CEN-PAQ
4
The high visibility waistcoat MUST NOT
be used in potentially explosive or
flammable atmospheres.
The waistcoat is designed to fit a wide
range of body sizes with the minimum of
adjustment.
The alloy steel cylinder has a brass
cylinder valve with a handwheel. A safety
lock on the handwheel prevents
accidental valve closure. The cylinder is
retained in the pouch by a tough, dual
action buckle.
2.1 PNEUMATICS
High-pressure air from the cylinder is
connected through the cylinder valve and
a length of high-pressure hose to a
pressure reducer. A sintered filter in the
connector prevents the ingress of dirt and
debris.
A high-pressure hose from the reducer
supplies air to the shoulder-mounted
pressure gauge and warning whistle
assembly. The gauge dial has photo-
luminescent markings to improve low-
light legibility. The gauge is protected by
means of a rubber shroud.
The warning whistle operates at 68 bar,
when there is at least 200 litres of air left
in the cylinder, giving a warning period of
5 minutes when consumed at 40
litres/minute (please refer to Section 1.4 -
Apparatus Duration for further details).
The high-pressure hose has a minimum
burst pressure of 800 bar.
2.2 REDUCER
The pressure reducer operates on a self-
regulating, spring-loaded piston principle
that is completely automatic in operation
and requires no adjustment.
A restrictor within the reducer body
prevents air loss in excess of 25 litres per
minute should the gauge, whistle or hose
become damaged.
A pressure relief valve prevents over-
pressurisation of the medium pressure
breathing circuit.
An outlet pressure of between 5.0 and
11.0 bar from the reducer is supplied to
the facemask-mounted demand valve.
2.3 DEMAND VALVE
Air from the reducer is connected through
a reinforced chlorinated polyethylene
hose to the facemask-mounted DV,
which regulates the air supplied to the
wearer.
The DV operates in conjunction with the
facemask spring-loaded exhale valve to
maintain a positive pressure within the
facemask.
The DV has a servo-assisted tilting
diaphragm mechanism that responds to
pressure changes within the facemask to
regulate the flow of air to the mask,
ensuring that pressure within the mask
remains safely above ambient.
The DV has a reset button that enables
wearers to close the airflow through the
DV, permitting the facemask to be
removed during test procedures and at
the end of a task, without loss of cylinder
air.
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