Let me put the safety line first, because everything else on this page sits underneath it. If you smell gas, or any detector on this page goes off, you ring the National Gas Emergency line on 0800 111 999, free, staffed around the clock. Open the windows, don’t operate light switches or anything electrical, put the cigarette out, turn the gas off at the meter if you can safely reach it, and get out. Then a Gas Safe registered engineer finds and fixes the fault. Nothing you can buy for £30 — or £300 — changes any of that. A gas detector is triage. It tells you a question needs asking urgently; it never answers it.
With that said: I walk into a lot of houses, and the faint smell of gas in a meter cupboard, behind an elderly hob, or around a disused fire in a chimney breast is not rare. Every EPC visit starts at the meter and ends at the boiler; building surveys take me past pipework nobody has looked at since the appliance it fed was scrapped. The smell — strictly, the mercaptan odorant added so we can smell an otherwise odourless gas — is a remarkably good detector in its own right, but it can’t localise. A handheld sniffer can: probe along a pipe run and the tick-rate rises as you approach the source, exactly like a Geiger counter. That is the entire trick, and it is genuinely useful.
Two families of kit, then. Handheld sniffers for finding where a smell is coming from, and fixed alarms — plug-in or wall-mounted, the relevant standard is EN 50194 — that sit there for years waiting to shout. Both have a place in a house with gas appliances, an LPG-fed park home or a caravan. Neither is a substitute for the tightness test a Gas Safe engineer performs with a manometer, and it’s worth understanding why before you spend anything.
The one I’d buy
TopTes PT210S
The sensible middle of the consumer market: a pen-format combustible-gas sniffer with a detachable 10cm flexible probe, adjustable high/low sensitivity, and a screen that reports leak severity as a two-digit %LEL figure alongside a rising bar graph and audible tick-rate. Owner feedback is consistent that it does the one job that matters — the ticking speeds up as you close in on a joint that’s weeping.
Typically £25–£35
Check price on AmazonHow I judge a gas leak detector
Tick-rate first. The useful output of a sniffer is not a number, it’s a rate of change. You sweep the probe along the pipe, around each compression fitting, across the meter connections, and listen for the clicks accelerating. A detector with a clear, fast-responding audible scale beats one with a digital readout every time, because in a cupboard you’re watching the probe, not the screen.
A probe that reaches. Leaks live in awkward places: behind the hob, at the back of the meter box, under the boiler, at the restrictor elbow nobody has touched in twenty years. A flexible gooseneck or extendable probe is worth more than any spec-sheet sensitivity figure, because the sensor has to get within centimetres of the escape to catch it.
Honest about cross-sensitivity. Consumer sniffers use a heated semiconductor sensor that responds to more or less anything combustible — methane, propane, butane, but also solvents, deodorant, fresh paint, white spirit and last night’s bleach. A good unit says so in the manual and gives you a sensitivity control to work around it. A bad one prints “natural gas detector” on the box and lets you panic over hairspray.
Warm-up and zeroing. Semiconductor sensors need 30–60 seconds to heat up and settle, and they should be zeroed in clean air — outside, not in the room you suspect. A detector that lets you start it in fresh air and carry it in gives meaningful readings; one switched on next to the hob tells you nothing.
For fixed alarms: the standard and the siting. Domestic gas alarms should be built to EN 50194 and sited according to which gas they’re watching for. Natural gas is lighter than air, so the alarm goes high, near the ceiling, in the room with the appliance. LPG is heavier than air and pools at floor level, so an LPG alarm goes low. A plug-in unit at socket height is a compromise for methane and roughly right for LPG — think about which fuel you actually have before you buy.
The comparison
| Model | Format | Probe / siting | Typical price | Best for | |
|---|---|---|---|---|---|
| TopTes PT210S | Handheld sniffer | 10cm flexible probe | ~£30 | Home checks — the sensible default | View |
| Amprobe GSD600 | Trade sniffer | Long steel gooseneck | ~£250 | Professional tracing, methane & propane ppm | View |
| TopTes PT520A | Handheld sniffer | 43.5cm gooseneck | ~£40 | Reaching behind hobs and into meter boxes | View |
| TopTes PT199 | Pen sniffer | Fixed tip | ~£20 | Best on a budget | View |
| Neoteck gas leak detector | Pen sniffer | Fixed tip | ~£18 | The budget alternative | View |
| D MODUN plug-in alarm | Fixed alarm | Plugs into a 3-pin socket | ~£17 | Always-on methane/LPG alarm | View |
| Arctic Hayes PH020 spray | Leak detection fluid | Spray on the joint | ~£8 | Confirming a suspect fitting, bubbles don’t lie | View |
The picks in detail
TopTes PT210S
Best overall — the sensible home sniffer, and my top pick above
TopTes has quietly become the default name in consumer gas sniffers, and the PT210S is the one I’d point a homeowner at. The spec covers what matters: a semiconductor sensor with high and low sensitivity modes, a two-digit %LEL severity readout with a bar graph and an accelerating tick, and a short detachable flexible probe that gets behind a hob without dismantling anything. It runs on two AAA batteries you can buy in the village shop, and the published feedback is consistent on the core behaviour — quiet in clean air, unambiguous next to an unlit burner ring.
Its limits are the limits of the class: it responds to any combustible vapour, so zero it outdoors and expect it to notice solvents. Used as a locator for a smell you already suspect, it earns its £30.
For
- Clear tick-rate plus bar graph — built for localisation
- Flexible probe reaches the awkward 90 per cent of joints
- AAA batteries, sensible price, adjustable sensitivity
Against
- Reacts to all combustible vapours, not just gas
- %LEL reading is a severity indicator, not a calibrated measurement
Typically £25–£35
Check price on AmazonAmprobe GSD600
Best professional pick — the trade sniffer with a calibrated scale
Amprobe is a proper test-instrument firm (the same stable as Fluke), and the GSD600 is what a trade sniffer looks like: a long armoured gooseneck, a specified detection scale for methane and propane from 40 ppm up to 640 ppm on an LED ladder, and build intended for a van rather than a kitchen drawer. This is the class of instrument a heating engineer traces a weep with before soaping the suspect joint. Published feedback praises the response speed and probe reach; the recurring gripe is the price. Should a homeowner buy one? Mostly no — the PT210S does the triage job for an eighth of the money. But if you manage properties or want the instrument the professionals actually carry, this is the one on this page.
For
- Specified ppm scale for methane and propane, not a vague bar
- Long steel gooseneck holds its shape in awkward voids
- Test-instrument pedigree and build
Against
- Serious money for occasional domestic use
- Still a locator — it does not certify a system tight
Typically £220–£270
Check price on AmazonTopTes PT520A
Best reach — the long gooseneck for meter boxes and behind appliances
The step up from the PT210S buys you one thing above all: a 43.5cm flexible gooseneck, which is the difference between waving a pen in the general direction of a boiler and actually getting the sensor to the union at the back of it. The PT520A adds a colour display with three sensitivity levels and the same accelerating audio tick, still on ordinary AAA batteries. For checking a floor-standing boiler, the far side of a meter box, or pipework crossing a suspended timber floor from the access hatch, the reach is worth the extra tenner over the pen formats.
For
- 43.5cm gooseneck — the sensor goes where the leak is
- Three sensitivity levels tame false alarms in solvent-rich rooms
- Clear display readable in a dark cupboard
Against
- Bulkier than a pen — less likely to live in a kitchen drawer
- Same semiconductor cross-sensitivity as every consumer unit
Typically £35–£50
Check price on AmazonTopTes PT199
Best on a budget — the £20 pen that does the essentials
The PT199 is the stripped-back version of the same idea: pen format, fixed sensor tip, audible and visual alarm that quickens as concentration rises, two AAA batteries, pocket clip. No probe, no screen worth the name — you’re buying the tick and a row of LEDs. For an annual sniff around the hob flexible, the meter connections and the boiler union, that is genuinely all you need, and owner feedback is that it does exactly this without drama. The fixed tip means some contortion at the back of appliances; if that annoys you, the PT210S’s probe is the answer.
For
- Cheap enough to buy alongside a plug-in alarm
- Simple tick-and-LED output — nothing to misread
- Genuinely pocketable
Against
- No probe — awkward behind hobs and in meter boxes
- Coarser sensitivity control than its bigger siblings
Typically £18–£25
Check price on AmazonNeoteck gas leak detector
The budget alternative — same class, second opinion
Neoteck’s pen sniffer is the perennial other name in the £15–£20 bracket and functionally the PT199’s twin: semiconductor sensor, audible and visual alarm, backlit bar display, AAA power. Published feedback follows the pattern of the whole budget class — fine at the “is something here?” job, occasional units that alarm at nothing, no calibration or spares story. I list it because it’s frequently a few pounds cheaper than the TopTes and stock of these things comes and goes; treat whichever is available as interchangeable.
For
- Often the cheapest credible sniffer on the page
- Simple, pocketable, backlit for dark cupboards
Against
- Quality control is more variable at this price
- No probe, no calibration, no spares
Typically £15–£22
Check price on AmazonD MODUN plug-in gas alarm
Best always-on cover — the plug-in alarm for the kitchen with gas appliances
A sniffer only works when someone is holding it; an alarm works at three in the morning. This D MODUN unit plugs into a standard UK 3-pin socket, watches for natural gas, LPG and town gas, and sounds a claimed 85 dB siren. It is the always-on complement to any sniffer above, particularly in a kitchen with an ageing gas cooker or a house that stands empty between tenancies. Siting caveat: a socket-height unit is a compromise for methane, which collects at the ceiling — if your risk is mains gas, use the highest socket you have, and test the alarm monthly like a smoke alarm.
For
- On duty continuously, asleep or away
- Covers methane and LPG in one unit
- Cheap enough for kitchen plus boiler room
Against
- Socket height is rarely the ideal height for methane
- Budget brand — replace it within the sensor life on the leaflet, and test it monthly
Typically £15–£20
Check price on AmazonArctic Hayes PH020 leak detector spray
The confirmation tool — because bubbles don’t have false positives
The oldest gas-tracing method in the book, in an aerosol: a foaming solution to EN 14291 that you spray on a suspect joint, and if gas is escaping it blows bubbles. This is what your sniffer’s finding gets checked against. Where an electronic sensor will alarm at deodorant, a bubble at a compression fitting is gas leaving the pipe, full stop. Arctic Hayes is a trade brand, the can costs less than a sandwich meal, and it works on gas, air and refrigeration lines alike. It is also the only thing on this page that never needs batteries.
For
- Effectively zero false positives at a visible joint
- EN 14291 fluid, non-corrosive, trade standard
- Under a tenner, lasts years
Against
- Only works where you can see and reach the fitting
- Finds nothing — it confirms what a sniffer or your nose found
Typically £5–£10
Check price on AmazonWhat actually matters — and what doesn’t
A detector is triage, not certification. Here is the hard limit of everything above. A consumer detector can conclude one thing: combustible gas is present near this point, above this sensitivity threshold, right now. It cannot conclude that a system is sound. The only way to establish that is a let-by and tightness test — the installation pressurised and watched on a manometer for drop — performed by a Gas Safe registered engineer. A sniffer that stays silent along an accessible pipe run says nothing about the joint buried in the screed. Use the tools on this page to decide how urgently to pick up the phone, never to decide not to.
Know your gas, because it decides everything. Mains natural gas is mostly methane, lighter than air: it rises, collects at ceilings, and a fixed alarm belongs high. LPG — propane in the garden tank, butane in the caravan cylinder locker — is heavier than air: it sinks, pools at floor level and in ducts, and its alarm belongs within about 30cm of the floor. A detector positioned for the wrong gas is furniture. This matters particularly in park homes and caravans, which I see plenty of through RdSAP work — they run on LPG, and the alarm siting is the opposite of a house on mains gas.
False positives are a feature, not a fault. Semiconductor sensors respond to hydrogen, alcohol, solvents and aerosols as enthusiastically as methane. So: zero the unit in outdoor air, keep it away from fresh paint and cleaning sprays, and treat any alarm as real until shown otherwise. The escalation path for a positive is the spray can — bubbles at a reachable joint — and 0800 111 999. It is never “tighten the nut yourself and see if the ticking stops”. DIY work on gas fittings is illegal unless you are competent within the meaning of the Gas Safety (Installation and Use) Regulations, and the practical meaning of that is Gas Safe registration.
What the marketing pushes that you can skip. Wi-Fi apps on £20 alarms, “ppm accuracy” claims on pen sniffers with no calibration certificate or service path, and combined smoke/CO/gas gadgets that do three jobs to no standard at all. A carbon monoxide alarm is a different instrument for a different hazard (EN 50291, and after the 2022 regulations, a legal requirement in rented rooms with fixed combustion appliances) — buy one, but buy it separately. Spend the gas-detector money on probe reach and a clear tick, and put the change towards the annual boiler service that prevents most of this in the first place.
Questions I get asked
What should I do if my gas detector goes off? Treat it as gas until proven otherwise. Stop using anything with a flame or a switch — no lights on or off, no phones inside the property — open doors and windows, turn the supply off at the emergency control valve by the meter if it’s safe to reach, get everyone out and ring 0800 111 999 from outside. If the property runs on LPG, your cylinder or tank supplier will also have an emergency line on the paperwork. Do not go back in to check whether the alarm has stopped.
Where should I fit a natural gas detector? In the room where the appliance lives, high on the wall or ceiling — methane rises — typically within about 30cm of the ceiling, above door and window height, a metre or more from the appliance, and not directly over a hob or sink where fumes and steam cause nuisance alarms. LPG is the mirror image: low, within about 30cm of the floor. Look for EN 50194 on the box, and remember the sensor has a stated service life — typically five years or so — after which the unit is replaced, not trusted.
Can a gas leak detector detect carbon monoxide? The units on this page, no — and this catches people out constantly. A combustible-gas detector looks for unburnt fuel escaping from pipework; a CO alarm looks for the poison produced when fuel burns badly in a faulty or unserviced appliance. They are different sensors to different standards (EN 50194 versus EN 50291), and a house with gas appliances arguably needs the CO alarm more, since carbon monoxide has no odorant to warn you. Buy both; don’t buy one gadget claiming to be both for £15.
How do I check for a gas leak at home? Your nose is the first instrument — the odorant is added precisely so an escape announces itself. If you have a persistent faint smell, a smart meter or a stopped gas clock can offer a clue (all appliances off, and the meter still creeping, is a bad sign — a test a Gas Safe engineer will do properly with a manometer). A sniffer from this page will localise the smell to a joint, and leak spray will confirm it. And then it is 0800 111 999 and an engineer — a detector result, however convincing, is the beginning of that phone call, not a substitute for it.
If the reason you’re reading this is a property you’re buying with elderly gas installations, that’s the day job. The practice does building surveys that flag exactly this sort of thing for specialist investigation, and EPCs where the state of the heating system is half the story — get in touch. Inspection kit for the voids the pipework runs through is covered in the borescope guide, and there are more field-kit guides if you’re building out the toolbag.
Small print. This guide is general information, not gas safety advice for your property. If you smell gas or suspect a leak, call the National Gas Emergency line on 0800 111 999 and use a Gas Safe registered engineer; work on gas fittings is not a DIY job. Prices are indicative, move constantly and are checked at the time of writing; the linked page always shows the current price. As an Amazon Associate I earn from qualifying purchases.