Chapter 2
Cylinder and Components
34
SAFETY FIRS T
Edition 1 – December 2019
MSA G1 Classic Breathing Apparatus
Manual alarm activation
The alarm on the DSU can be manually activated if assistance is required by pushing
the MANUAL ALARM button.
Thermal sensor and alarm
The DSU is fitted with a thermal sensor. If this sensor gets too hot a thermal alarm will
activate. Activation of this alarm is a warning to the operator that the temperature has
exceeded the unit’s operating range and that the unit may not function correctly.
The thermal sensor and alarm feature is not an indicator of the safe
working environment for the operator, but is designed to protect the
equipment.
The operator must continue to assess the working environment through
situational awareness of fire behaviour.
If the internal temperature of the DSU exceeds the limit of the instrument, a two-tone
sound (Hi-Lo) is emitted every 2½ seconds while this condition persists.
Ambient temperature
This table summarises the ambient temperature.
Temperature
Duration
90°C
> 90 minutes
120°C
> 25 minutes
150°C
> 17 minutes
180°C
> 12 minutes
250°C
> 5 minutes
Battery alarm
When the remaining battery capacity is less than one hour, a red flashing status-LED
together with a short acoustic beep will activate. Operators are not to change the
batteries in the DSU. If this alarm is noticed the DSU must be returned to the
State PPE&C Management Centre with an attached fault report.
