Browse Gas Detectors
Personal and portable gas detectors
Portable detectors go where your people go. They’re used for personal safety, leak checks, surveys and emissions testing across industrial, emergency response and service work.
Personal gas monitors
Detects: Toxic gases · Combustible gases · Oxygen
Personal gas monitors are worn on the body or carried by hand, and alert the wearer with alarms when gas reaches a dangerous level, so they can act quickly. Single-gas monitors track one specific hazard, such as hydrogen sulfide or carbon monoxide. Multi-gas monitors measure several gases at once. They’re used in industrial plants, emergency and hazmat response, plant shutdowns, oil and gas, environmental work and public safety.
VOC monitors and detectors
Detects: Volatile organic compounds (VOCs)
Volatile organic compounds (VOCs) are carbon-based chemicals, such as solvents and fuels, that evaporate readily at room temperature. VOC monitors use photoionisation detection (PID) to measure them quickly and at very low concentrations. They’re used for industrial hygiene, leak detection and hazmat response, including in harsh environments.
Combustion flue gas analysers
Detects: Oxygen · Carbon monoxide · other combustion gases
Hand-held flue gas analysers measure the gases in combustion exhaust, typically oxygen and carbon monoxide, and calculate values such as combustion efficiency. They’re used by heating, automotive and electrical service technicians for emissions testing, safety checks and burner tuning.
Fixed and area gas detection
Fixed detectors monitor an area continuously, around the clock, and can trigger alarms, ventilation or shutdowns automatically when gas is detected.
Fixed gas detection systems
Detects: Toxic gases · Combustible gases · Oxygen
We supply fixed gas detection systems, primarily from Honeywell. A fixed system places gas detectors at the points where a leak is most likely, wired to a controller or directly to your PLC or building management system. Detectors typically send a 4–20 mA or digital signal, and the controller drives relays for alarms, beacons, fans and valves. A well-designed system matches the detector type and location to the gas: heavier-than-air gases are detected low, and lighter gases high.
Refrigerant gas monitors
Detects: Refrigerants
Refrigerant monitors detect leaks from refrigeration and air-conditioning systems. They help you meet health and safety requirements in plant rooms and occupied spaces, find small leaks before they become large ones, and reduce refrigerant loss. Monitors are available for occupied spaces served by variable refrigerant flow (VRF) systems, where a leak could otherwise build up unnoticed.
Ground gas data loggers
Detects: Ground gases, such as methane and carbon dioxide
Ground gas can build up around landfills, contaminated land and new developments. A portable in-borehole data logger sits in a monitoring borehole and records gas levels unattended over long periods, giving you real trend data rather than one-off spot readings.
Gas detection sensor technologies
The sensor inside a detector decides which gases it can see, how selective it is, and how it should be maintained. These are the main technologies you’ll come across.
Electrochemical sensors
Detects: Toxic gases · Oxygen
Electrochemical sensors are the most common choice for toxic gases, such as carbon monoxide, hydrogen sulfide, chlorine and ammonia, and for oxygen. The target gas diffuses into the sensor and reacts at an electrode, producing a small current proportional to its concentration. They’re sensitive and selective, but the sensor has a limited life and needs periodic replacement. For more detail, see Analytical Instrumentation.
Catalytic bead (pellistor) sensors
Detects: Combustible gases
Catalytic bead sensors detect combustible gases such as methane, propane and hydrogen. The gas burns on a heated catalyst bead, which raises its temperature and changes its electrical resistance. They need oxygen to work, and some substances, such as silicones, can poison the catalyst, so regular calibration matters.
Infrared (NDIR) sensors
Detects: Combustible gases (hydrocarbons) · Carbon dioxide · Refrigerants
Infrared sensors measure how much infrared light a gas absorbs at a wavelength specific to that gas. They’re widely used for hydrocarbons, carbon dioxide and many refrigerants. Because the gas doesn’t react with the sensor, they can’t be poisoned, work without oxygen and have a long life.
Photoionisation detectors (PID)
Detects: VOCs
A PID uses ultraviolet light to ionise gas molecules and measures the resulting current. It responds to a very wide range of VOCs at low concentrations, but isn’t selective: it gives a total reading, which correction factors convert for a specific compound.
Semiconductor sensors
Detects: Refrigerants · some combustible and toxic gases
Semiconductor (metal oxide) sensors change resistance when gas adsorbs onto their heated surface. They’re economical and sensitive, and are often used in refrigerant and general leak monitors, but they’re less selective than other types and can respond to other gases and humidity.
Calibration gas and service
A gas detector is only as reliable as its last calibration. We supply what you need to check your detectors, and we calibrate, repair and certify them for you.
Calibration gas and regulators
We supply specialty and high-purity calibration gases, gas cylinders, cylinder valves and regulators for gas detection, environmental, petrochemical and industrial applications.
IANZ-accredited calibration and repair
Teltherm is accredited by IANZ to ISO/IEC 17025, which means we’ve shown that we operate competently and produce valid results. We operate the only IANZ-endorsed gas detection laboratory in New Zealand. Our technicians can fault-find, repair, replace, test and certify your gas detection instruments, and our reminder system tells you when each one is next due for calibration. See Instrument Calibration NZ for more.
Choosing the right gas detector
The right detector depends on the gases you need to find, where the risk is, and who needs to be alerted. Start with these questions:
• which gases are present, and at what concentrations they become hazardous
• whether you need to protect individual workers (personal), an area (fixed) or check equipment (portable)
• what should happen on alarm: a local alert, a signal to your control system, ventilation or shutdown
• the environment: temperature, humidity, dust and any substances that could poison a sensor
• hazardous area, compliance and certification requirements.
Which sensor suits which gas?
| Sensor technology | Toxic gases | Combustible gases | VOCs | Refrigerants |
|---|---|---|---|---|
| Electrochemical | ✓ (and oxygen) | – | – | – |
| Catalytic bead | – | ✓ | – | – |
| Infrared (NDIR) | Carbon dioxide | ✓ (hydrocarbons) | – | ✓ |
| Photoionisation (PID) | – | – | ✓ | – |
| Semiconductor | Some | Some | – | ✓ |
How often to calibrate
We recommend calibrating gas detectors every six months, with a bump test before each use. A bump test exposes the detector to a small amount of test gas to confirm it responds and alarms.
Frequently asked questions (optional)
How often should gas detectors be calibrated?
We recommend every six months, with a bump test before each use. Your equipment documentation, site procedures or regulator may set a different interval, and a detector should always be checked after exposure to high gas levels or a suspected poisoning event.
What’s the difference between a bump test and calibration?
A bump test is a quick functional check that the detector responds and alarms when exposed to gas. Calibration uses certified gas of known concentration to adjust the detector so its readings are accurate, and is documented on a certificate.
Which detector do I need for VOCs?
A photoionisation detector (PID). It responds quickly to a wide range of volatile organic compounds at low concentrations. Because it isn’t selective, correction factors are used to report a specific compound.
Do you supply calibration gas?
Yes. We supply specialty and high-purity calibration gases, cylinders, valves and regulators for gas detection and industrial applications.