There is no stop-work temperature in Australian workplace law, and that makes the heat duty bigger, not smaller

No heat code, no magic number

Start with what does not exist, because the gaps are where bad advice grows. Safe Work Australia publishes model codes of practice for noise, falls, chemicals and around thirty subjects in all; heat is not one of them. Nor is there a legal cut-off temperature. The SWA frequently-asked-questions page answers "Is there a maximum temperature where workers are required to stop work?" with a flat "No", because "a single 'stop work' temperature can't account for all the factors that make working in heat hazardous", listing humidity, airflow, the physical intensity and duration of the work, and whether workers are fit and acclimatised. What exists instead is a duty with no off switch. Regulation 40 requires a PCBU to ensure, so far as is reasonably practicable, that "workers carrying out work in extremes of heat or cold are able to carry out work without risk to health and safety", on top of the section 19 general duty. A fixed threshold would let an employer work people at one degree under it; the reasonably-practicable standard asks instead what this workplace, this task and these workers require today, which on a 38-degree afternoon may lawfully mean rescheduling the job. The instruments below fill in what that judgement should weigh.

The work environment code carries the indoor half

The model work environment and facilities code gives regulation 40 its working detail, and it is careful to separate two different problems. Thermal comfort is the 20 to 26 degree band it describes as optimum for sedentary work; heat that threatens health is a different matter, and the code says plainly that "it is important to distinguish between a condition that threatens health and safety, and a feeling of discomfort". Its heat-illness examples are indoor ones: foundries, commercial kitchens and laundries, where thermal radiation and humidity do the damage without the sun's help. Two of its requirements deserve more attention than they get. Where work involves prolonged or repeated exposure to heat, the environmental conditions and the health and safety of workers must be monitored, which means somebody measuring, not assuming. And where exposure cannot be eliminated, its control list runs the familiar hierarchy: fans and air-conditioning, insulating plant and pipes, local exhaust ventilation for hot processes, mechanical aids for manual tasks and rescheduling to cooler times, with slower pace, cool drinking water, rest areas and acclimatisation listed as the supporting measures that are "least effective if used on their own". Even the drinking water gets a number: at or below 24 degrees.

The heat guide is where the risk factors live

Safe Work Australia's Guide for managing the risks of working in heat, October 2021, is guidance rather than a code, and it is the most specific document in the set. Its risk-assessment chapter names the people standard heat policies overlook: workers aged 25 or under or 55 and over, workers on certain medications such as diuretics, pregnant workers, workers with diabetes, obesity, heart disease or a fever, anyone who has had a heat illness before, and workers returning after an absence, its example being a fly-in-fly-out worker whose acclimatisation has lapsed. It also names a work design trap: workers on performance-based pay are less likely to slow down to protect themselves, so piece rates are themselves a heat risk factor. Its control chapter starts where the hierarchy demands, elimination: cancel or reschedule the task until conditions pass, use a drone for the fire-ground inspection, prefabricate in an air-conditioned factory rather than assemble in the sun. On hydration it corrects folklore in one line: thirst is satisfied before fluid loss is replaced, so drinking to thirst is not enough. And its first-aid appendix is unambiguous about the far end of the scale: suspected heat stroke is a 000 ambulance call, with whole-body cold-water immersion for 15 minutes the most effective cooling while it comes.

Heatwaves, and who can lawfully stop the work

The guide defines a heatwave as unusually hot maximum and minimum temperatures over at least three days, and the minimums are the point: warmer nights cut sleep, and the resulting fatigue arrives at work with the heat. SWA points duty holders to the Bureau of Meteorology's Heatwave Service for the forecasts that should trigger the extra risk assessment, and its heatwave controls are scheduling ones: cooler parts of the day, less physical effort, self-paced work, no lone work where possible. When conditions outrun the controls, the law already says who can act. A worker can cease unsafe work, and a trained health and safety representative can direct workers in their work group to cease it, where there is a reasonable concern of serious risk from an immediate or imminent hazard; SWA's heat FAQ walks through exactly this. An employer who treats a hot-weather walk-off as a purely industrial matter has misread which Act is in play. The emergency-planning side, what regulation 43 expects when the plan meets a heat casualty in a confined space, is the guide's closing reminder: the rescue procedure has to work without delay.

The data barely sees heat, which is not the same as heat being rare

In the national claims table for 2023-24, "heat, electricity and other environmental factors" is a single combined mechanism: 1,900 serious claims, 1.3 per cent of the total, with median time lost of 2.4 weeks and median compensation of $3,800. Heat cannot be separated out of that line from the published report, and the fatality series is no help either: the 188 worker deaths counted for 2024 are traumatic-injury deaths, with fatalities from disease and natural causes excluded, which is where a heart attack in a heatwave would usually land. So the honest statement is that the national WHS statistics are not built to measure heat harm, and a duty holder should treat a quiet claims history as silence, not evidence of safety. The instruments above, the monitoring duty, the risk factors, the heatwave triggers, are the measurable record heat actually leaves.