australia:gasleak_detectors
Table of Contents
gas leak detectors
see also:
- I don't sell any of these nor do I receive any remuneration if you buy them, and I have not personally reviewed them, they are listed here to give you perspective
Introduction
- gas leak detectors come in a range of types:
- carbon monoxide detectors
- these are designed to detect CO local leaks from gas heaters, etc and differ from CO alarms which are designed to detect high levels of CO in a room
- combustible gas detectors (“LEL”)
- particularly used for finding natural gas or LPG leaks from fittings or pipes
- refrigerant gas detectors (“freon”/“halogen”/R22/R23/R134a/etc)
- designed to find leaks in air conditioner or fridge pipes or fittings
- dangerous air, combined gas detectors
- not designed specifically for gas leaks but to ascertain if the air in enclosed spaces are safe to enter without breathing apparatus
- usually detect CO, H2S, oxygen, combustible gas, and possibly CO2
carbon monoxide detectors
combustible gas detectors
- these detect a range of combustible gases but do not identify which gas it is
- they usually provide measures in either ppm or % LEL (lower explosive level)
- they usually take 30sec to warm up and need to be auto-calibrated during this period in clean air
- there are three main types of sensors:
- Catalytic Combustion Sensors:
- this is the most common device used in budget detectors
- these have a heated catalytic bead coated with a catalyst.
- when combustible gas contacts the bead, it reacts with oxygen causing flameless combustion and heating of the bead.
- this changes the bead's electrical resistance, measured by a Wheatstone bridge circuit.
- the resistance change correlates to gas concentration.
- this sensor type responds to many hydrocarbons but cannot distinguish gas types—it only measures total combustible gas concentration
- Infrared (IR) Sensors:
- these detect gases by measuring the absorption of infrared light at specific wavelengths characteristic to hydrocarbons in the gas sample.
- the gas absorbs some wavelengths, distorting the IR beam.
- by analyzing absorption spectra, some IR detectors can identify certain gas types or mixtures, giving more selectivity than catalytic sensors.
- Semiconductor Sensors:
- these sensors have semiconductor materials whose resistance changes when combustible gas molecules interact with the surface. They detect gas presence but have less specificity and are more influenced by environmental factors. They also do not identify gas types but respond generally to combustible gases.
- most are calibrated against a methane standard and may use correction factors to adjust for other gases
- coal gas “town gas”
- produced by destructive distillation (heating in the absence of air) of bituminous coal is an explosive mixture of hydrogen (50-60%), methane (20-35%), carbon monoxide (10-20%), and carbon dioxide (5-10%) and is the cause of coal mine explosions and has now been replaced by natural gas and methane for housing purposes.
- lower explosive level (LEL)
- the lowest concentration of a combustible or flammable gas or vapor in the air that can ignite or explode if an ignition source (such as a spark or flame) is present
- methane (natural gas) has an LEL of about 5%, meaning methane concentrations below 5% by volume in the air are too lean to ignite
- propane has a LEL of 2.1% by volume
- n-Butane / iso-butane has a LEL of 1.6-1.9% by volume
- petrol fumes have a LEL of 1.4% by volume
- ethanol vapour has a LEL of 3.3% by volume
- hydrogen has an LEL of 4% by volume
- coal gas has an LEL of 4-5% by volume
- gas detectors display gas concentration as a percentage of the LEL for that gas detected
- thus, if it displays 5% LEL and the gas is methane then the concentration of methane by volume is 5% x 5% = 0.05 x 0.05 = 0.25% by volume
- NB. to allow humans to smell propane, butane, and natural gas, odorants are added to it
- humans can first smell the odorant added to propane when propane is at 0.15% to 2% by volume (range is due to variation in smell between humans), but most can smell this by 20% LEL, and most can smell butane by 0.12% concentration by volume (~7% LEL), and most can smell natural gas at 20% LEL
- DO NOT use a naked flame such as a match to detect a gas leak - it may cause an explosion!
- you can use soapy detergent water sprayed onto a gas fitting to visually see a leak
examples
- Habotest HT601A/B
- Catalytic Combustion Sensor
- Plus model has a color screen and rechargeable battery
- A model has lower accuracy (+/- 30%) and reduced range 50-1000ppm
- B model has +/- 10% accuracy for methane and range 0～9999ppm / 0.00～20.00% LEL
- detects Acetone, Acetylene, Alcohol, Ammonia, Benzene, Butane, Ethanol, Ethylene, Oxide, Gasoline, Hexane, Hydrogen, Methane, Naphtha, Natural Gas, Paint Thinners, Propane, Solvents, and more.
refrigerant gas detectors
- they usually take 30sec to warm up and need to be auto-calibrated during this period in clean air
examples
- Mestek HD02/HD02C
- the C model has a color screen and rechargeable battery
- high temp, low pressure refrigerants: R11, R113, R114, R21
- med temp, med pressure refrigerants: R12, R22, R717, R142, R502
- low temp high pressure refrigerants: R13, R14, R503, alkanes, alkenes
- hydroflourocarbons (HFCs)
- hydrochloroflourocarbons (HCFCs)
- chloroflourocarbons (CFCs)
- perflourocarbons (PFCs)
- unsaturated organic compounds containing H,F and C (HFOs)
- ammonia refrigerants - R717
dangerous air, combined gas detectors
- not designed specifically for gas leaks but to ascertain if the air in enclosed spaces are safe to enter without breathing apparatus
- usually detect CO, H2S, oxygen, combustible gas, and possibly CO2
examples
- GVDA ST8904
- detects CO, H2S, oxygen, combustible gas LEL
- GOYOJO GAS4
- detects CO, H2S, oxygen, combustible gas LEL
- HoldPeak HP-9000A
- detects CO, H2S, oxygen, combustible gas LEL
- HoldPeak HP-9000B
- detects ammonia (NH3
australia/gasleak_detectors.txt · Last modified: 2025/10/02 05:37 by gary1