GMI Shipsurveyor - Toxic Gas and TWA Alarms; Toxic Alarms (e.g. CO)

4-3
ALARMS
4.1.3 TOXIC ALARMS (e.g. CO)
Two (2) instantaneous alarm levels (Hi and HiHi) are
congurable, each with different alarm indications, refer
to Fig. 4-1. Both are rising alarms, i.e. if the detected gas
concentration rises above the specic alarm level, the alarm
is triggered. All alarms are user congurable to meet the
needs of different companies.
Additionally, two (2) Time Weighted Average (TWA) alarm
levels (STEL and LTEL) are configurable with alarm
indications, refer to Fig. 4-1.
Two (2) TWA alarms are congurable for each toxic range
within the instrument.
Note: A Time Weighted Average (TWA) value is the mean
average gas level over a specic period. The Short
Term Exposure Limit (STEL) is 15 minutes and the
Long Term Exposure Limit (LTEL) is 8 hours. The time
weighted averages are averaged over a full 24 hour
period whether the instrument is ON or OFF. Such
averaging essentially makes the instrument single
user applicable.
The option is available to restart the averaging after
each instrument switch-off, thus allowing for multiple
user application.