Analysis & Monitoring
Portable and fixed gas detectors, toxic and combustible gas sensors, leak detectors and flame detection systems.
Gas detection exists to protect people, so it is specified around the hazard rather than around a measurement. Which gases have to be detected, what concentration matters, how quickly the alarm has to arrive, and whether the instrument is worn by a person or fixed in an area - those questions decide the configuration, and performance figures come afterwards.
The two families behave quite differently. A portable detector is carried into a confined space or worn through a shift, so weight, battery life, robustness and a daily bump test dominate. A fixed system runs continuously with a controller, alarm relays and often voting logic between detectors, so coverage, placement and the consequence of a false alarm dominate instead.
Both depend on sensors that are calibrated against a certified test gas at defined intervals, and on sensor elements that are consumed or degraded over time. That makes the calibration regime and the sensor replacement route a real part of the specification rather than an operating detail - a detector whose sensor cannot be replaced locally has a maintenance lead time built into it.
| Product type | How it senses | Usually specified for |
|---|---|---|
| Portable single-gas detector | One sensor element in a worn instrument with a local alarm | Personal protection through a shift, where one known hazard dominates and the instrument has to be light and simple to use |
| Portable multi-gas detector | Several sensor elements in one instrument, commonly including oxygen and a combustible channel | Confined-space entry, where the atmosphere has to be checked for several hazards before and during entry |
| Fixed gas detector | A sensing head installed at a point and wired back to a controller or a control system | Area protection where the hazard is expected to accumulate at a known place, such as a valve, a pit or a compressor house |
| Combustible gas detector | Catalytic or infrared measurement of a flammable gas in air | Areas handling flammable gas or vapour, where the alarm is set as a fraction of the lower explosive limit |
| Toxic gas detector | An electrochemical cell selected for a specific substance | Areas where a known toxic gas could be released, and any exposure limit that has to be monitored continuously |
| Oxygen detector | An electrochemical cell measures oxygen directly, for both deficiency and enrichment | Confined spaces, inert-gas purging, and any room where displacement or consumption of oxygen is possible |
| Gas leak detector | A sensitive sensor used to locate a leak rather than to monitor an area | Commissioning, maintenance and leak surveys on pipework, joints and manifolds |
| Flame detector | Ultraviolet or infrared sensing of the radiation a flame emits | Areas where a fire could develop before gas accumulates, and where an ignition event rather than a concentration is the risk |
Gas detection systems, controllers and general industrial safety instruments are listed under this category as well.
There is rarely a single correct instrument for a duty, but there is always a shortlist that can be justified and a set of answers that eliminates the rest. These are the questions that decide it.
| Sensor technology | Best suited to | Limits | Detects |
|---|---|---|---|
| Catalytic bead | Combustible gas where a broad response across many hydrocarbons is acceptable | Poisoned by silicones, sulphur compounds and lead, and needs oxygen present to measure at all | Combustible gas |
| Infrared | Combustible gas in locations where sensor poisoning would end the catalytic sensor life | Only responds to gases with a suitable absorption band, so some substances are outside its reach | Combustible gas, carbon dioxide |
| Electrochemical cell | Toxic gases and oxygen, at the concentrations exposure limits are written in | Consumed over time and needs replacing; cross-sensitivity between gases is common and has to be allowed for | Specific toxic gases, oxygen |
| Photoionisation | Volatile organic compounds at low concentration, and leaks of solvent vapour | The lamp energy decides which compounds respond, and the lamp and window are consumables | Volatile organic compounds |
| Metal-oxide semiconductor | General leak indication and trend detection at a modest cost | Affected by humidity and temperature, and not selective, so it indicates that something is present rather than what | Leak indication |
| Ultraviolet and infrared flame sensing | Flame itself, in areas where ignition could precede any significant gas cloud | False alarms from welding, hot work and sunlight unless the detection logic and the siting are set correctly | Flame |
What is left after the technology is chosen is a list of values that only the installation can supply. These are the ones that change the model, the price or the lead time:
Specifications vary by model and application, so no performance figure is stated on this page. Where a parameter has not been documented for a particular model, the product page says so rather than filling the gap with a plausible number. Send the values above and we will return the ones the selected model actually holds.
Frequently asked
The questions that come up before an order rather than after it. If yours is not here, send it with the requirement and we will answer it in the quotation.
By whether the hazard moves with the person or sits at a point. A confined space entered occasionally, a maintenance task on a line, or a walk-round inspection is served by a portable instrument worn or carried by the person. A compressor house, a valve station or a pit where gas would accumulate is served by fixed detection wired to a controller. Many sites need both, applied to different parts of the same plant.
Because catalytic elements are poisoned by substances that are common in industry - silicones, sulphur compounds and lead - and once poisoned they respond less or not at all. In locations where those substances are present, an infrared sensor is often chosen instead, since it does not depend on a catalyst being active. It is worth describing the full atmosphere rather than only the target gas.
Catalytic combustible sensors do, because the measurement relies on combustion at the element, so an inert or oxygen-depleted atmosphere affects them. Infrared sensors do not have that limitation. Where a space might be purged or inerted, this distinction decides which technology is usable, and it should be stated in the enquiry along with the gases involved.
It is a brief exposure of the sensor to a known test gas to confirm that it responds and that the alarms operate, in contrast with a full calibration that adjusts the reading. The interval is normally set by the site procedure or the applicable standard rather than by the instrument, and practical sites carry them out before each shift for personal detectors. The test gas and the procedure have to be available locally for it to be sustainable.
From the geometry and from how the gas behaves, not from the floor area. A gas heavier than air collects in pits and low corners, one lighter than air collects at the ceiling, and a draught from a doorway or a louvre moves the accumulation point. Coverage follows from the gas, the ventilation and the shape of the space, so the layout matters as much as the count.
No - they answer different questions. Gas detection responds to a concentration before ignition, while flame detection responds to a fire that has already started. Where a release could ignite immediately, or where gas would disperse too quickly to be detected reliably, flame detection is the applicable protection rather than a substitute for gas detection. Sites with both risks usually install both.
Available now
BH-4 / BH-90 · Portable Gas Detectors
Hand-held multi-gas and single-gas detectors with audible, visual and vibrating alarms, covering the four-gas confined space combination as standard and a long list of single gases to order.
GQ-KL800-L4 · Fixed Gas Detectors
A point gas detector in an explosion-proof cast aluminium housing for continuous monitoring of combustible gas, oxygen, hydrogen sulphide and carbon monoxide, supplied as a stand-alone unit or with a controller over wired or wireless links.
JLY-CP100 / BT-JLY-CP100 · Gas Leak Detectors
Portable combustible gas leak detector reading 3 to 20 percent of the lower explosive limit with a flexible gooseneck probe, a three-way alarm and a full-colour display.
Send the specification and we will confirm the matching instrument, availability and lead time. Minimum order quantity is 1 pc.
Request for quotation
Send the technical detail and we will confirm availability, lead time and terms. In-stock items ship within 48 hours; customized specifications typically take 2-10 days. Minimum order quantity is 1 pc.