Confined Space &
Compliance

Confined space work kills people who did everything except the one thing that mattered. The permit was raised, the space was ventilated, the standby was in position, and the atmosphere was tested with an instrument that had quietly stopped working.

What follows is drawn from work our engineers have done on Australian sites, including some detail about how gas detection fails that does not appear on a datasheet.

A Confined Space Is A Legal Test, Not A Size

Under Regulation 5 of the Work Health and Safety Regulations, a confined space is an enclosed or partially enclosed space that is not designed or intended primarily for human occupancy, and in which there is a risk of an oxygen concentration outside the safe range, an airborne contaminant that could cause impairment or loss of consciousness, or engulfment.

Volume does not decide it. A large tank can be a confined space and a small cupboard need not be. What decides it is the combination of restricted access, an atmosphere that can go wrong, and a space nobody was meant to be standing in.

AS 2865-2009 sets out the technical requirements for safe entry and remains the primary Australian standard. Part 4.3 of the WHS Regulations carries the legal duties, and the Safe Work Australia model Code of Practice for confined spaces, updated in November 2024, is the guidance that inspectors work from.

The Safest Entry Is The One You Do Not Make

The hierarchy of control puts elimination first, and in confined space work that duty falls partly on designers. A designer, manufacturer, importer or supplier must eliminate the need to enter a confined space so far as is reasonably practicable, and eliminate the risk of inadvertent entry.

That is not always a paper exercise. Gastech supplies gas detection for sewer tunnel flotation platforms, which exist for exactly this reason. Once a deep sewer tunnel has been cleaned and ventilated, a float is lowered through a vertical access point and travels along the horizontal tunnel on guide ropes, connected by a lightweight umbilical, covering at least 300 metres. It carries thermal imaging, acoustic sensors, temperature, audio and visual sensors, spotlights and, near the top of the priority list, fixed gas detection.

Operators sitting in a non-hazardous area watch and record what the float finds, and then decide what maintenance is needed and whether anyone has to go in at all. The gas set is hydrogen sulphide, oxygen, ammonia and methane, and the practical constraints are unusual: sensors have to be positioned correctly on a moving float, tolerate extreme humidity and momentary submersion, and communicate over RS-485 to keep cable weight down.

Where entry cannot be eliminated, everything below applies.

Testing Before Entry, In The Right Order

Pre-entry testing covers oxygen, flammable gas and toxic contaminants, and the flammable threshold is the one most often quoted. Flammable gas must be below 10 percent of the lower explosive limit before anyone enters.

Order matters. Test from the top of the space down, because gases stratify. Methane collects high, carbon dioxide and hydrogen sulphide collect low, and a reading taken at the manhole tells you about the manhole. A sampling probe and tubing with a pumped instrument lets the space be tested at depth before a body goes into it, which is the whole point.

The Part Nobody Tells You About Catalytic Bead Sensors

This is the most important thing on this page.

The most common sensor for measuring LEL is the catalytic bead, also called a pellistor or Wheatstone bridge sensor. It works by burning gas on a heated element and measuring the temperature change, and it has been the standard for decades.

It has two failure modes that matter in a confined space.

The first is that catalytic bead sensors fail to an unsafe state. When they fail, they indicate safe levels of flammable gas. They do not read high, they do not fault, they read clean. Silicones, sulphur compounds and lead poison them, and common chemicals found in industrial environments can render the sensor inoperable without any outward sign. The only way to establish whether a catalytic bead sensor still works is to challenge it with calibration gas, ideally methane. Which is why a bump test before use is not a paperwork exercise, it is the only thing standing between a poisoned sensor and a fatality.

The second is accuracy on heavier fuels. Heavier hydrocarbon vapours diffuse poorly into the sensor and give a weak response. Jet fuel is more than three times less sensitive than methane, so measuring jet fuel on a catalytic bead sensor carries an error of around 5 percent LEL. At the 10 percent LEL entry threshold, that is an error of 50 percent of the reading.

Where A PID Does The Job Better

A photoionisation detector offers an alternative for measuring 10 percent of LEL.

PIDs use an optical technology, so they cannot be poisoned in the way a catalytic bead can. Accuracy is around 10 percent of the reading. Reviewing more than 175 common flammable chemicals, catalytic bead sensors typically carry three times the range of uncertainty of a PID when measuring 10 percent of LEL, and for jet fuel specifically the difference is closer to five times.

There is an important caveat and it is worth stating plainly. If a PID is used as the sole means of measuring flammable gases, you must be certain it can see all the flammable gases expected in that space. A PID will not detect methane, which is exactly the gas most likely to be present in a sewer or a digester.

Monitoring During Entry, Not Only Before It

A pre-entry test describes the atmosphere at one moment. Conditions change once people, tools and disturbance are introduced. Sediment gets stirred, sludge releases trapped gas, hot work consumes oxygen, and ventilation stops working if a fan trips.

Continuous monitoring during occupancy is the requirement, which in practice means a personal instrument on each entrant plus something the standby can see. Wireless enabled portables solve a real problem here, because a standby watching a hole cannot see the readings on an instrument three metres below them. The Ventis Pro 5 and the Radius BZ1 share readings and alarms across a work group, so an alarm inside the space is an alarm at the entry point.

An area monitor at the access point covers the space around the entry as well, which matters where the hazard can migrate out of the opening.

Ventilation, And How To Tell It Is Working

Ventilation is the primary engineering control for a confined space, and the way to confirm it is working is to measure rather than assume.

Air change rate has historically been set against generic tables by venue type. Practice has shifted toward using carbon dioxide concentration in parts per million as the measure, because it is the most reliable indicator of how well air is actually being replaced. Required air change rate depends on the target CO2 concentration, the outdoor CO2 level, the volume of the space, the number of occupants and what they are doing.

A four step check confirms it: measure incoming air flow, measure outgoing air flow, check overpressure inside the space, and check the CO2 level. If CO2 is climbing while the fan is running, the fan is not doing what the permit assumes.

Compressed Breathing Air Needs Testing Too

Where breathing apparatus is connected to compressed air lines rather than cylinders, the air itself is a hazard nobody tests.

A failing compressor puts oil into the air line, which the wearer then inhales as oil mist. Water vapour, excess carbon dioxide and carbon monoxide all accumulate for their own reasons. The effects run from headaches, dizziness and nausea through to vomiting, and the wearer has no way of knowing.

Testing uses colorimetric tubes or measuring devices connected directly to the compressor line or cylinder, and critically placed downstream of the filters, so the air tested is the air that will be breathed. A Gastec CG-1 tube kit typically measures carbon dioxide from 250 to 3,000 ppm, carbon monoxide from 5 to 50 ppm, oil mist from 0.2 to 5.0 mg/m³ and water vapour from 20 to 80 mg/m³. For continuous monitoring, the Analox ACG+ checks the air all the time and can shut the compressor down on alarm. AS/NZS 1715 sets out the requirements for breathing air used with respiratory protective equipment.

Where Confined Spaces Turn Up

Sewers, manholes and storm water systems, where the risk is not only sewer gas. Fuel spillages, chemical or solvent dumping, fertilisers, pesticides, factory waste and natural gas ingress all find their way into water systems, which is why the flammable risk in a storm water tunnel is frequently underestimated.

Tanks, vessels and process reactors. Silos and grain storage, particularly where fumigation has been used. Composting tunnels, in-vessel systems, pits and the areas beneath piles, where oxygen depletion and hydrogen sulphide are the acute risks. Anaerobic digesters and biogas plant. Pump stations and wet wells. Ship holds and ballast tanks. Boilers, ducts and flues. Trenches and excavations. Refuge chambers, which are a confined space designed to be occupied.

The Compliance Half

Confined space entry generates paperwork, and most of it depends on gas detection records.

A risk assessment must be conducted by a competent person and recorded in writing. Entry permits reference the atmospheric test results. Instruments need bump testing before use and calibration on schedule, and both need evidence. If an incident is investigated, the calibration history of the instrument that cleared the space will be looked at closely.

That record keeping is what G-Manager exists for, giving visibility of which instruments are in calibration, which are due and which have been bump tested. Docking stations automate the bump test and hold the record without anybody filling in a sheet. NATA calibration and service provides the certificates, and field service does it on site where sending instruments away is not practical.

For campaign work such as a shutdown, hire covers the peak without buying instruments that sit idle for the rest of the year, and hire units arrive calibrated with certification.

Who Regulates It

Confined space entry falls under general work health and safety law rather than mining or petroleum legislation, so the regulator is the general WHS regulator in each state.

Safe Work Australia develops the model WHS laws and publishes the model Code of Practice for confined spaces, but it is not a regulator and does not enforce anything.

In Western Australia the regulator is WorkSafe WA, under the Work Health and Safety Act 2020 and the Work Health and Safety (General) Regulations 2022.

In New South Wales it is SafeWork NSW, under the Work Health and Safety Act 2011 and its Regulation, except for mines and petroleum sites which sit with the Resources Regulator.

In Queensland it is Workplace Health and Safety Queensland, under the Work Health and Safety Act 2011 and its Regulation.

The duties are substantially the same across all three because the laws are harmonised, but the codes of practice and the inspectorate differ, so a national operator should not assume one state’s documentation satisfies another.

What Gastech Supplies

Portable multi-gas detectors for pre-entry testing and personal monitoring, in pumped and diffusion form, with four gas instruments covering the standard set and five plus gas instruments where the space needs more.

PID instruments for accurate measurement at the 10 percent LEL threshold and for volatile organic compounds a catalytic bead sensor will read poorly.

Wireless enabled portables and area monitors so the standby sees what the entrant sees.

Docking stations for automated bump testing, calibration and record keeping, and sampling probes, tubing and accessories for reaching into a space before entering it.

Fixed gas detection for permanent installations at access points, pump stations, spill pits and remote inspection platforms.

Behind it sit project engineering, NATA calibration and service, field service, fleet management and hire, from WA, NSW and QLD.

If you are reviewing a confined space procedure, or working out whether your instruments can actually see what is in the space, talk to our Technical Consultants.