inadequate airflow
- automatically in the
event of power failure
- automatically for at
least 1 minute after starting the fan (pre-purge)
- The fan must operate for
at least 20 minutes after the isolator operates (post-purge)
Wet Hazards
Switches and power points can never be fitted inside the fume chamber. New
Zealand Electrical Code of Practice for Electrical Installations in Damp
Areas (NZECP2:1993) restricts the location of switches and power outlets
in relation to sinks.
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