1.2.1
Alarm setpoint is a fixed or
adjustable setting at which the system will automatically indicate
an alarm. The FSS Code, chapter 16, limits the maximum alarm setpoint
to the equivalent of 30% of the lower flammable limit.
1.2.2
Calibration is the process
of confirming the accuracy of the detector readings by comparison
with a standard.
1.2.3
Detection time is the time
interval, measured in seconds, between the time a change in the gas
concentration occurs at the gas analysis unit, and the time the unit
registers a reading of 90% of the gas concentration, also known as
T(90).
1.2.4
Detector is the sensing element
which measures the gas concentration.
1.2.5
Extraction is the physical
removal of vapours from a space by means of a pump.
1.2.6
Extraction time is the time
interval, measured in seconds, between the time a gas sample enters
the gas sampling pipe and the time it reaches the gas analysis unit.
1.2.7
Gas analysis unit is the assembly
in which the detector is housed, along with any associated analysis
components.
1.2.8
Gas concentration is the amount
of gas or vapour being measured, as expressed in % LFL.
1.2.9
Lower flammable limit (LFL) is
the volume fraction of gas or vapour below which an explosive atmosphere
does not form. Also referred to as lower explosive limit (LEL).
1.2.10
Response time is the sum of
extraction time and detection time.
1.2.11
Sampling pipes are the means
by which gas is conveyed from the spaces being monitored to the gas
analysis unit, including any fittings, valves or filters.
1.2.12
Sampling point is the entrance
to a sampling pipe inside a ballast or void space.
1.2.13
Span calibration gas is a
gas mixture of known concentration used for calibration/adjustment
of the gas analysis unit.
1.2.14
System refers to the fixed
hydrocarbon gas detection system.
1.2.15
Zero calibration gas is a
gas which is free from flammable gases, used for calibration/adjustment
of the apparatus zero point.
1.2.16
Zero point is the gas concentration
at which the gas analysis unit registers zero.