FIRE
R M LD
FIRE
R M LD
Operator’s Manual
25
GAS LASER
Doc No. 16162 Rev A, GAS LASER Operator Manual
© 2021 Teledyne Gas Measurement Instruments Ltd. All rights reserved.
WARNING - The Gas Laser is
capable of scanning through
windows to possibly detect methane
gas. However, scanning through
windows is not guaranteed. False
positives and negatives may occur.
AVERTISSEMENT : Le Gas Laser
est capable de balayer les fenêtres
pour éventuellement détecter du
méthane. Cependant, le balayage
des fenêtres n’est pas garanti. Des
faux positifs et des faux négatifs
peuvent être obtenus.
WARNING
1
Laser Beam
Is Transmitt
ed
2
Plume Absorbs
Some Laser
3
Some Laser
Passes Through
6
Remaining Laser R
eturns t
o
Gas Laser and Is Measur
ed
4
Laser
Reflects Back
5
Plume Absorbs
Some Laser
How Does the Gas Laser Measure Gas?
The Gas Laser uses infrared
(IR) laser technology known
as Tunable Diode Laser
Absorption Spectroscopy
(TDLAS).
TDLAS enables the Operator to
safely scan:
- Hard to reach areas
- Plumes up to 100’ away
(actual distance may vary
due to surface condition)
- Through windows
Infrared beam width is about 22” at 100 feet. It is important to note that the laser
beam “footprint” width increases as the distance increases. This is why it is much
easier to detect natural gas from a distance of 10 to 15 feet and beyond.
NOTICE: There is always a small
amount of methane in the air.
This natural methane background
is also measured by the Gas Laser.
The PPM-M reading will then
increase as the scanning distance
increases.
NOTICE: The nature of a gas plume
is highly variable. The above/right
illustrations are intended to convey
the basic theory. Some leaks may
have a high surface concentration
with little to no measurable plume
above the surface.
NOTICE
0.5 M
1000 PPM
2 M
1000 PPM X 0
.5 M = 500 PPM-M
20 PPM X 2 M = 40 PPM-M
+ background le
vel of 15 PPM-M = 55 PPM-M
20 PPM
A
B
a) Gas cloud of 1000 PPM is about ½ meter in width (the distance the
infrared beam passes through the plume).
Gas Laser
measures 500 PPM-M.
b) Average concentration of gas cloud is 20 PPM and is about
two (2) meter in width.
Gas Laser
measures 40 PPM-M,
plus 15 PPM-M background level, displaying a total value of 55 PPM-M.
A
B
100’
50’
25’
75’
22”
When the laser passes through a gas plume, a portion of the light is
absorbed by methane, while some of the light is reflected back to the
Gas Laser. The reflected light is collected and processed so the Gas Laser
can report methane concentrations in parts-per-million-meter or PPM-M.
AVERTISSEMENT
