A combustible gas detector in the trade sense is a handheld instrument that responds to methane, propane, butane and a long list of other flammable vapors. This guide compares the models technicians actually carry, using manufacturer specifications, and says which features a homeowner can skip.
Tic Rate Rises
You Are Close
Mark the Joint
These are locating instruments for trades and serious DIY use, compared on gas coverage, alert modes, probe design, sensor replaceability and power from manufacturer documentation and owner feedback. No laboratory testing was carried out.
The gooseneck sniffer in most HVAC vans.
Tri-mode alerts and a field-replaceable sensor.
Dual-range sniffer at a mid-range price.
No pick matches that combination yet. Try a wider budget or a different measurement.
| Product | Gases (listing) | Probe | Alerts | Sensor / Range | Power | |
|---|---|---|---|---|---|---|
| UEi CD100A | Methane, LPG, butane, ammonia, acetone, jet fuel | 18-in gooseneck, tip light | Tic rate, LEDs | Range not stated | Battery | View |
| RIDGID CD-100 | Methane, propane, butane, ethanol, ammonia, hydrogen | 16-in flexible | Visual, audible, vibration | Replaceable; adjustable sensitivity | Battery | View |
| Klein ET120 | Combustible (methane basis) | 18-in gooseneck | 5 LEDs, 85 dB | approx. 50 to 10,000 ppm, two ranges | Battery | View |
| Amprobe GSD600 | Methane, propane | Flexible probe | Beep rate, 5 LED levels, earphone jack | LEDs at >40, >80, >160, >320, >640 ppm | Battery | View |
| TopTes PT760 | LPG, methane, ethane, propane, butane and more | 12-in telescopic, flashlight | Tone rate, screen color, %LEL | %LEL display | USB-C rechargeable | View |
| Klein ET190 | Combustible | Pen, pocket clip | LEDs, escalating tones | 50 to 2,000 ppm, two modes | Battery | View |
| Forensics Detectors | Natural gas, alcohols, acetone, gasoline, diesel, LPG and more | Handheld | Color LCD with temperature | Methane-calibrated; 7-year sensor life stated | Battery | View |
Gas lists are taken from each manufacturer's listing. Where a ppm range is not stated, consult the manual; do not assume parity with units that publish one.
Trade instruments differ on four points that consumer sniffers ignore:
Fuel gases are standard. Ammonia, hydrogen and solvents matter for refrigeration, battery rooms and industrial work.
A tic rate is fastest to read by ear; vibration is the only mode that works in a noisy plant room with hearing protection.
Semiconductor sensors wear out. A field-replaceable sensor keeps the instrument in service; a sealed one is a replacement purchase.
Ten to thirty seconds in clean air before every use. Rechargeable units save batteries but need a charger on the van.
A combustible gas detector responds to any flammable gas or vapor its sensor can oxidize: methane, propane, butane, hydrogen, alcohol vapor and more. A natural gas detector is the same sensor type packaged as a fixed alarm and calibrated for methane. In practice the term "combustible gas detector" usually means a handheld trade instrument.
Most show relative concentration as a tic rate, LEDs or bars. The TopTes PT760 and PT210S display a %LEL figure. For a calibrated %LEL reading with a certificate you need a multi-gas monitor with a catalytic sensor, which is a different instrument class.
The heated metal-oxide sensor changes resistance when any reducing gas touches it, which is what makes it sensitive and cheap and also why alcohol, solvents and exhaust trigger it. Zero it in clean air and interpret a reading by whether it follows the pipe.
Manufacturers quote sensor lives from about two to seven years depending on the model and exposure. Check the response with a known source, such as an unlit lighter, before each job; when it stops responding, replace the sensor or the unit.
The CD100A is the reference point for this category because so many technicians have carried one. UEi lists a wide gas coverage that includes ammonia and acetone as well as the fuel gases, which is why it turns up in refrigeration and boiler work as well as at furnaces.
The design is the classic one: an 18-inch gooseneck with a light at the tip for looking into a burner compartment or under a boiler, and a tic rate that speeds up as the sensor nears the source. Reading a tic rate takes a little practice but it is faster than watching LEDs when your eyes are on the fitting. UEi states a 10-second warm-up, shorter than the consumer units.
There is no numeric readout and no vibration alert, and the listing does not give a ppm range, so check the manual if you need a sensitivity figure for a report.
The CD-100 is the instrument to choose if the tool will live on a van. RIDGID's two practical advantages are the vibration alert, which lets you work in a noisy plant room or with hearing protection on and still know when the tip is near gas, and the field-replaceable sensor, which turns a worn-out detector into a ten-minute swap rather than a replacement purchase.
Coverage includes hydrogen and ethanol alongside the fuel gases, sensitivity is adjustable from a button, and the 16-inch probe is flexible enough for burner compartments. The housing is built for drops.
It costs the most here and the listing does not state a ppm range, so it is not the tool for a homeowner who needs a sniffer twice a year. For a technician the replaceable sensor pays for the difference.
The ET120 is the crossover model: trade brand, stated range, two sensitivity bands, but priced closer to the consumer sniffers than to the RIDGID. For a serious DIYer, a landlord or a plumber who does occasional gas work it covers the job.
Klein's two ranges are the key feature. In the high-sensitivity band (50 to 1,000 ppm) it finds faint weeps; switch to the low band (1,000 to 10,000 ppm) when a leak is strong enough to pin the LEDs, and the display becomes useful again for locating the joint. Self-zeroing at power-up is automatic.
What it lacks is a tip light, a vibration mode and a replaceable sensor. If those matter, the two instruments above are the step up.
Short answer: for HVAC and furnace service the UEi CD100A is the standard gooseneck sniffer and covers ammonia and acetone as well as fuel gases. If the tool lives on a van and works in noisy plant rooms, the RIDGID CD-100 adds vibration alerts and a sensor you can swap in the field. For a serious DIYer or occasional gas work, the Klein ET120 gives trade-brand build and two ranges without the trade price.
The phrase covers any instrument that senses flammable gases or vapors, but in the trades it means a handheld sniffer with a heated semiconductor sensor on a probe. The sensor responds to whatever reducing gas reaches it: methane and propane, but also butane, hydrogen, alcohols, acetone and ammonia. That breadth is why the same tool serves furnace, boiler, refrigeration and battery-room work, and it is why the instrument cannot tell you which gas it found. The combustible gas detector explainer covers the basics; gas detector sensor types compares semiconductor, catalytic and infrared sensors.
A homeowner checking appliance connectors twice a year does not need vibration alerts, ammonia coverage or a replaceable sensor. The Klein ET120 or a TopTes PT520A does the job, and the handheld gas leak detector guide is the better starting point. This page exists for people who use the instrument every week.
A tic rate or LED stack shows relative concentration at the tip, not an absolute value. Sweep slowly, note where the rate peaks, then back off and approach again from another side to confirm. Strong leaks pin a single-range unit within a foot; that is what the Klein’s low range and the RIDGID’s adjustable sensitivity are for. If you need a number, the %LEL figure on the PT760 is indicative; a calibrated reading comes from a multi-gas monitor with a catalytic bead sensor, which is a different tool for a different purpose. What LEL means on a gas detector explains the scale.
A sniffer finds the leak; it does not guard a room. Every gas-appliance service should also confirm the customer has a listed fixed alarm, and the main gas leak detector guide covers those. For the rest of the bag, from manometers to CO analyzers, see building a gas detection toolkit and choosing a gas detector for HVAC work.
Instruments were compared on manufacturer documentation: gases listed, probe length and features, alert modes, stated range or LED thresholds, sensor replaceability and power. Owner feedback was reviewed for sensor life and false triggering. We did not run laboratory tests and publish no sensitivity figures of our own. Amazon data supplies images, availability and links only.
No. A CO detector cannot sense natural gas, propane or methane, and a smoke detector cannot either. Only a combustible gas sensor responds to a fuel leak.
Read Guide→A gas leak detector senses unburned fuel before it can ignite; a CO detector senses the poison left by fuel that burned badly. Neither covers the other.
Read Guide→
Where to put a gas alarm in a kitchen so it catches a range leak without false alarms, and which plug-in and sniffer models fit.
Read Guide→Affiliate disclosure: Akermin earns a commission from qualifying Amazon purchases made through links on this page. This does not affect our picks, which are based on documented specifications and owner feedback. Learn more.