An invisible, odourless gas that has killed at work
Carbon monoxide (CO) is a common and deadly poison that has caused serious illness and deaths in New Zealand workplaces. It is invisible, with no smell or taste, so people can breathe dangerous levels and not realise. It builds up fast where fuel-burning engines run in enclosed or poorly ventilated spaces — petrol plant, generators, LPG or petrol forklifts indoors. Control it by removing the source or ventilating, and, where a hazardous atmosphere is possible, test the air with a correctly calibrated gas detector before anyone enters.
Carbon monoxide is produced whenever fuel burns. It is invisible and has no smell or taste, and it doesn't irritate your nose, mouth or skin — so workers can be poisoned without warning. Early symptoms are headache, dizziness, nausea, stomach pain, tiredness and confusion; at higher levels it causes shortness of breath, brain and heart damage, and death. CO is measured in parts per million (ppm) and has a workplace exposure standard.
The danger is fuel-burning engines running in enclosed or poorly ventilated spaces: petrol or diesel plant in containers, sheds or tanks; generators; and petrol or LPG forklifts used indoors. A New Zealand contractor died after a petrol engine's exhaust built up in a shipping container. Never run liquid-fuel engines in confined or poorly ventilated areas.
| Control | What it looks like |
|---|---|
| Substitute | Use electric or pneumatic tools instead of fuel-powered ones where reasonably practicable, and move CO-producing processes outside. |
| Ventilate | Install ventilation to capture contaminated air and extract it safely outside; keep fuel-powered forklifts well tuned to keep emissions low. |
| Monitor | Monitor the work environment, and monitor worker health where exposure warrants it; prefer controls that protect everyone at once. |
| Inform & protect | Train workers on the dangers and emergency response, and use respiratory protection only as a last line, not the main control. |
Where a hazardous atmosphere is possible — especially before entering a confined space — test the air first, without entering where you can. Test for toxic gases (CO, hydrogen sulphide, methane), flammable vapours, and oxygen level (an oxygen-enriched atmosphere above about 23.5% increases the explosion risk). Use appropriate detectors, kept correctly calibrated: bump-test before each use and calibrate at regular intervals. Ventilate, then re-test to confirm levels are below the exposure standard before entry, and stay alert for any change in conditions. Manage stored gas separately under gas cylinders & compressed gas.
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Because it is invisible and has no smell or taste, so workers can breathe dangerous levels without realising. It causes headache, dizziness and confusion, and at higher levels brain and heart damage or death. It has caused deaths in New Zealand workplaces.
Where fuel-burning engines run in enclosed or poorly ventilated spaces — petrol or diesel plant in containers or sheds, generators, and petrol or LPG forklifts used indoors. Never run liquid-fuel engines in confined or poorly ventilated areas.
Remove the source first — use electric or pneumatic tools, or move the work outside — then ventilate to extract the gas, keep fuel-powered forklifts well tuned, and monitor the environment. Respiratory protection is a last line, not the main control.
Whenever a hazardous atmosphere is possible, especially before entering a confined space. Test for toxic gases, flammable vapours and oxygen level before entry, without entering where you can.
Bump-test it before each use and calibrate it at regular intervals. A detector that is not bump-tested and calibrated can't be relied on to keep workers safe.
