Gas detection
Gas Detection History
Gas Detection History
First Gas Monitors
Canary in a cage
Canaries are more
susceptible than humans to
low oxygen, methane gas,
or CO gas.
A passed out canary
means a dangerous gas
situation.
Generally two canaries
used.
Gas Detection History
Flame Safety Lamp (Davey’s Lamp)
Invented by SirHumphry
Davey (of England) in 1815
Oil flame adjusted to specific
height in fresh air
Flame contained within a glass
sleeve and with a flame
arrestor
High flame means methane
gas present
Low flame means low oxygen
Gas Detection History
Catalytic Combustion (LEL) Sensor
Developed by Dr. Oliver
Johnson 1926-1927
Working for Standard Oil
Co. of CA (now Chevron)
Need was toprevent
explosions in storage tanks
on oil and gasoline tankers
Dr. Oliver Johnson
Gas Detection History
Catalytic Combustion (LEL) Sensor
Principle : Hot wire catalytic platinum
filament oxidizes flammable gases or
vapors at lower levels than they
would normally oxidize in air.
Oxidizing gases or vapors cause
increase in temperature of hot wires
which increases electricalresistance
of the wire.
Second not wire not in gas stream
used as a reference filament.
Resistance change measured with
W heatstone bridge to deflect a meter.
Gas Detection History
Catalytic Combustion (LEL) Sensor
First instrument Model A
demonstrated in 1926 using
2 jar method shown.
Only one Model A built, for
demonstration purposes.
Gas Detection History
Model B LELMonitor
1927 Introduction
First practical production
model of LEL meter (weighs 12 lb)
Approx. 100 units made
PG&E used for 50 years
2 meters: 1 for gas reading
& 1 for sensor voltage
(critical adjustment)
20 made by Dr. Johnson while at
Standard Oil
Called the “Standard Oil Electric Vapor Indicator”
Used hand aspirator to draw sample
Gas Detection History
Sensor forModel B
2 filaments in a glass tube
One tube sealed as the
reference element
Instrument remained outside
the hazardous area
Flame arrestor on sample
inlet prevented flashback into
tested space
Gas Detection History
Johnson-Williams Instruments
Formed in 1928, Palo Alto, CA
Started by Dr. Oliver Johnson &
Phil Williams
Recognized as the first
“Electronics” company in“Silicon Valley”
Trademarked “J-W Sniffer”
Manufactured 80 more of the
Model B J-W indicator
Dr. Oliver Johnson
Gas Detection History
J-W “Sniffer” Model C
1929
Smaller & lighter than Model B
Approx. 300 units built
Accepted by US Navy
Had flame arrestor approval
for acetylene use
Gas Detection History
MSA
1929/1930 Borrowed J-W Model C for 3 months
Initially indicated to J-W they may want to sell
Model C
Returned meter with letter; “Does not fit into
MSA marketing plans”
6 Months later MSA introduced their own LEL
meter with same characteristics as Model C
World’s second gas detection company
Gas Detection History
MSA Explosimeter Model 2A
1935 Introduction
MSA’s 2nd design
Popular rugged unit, still in
use today
Uses 8 D-cell batteries
Used unbalanced bridge
circuit (no reference
filament)
Gas Detection History
Interferometer
1925-1927
Dr. Uzumi Doi did initial
research in 1927 at the Institute
of Physical & Chemical
Research in Japan
Dr. Ziro Tsuji of the Institute
developed the first working
prototype
Developed to help prevent
explosions on oil tankers, and
in coal minesDr. Tsuji
Gas Detection History
Interferometer
Uses principle of light
diffraction in air to
indicate presence of
methane or gasoline
vapors
Light diffraction creates
visible fringe lines that
shift to indicate gas
concentration
Gas Detection History
Interferometer (Riken Keiki)
1935: 40 units sold to coal
mine in Hokkaido
1938: Dr Tsuji re-invented,
simplified,...
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