A portable gas detector tells a worker what the air is doing before and during entry. Choosing one means matching the gases it measures to the hazards, then checking how it will be tested, calibrated and, on a mine site, accepted by your regulator. This guide uses Safe Work Australia's confined spaces code, the NSW Resources Regulator and the makers' own product information to explain the choices, with the MSA ALTAIR range we supply as the examples. It is general information and does not replace your site's gas management plan or the advice of your gas or ventilation officer.
What should a portable gas detector measure?
Safe Work Australia's Model Code of Practice for confined spaces says air monitoring should check oxygen content, flammable contaminants and potentially harmful contaminants such as hydrogen sulphide and carbon monoxide. It should be carried out by a competent person using a suitable, correctly calibrated gas detector. A person's senses should never be used to decide whether the air is safe, because many toxic or flammable gases and unsafe oxygen levels cannot be detected that way.
That is why a four-gas monitor is the usual starting point: oxygen (O2), combustible gas as a percentage of the lower explosive limit (LEL), carbon monoxide (CO) and hydrogen sulphide (H2S). Other sensors, such as nitrogen dioxide (NO2) or sulphur dioxide (SO2), are added when the work calls for them. The mines-registered ALTAIR 4XR below reads methane (CH4) in place of LEL.
How do the MSA ALTAIR detectors compare?
| Model | Gases | What the listing says | Suits |
|---|---|---|---|
| ALTAIR PRO 10074137 | O2 | Alarm set points of 19.5% (low) and 23.0% (high), adjustable. Logs the last 50 alarm and test events. | Oxygen checks only |
| ALTAIR 2X 10153986 | CO | IP67 and an intrinsically safe design. Sensor life over 4 years. | Single-hazard carbon monoxide checks |
| ALTAIR 2XT 10153985 | SO2 and H2S | IP67 and an intrinsically safe design. Sensor life over 4 years. | Two-gas sulphur checks |
| ALTAIR 4XR 10178585 | LEL, O2, CO, H2S | IP68 (2 m for at least 1 hour). Third-party certified to survive 25 drops from 1.2 m. Operates from -40°C to +60°C. | The standard four-gas confined space set |
| ALTAIR 4XR, mines registered 10204302 | CH4, O2, CO, H2S | Same rugged housing as the 4XR. Methane instead of LEL. Listed as mines registered. | Underground coal, where your site's approvals allow it |
| ALTAIR 5X 10119666 | LEL, O2, CO, H2S, NO2 (up to 6 gases) | Integral pump. IP65. Survives a 3 m drop. Optional PID sensor for VOCs. Bluetooth. | Work that needs NO2 or a sixth gas, or pumped sampling |
Figures are from the manufacturer information on each product listing. The ALTAIR 4XR kit in a carry case adds a regulator, calibration assembly, test gas and a foam-lined case.
What does 'mines registered' mean?
MSA's mining brochure for the ALTAIR 4X says methane explosions in underground coal mines remain a serious risk, and that the mining version uses a methane-optimised sensor for better stability over time. Our listing for the ALTAIR 4XR 10204302 calls it mines registered.
Mine safety law is set state by state. In NSW, for example, the design of an electrically powered hand-held gas detector must be registered if it is used at an underground coal mine, and the Resources Regulator publishes a gas detector design order that sets the minimum performance a design must meet. Another state, or your own site, may ask for something different. The listing does not give registration numbers, so ask us or MSA for the paperwork your mine needs, and confirm the model with your site's gas or ventilation officer or your regulator before you order.
What is the difference between a bump test and a calibration?
A bump test exposes the detector to test gas for a short time to confirm that the sensors respond and the alarms work. A calibration adjusts each sensor to a known gas concentration. Your detector's manual and your site's procedure decide how often each is done, and the confined spaces code expects the detector to be correctly calibrated.
On the ALTAIR 4XR, a bump LED and an on-screen checkmark show bump status at a glance. The GALAXY GX2 test stand (also available for the ALTAIR 5X) can bump test, calibrate and charge a bank of detectors automatically. The test gas has to match the sensors. Our 34 L and 58 L ALTAIR four-gas cylinders hold 1.45% CH4, 15% O2, 60 ppm CO and 20 ppm H2S, with the lot number and nominal value of each gas marked on the cylinder.
How do you test the air in a confined space?
Safe Work Australia's code sets out the order of work:
- Start from outside. Initial testing is done by putting a sample probe or portable gas detector through access holes, nozzles or other openings before anyone enters.
- Test every level. Contaminants settle at different heights, so test side to side and top to bottom. Hydrogen sulphide is heavier than air and settles at the bottom of an unventilated space, while methane is lighter and collects at the top.
- Know the flammable limits. The code says flammable gas should be below 5% of its LEL while work is carried out, so far as is reasonably practicable. Between 5% and 10% the worker must be removed unless a gas detector is used, and at 10% or more the worker must be removed immediately.
- Keep monitoring. Entry also needs communication with the worker and a stand-by person who watches conditions in the space.
Mines and petroleum sites work under their own state legislation, which can differ from the model code, so treat this as a baseline and follow your site's procedures.
Which gas detector suits which job?
- Tanks, pits, sewers and general confined space entry: a four-gas detector (LEL, O2, CO, H2S) such as the ALTAIR 4XR.
- Underground coal: the mines-registered ALTAIR 4XR, if your site's approval requirements are met.
- Work that adds nitrogen dioxide, or needs a sixth sensor or pumped sampling: the ALTAIR 5X. Its listing describes an integral pump; our 4XR listings do not mention one, so ask us before ordering if you need to draw samples through a probe.
- One-hazard checks: the ALTAIR PRO (O2), 2X (CO) or 2XT (SO2 and H2S).
- A fleet of detectors: a GALAXY GX2 test stand and a matching supply of calibration gas.
Not sure which suits your site? Contact our team with the gases and the work, and we will point you to the right model. Mine approvals remain your site's call.
Shop Gas Detectors and Confined Space Gear
Sources: Safe Work Australia: Model Code of Practice, Confined spaces (2024); NSW Resources Regulator: Plant registration and its Gas detector design order fact sheet (March 2023); MSA Safety: Multigas detectors in mines (brochure); and the manufacturer information on each 1st Safety product listing. This guide summarises these sources in our own words. It is general information, not legal advice.
1st Safety is based in Auburn, NSW, and supplies AS/NZS-compliant PPE to trades, construction, and industrial businesses across Australia.
Frequently Asked Questions
What is the difference between a 4-gas and a 5-gas detector?
A four-gas detector such as the ALTAIR 4XR measures LEL, oxygen, carbon monoxide and hydrogen sulphide. The ALTAIR 5X can monitor up to six gases at once; the configuration we list adds nitrogen dioxide, and MSA offers an optional PID sensor for VOCs. The 5X listing also describes an integral pump.
Do I need a different gas detector for underground coal mines?
Usually, yes. Underground coal monitoring is built around methane, and mine safety law sets its own approval requirements by state. MSA sells a mines-registered ALTAIR 4XR for methane, oxygen, carbon monoxide and hydrogen sulphide. Whether it meets your mine's requirements is for your gas or ventilation officer or your regulator to confirm.
How often should a gas detector be bump tested and calibrated?
Follow the maker's manual and your site's procedure. Safe Work Australia's confined spaces code says air monitoring should use a suitable, correctly calibrated gas detector. Automated test stands such as the MSA GALAXY GX2 can run bump tests and calibrations at a set time of day.
Can I rely on smell or symptoms instead of a detector?
No. Safe Work Australia says a person's senses should never be used to decide whether the air in a confined space is safe, because many toxic or flammable gases and unsafe oxygen levels cannot be detected that way.
Are the ALTAIR detectors intrinsically safe?
The ALTAIR 2X and 2XT listings state an intrinsically safe design, and the ALTAIR 4XR kit listing states certification to AS/NZS (IEC) 60079-0 and 60079.11. Zone and gas-group ratings differ by model, so check the certificate for the one your site needs.
What test gas do ALTAIR four-gas detectors use?
Our 34 L and 58 L ALTAIR four-gas cylinders hold 1.45% methane, 15% oxygen, 60 ppm carbon monoxide and 20 ppm hydrogen sulphide, with the lot number and nominal value of each gas marked on the cylinder.
Can I buy a complete gas detector kit?
Yes. The ALTAIR 4XR kit in a carry case includes the detector, a regulator, a calibration assembly, test gas and a foam-lined carry case.
Can you supply a whole site or crew?
Trade pricing and account terms are available, so contact our team or call 0457 545 175. We're based in Sydney, with fast dispatch Australia-wide.