Short answer: If you smell gas in the UK, deal with the emergency before looking for a detector. Do not smoke or light matches, and do not turn electrical switches on or off. Open doors and windows if safe, turn off the gas at the meter control handle if you know where it is and can do so safely, leave the area and call the National Gas Emergency Service on 0800 111 999. A handheld combustible detector such as the HT601B+ is not a substitute for that response. It is a later tracing aid at most, and it does not certify an appliance or repair.

Key takeaways

  • Call 0800 111 999 and follow National Gas emergency advice when gas is smelled or a leak is suspected.
  • Do not use a handheld detector to decide whether an active gas smell is safe to ignore.
  • After the emergency, keep combustible-gas tracing, CO protection and Gas Safe repair as separate tasks.

Emergency action comes first

National Gas lists the immediate controls: no smoking or matches, no switching electrical equipment on or off, open doors and windows, turn off the meter control handle unless the meter is in a cellar, and call 0800 111 999. HSE gives the same core direction to call the emergency freephone, ventilate and shut off the gas supply at the meter control valve if known.

A detector reading cannot safely replace those actions. If anyone feels unwell, leaves the property or is told to evacuate, do not return to continue testing until the responsible service says it is safe.

SituationFirst response
Smell of gas or suspected leakFollow National Gas emergency guidance and call 0800 111 999.
Possible unsafe gas applianceStop using it and arrange a Gas Safe registered engineer.
Possible CO exposureTreat it as a separate health risk; CO has no smell and needs appropriate protection.

What not to do with a sniffer

Do not switch on the HT601B+, plug in a charger, move a suspected leaking fitting or search a closed cupboard if doing so could create an ignition source or delay evacuation. The product page's visual and audible alarms do not turn the instrument into an emergency service or a certified domestic alarm.

The page documents 0-9999 ppm and 0-20% LEL displays, but not accuracy, response time, alarm thresholds, gas-specific compatibility or hazardous-area approval. Manufacturer does not specify those emergency-use properties.

After the emergency is controlled

Only after the supply and appliance have been dealt with by the responsible service should a later accessible tracing task be considered. HSE says an appliance suspected unsafe must not be used until checked by a Gas Safe registered engineer. A sniffer may help a qualified workflow find a point of interest, but it does not shorten the repair or verification process.

Keep carbon monoxide separate. HSE describes CO as colourless, odourless, tasteless and poisonous, so the absence of a fuel-gas smell is not evidence that there is no CO risk.

  1. Handle the gas emergency and wait for the responsible service or engineer to make the situation safe.
  2. Define any later detector task as accessible tracing only, with a clear stop line and no dismantling.
  3. Use the product page and manufacturer documentation to answer missing questions before relying on the instrument.

When a home purchase still makes sense

The HT601B+ may suit a buyer who understands that its documented features are a flexible probe, colour display, visual and audible alarms, stated ppm and LEL ranges, and USB charging of an internal lithium battery. It is not documented as a CO alarm, a formal tightness tester, an emergency monitor or a certification instrument.

If your need is emergency reassurance, a product comparison is the wrong task. Use the emergency number and qualified gas safety route first; make a detector purchase only for a separate, clearly bounded later use.

When gas is smelled, the right first purchase decision is no decision: follow the emergency service. Consider a handheld detector only for a later, documented tracing task. Read Soap Bubble Test vs Gas Sniffer UK: Safe Boundaries for related guidance. Read Caravan Gas Leak Detector UK: Safe Checks Before Travel for related guidance. Review the documented specification on the HABOTEST HT601B+ Handheld Gas Leak Detector product page before ordering.

Sources and safety context