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Carbon monoxide - Invisible and deadly (Fact Sheet)
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Carbon monoxide - Invisible and deadly (Fact Sheet)

This fact sheet is for persons conducting a business or undertaking (PCBUs) and explains how to deal with health and safety risks arising from carbon monoxide.

Carbon monoxide is a common and deadly poison.

It has no smell, no taste, doesn’t irritate your nose, mouth or skin and it is invisible. It has caused serious illness and deaths at work.

It is impossible to detect carbon monoxide without the use of monitoring equipment.

You must, so far as is reasonably practicable, ensure the health and safety of workers, and that others are not put at risk from your work. To safely manage the health and safety risks from carbon monoxide, it’s important to know what to look for and what to do.


Where can carbon monoxide be found?

Carbon monoxide comes from a range of sources, including emissions from:

  • incompletely burned carbon-based material (eg wood, paper, fuel)
  • internal combustion engines (cars, trucks, forklifts, small portable petrol engines, etc)
  • kilns
  • furnaces and fuel-powered boilers
  • welding
  • plastics moulding
  • space heaters, oil or gas heaters
  • fires and explosions.


How can carbon monoxide affect the body?

Carbon monoxide is easily absorbed through the lungs into the bloodstream where it attaches to the red blood cells and stops them transporting oxygen to the body. The brain and heart are particularly susceptible to damage caused by a reduction in oxygen supply.

Carbon monoxide can be absorbed through a pregnant woman’s bloodstream into the foetus, where, depending on the amount of exposure, it may put the unborn baby at risk of brain damage and heart defects.

The first symptoms of carbon monoxide poisoning are mild headaches and dizziness. Most people recover from this low-level exposure without permanent damage.

Concentration of carbon monoxide in air[1]

Symptoms that may occur at this concentration

35 ppm[1]

Headaches and dizziness within six toeight hours ofcontinual exposure.

100 ppm

Headache within two to three hours.

200 ppm

Headache within two to three hours;loss of judgement.

400 ppm

Headache withinone to two hours.

800 ppm

Headache, dizziness, nausea and convulsions within45 minutes; unconsciouswithintwo hours.

1,600 ppm

Headache,acceleratedheart rate, dizzinessand nausea within 20 minutes; death in less than two   hours

3,200 ppm

Headache, dizziness and nauseawithin fiveto ten minutes; death within 30 minutes.

6,400 ppm

Headache and dizziness in one to two minutes; convulsions, breathing stops, and death in less than20 minutes.

12,800 ppm

Unconsciousness after two to threebreaths; death in less than three minutes.

Table 1: Symptoms  after carbon  monoxide exposure


How can you keep workers safe?

You must eliminate risks that arise from your work so far as is reasonably practicable. If you can’t eliminate the risk, you must minimise it so far as is reasonably practicable.

‘Reasonably practicable’ means doing what is reasonable in your circumstances to ensure health and safety.

For further information, read WorkSafe’s fact sheet Reasonably Practicable.


To eliminate the risks you could:

  • use electric forklifts instead of fuel-powered forklifts
  • move carbon monoxide-generating processes  outside
  • use electrical, hydraulic or pneumatic tools instead of fuel-powered tools.


To minimise the risks you could:

  • install ventilation in work areas that captures the contaminated air and extracts it safely outside
  • regularly tune fuel-powered forklifts to ensure that carbon monoxide emissions are as low as possible.

Give preference to control measures that protect multiple people at once.

Seek your workers’ views on which control measures to use.


Monitoring the work environment

PCBUs must, so far as is reasonably practicable, monitor any conditions at the workplace that could put a worker’s health at risk. When work activities may expose workers to carbon

monoxide, WorkSafe recommends that the PCBU carries out exposure monitoring to determine the concentration of carbon monoxide in the workplace. If the PCBU is uncertain whether or not the concentration of carbon monoxide exceeds its workplace exposure standard (WES), they should carry out exposure monitoring.

Monitoring of workplace conditions should be carried out by, or under the supervision of,

a competent person who has sufficient knowledge, skills and experience in the appropriate techniques and procedures, including the interpretation of results (such as an occupational hygienists or other suitably trained personnel). They will compare the levels of carbon monoxide present in your workplace with the WES and can advise you whether you need to do more to manage the risk.

Monitoring should be undertaken regularly and after any significant change at the  workplace

to check the effectiveness of controls. If the controls are not working, seek advice on improving controls from an occupational health specialist.


Workplace Exposure Standards (WES)

Exposure to carbon monoxide should be controlled and the following WES should not be exceeded. You should review and, as necessary, revise control measures if the results of exposure monitoring show that the WES are being exceeded.

Exposure period



8 hours

25 ppm

average exposure over 8 hours

1 hour

50 ppm

average exposure over 1 hour

30 minutes

100 ppm

average exposure over 30 minutes

15 minutes

200 ppm

average  exposure over  15 minutes

Ceiling (instant)

400 ppm

Ceiling (instant) reading

Table 2: Carbon monoxide WES values


WES are intended to be used as guidelines by people qualified in occupational health practice. Further information on the interpretation of this WES should be sought from WorkSafe’s Workplace Exposure Standards and Biological Exposure Indices.


Monitoring worker health

PCBUs must, so far as is reasonably practicable, monitor any conditions at the workplace that could put a worker’s health at risk. There is no routine specified health monitoring for carbon monoxide exposure but a medical examination is recommended to identify those workers who may be more susceptible to carbon monoxide poisoning (ie history of coronary heart disease, anaemia, pregnancy).

PCBUs should get advice from an occupational health practitioner with experience in health monitoring before engaging in monitoring programmes or exposure control.

anyone who has been affected by carbon monoxide poisoning, even if they only have a headache, should see a doctor or go to the nearest hospital as soon as possible. a blood test should be carried out to determine if carbon monoxide poisoning has occurred. WorkSafe must be notified in cases where a person has been admitted to hospital for treatment.

To notify WorkSafe, phone 0800 030 040 or go to WorkSafe’s website to fill in or download a form.


What should you do in an emergency?

If someone at work seems to be affected by carbon monoxide poisoning, it’s important to ACT QUICKLY:

  • assess whether you can safely intervene, before attempting any action or rescue
  • make the situation safe by turning off the source
  • get the affected person outside – call 111
  • if it is impractical to move the affected person outside, ensure breathing apparatus is worn by rescuers
  • if there’s no heartbeat, begin CPR.

Anyone who has been affected by carbon monoxide poisoning, even if they only have a headache, must see a doctor or go to the nearest hospital as soon as possible.


For more information


[1] Carbon monoxide is measured in the atmosphere in parts per million (ppm).

Published: January 2017. Current until review in 2019.

Last updated 10 February 2017


On Monday 4 April 2016, the New Health and Safety at Work Act 2015 (HSWA) came into effect.

HSWA repeals the Health and Safety in Employment Act 1992, with immediate effect.

All references to the 1992 Act on this website and within our guidance will be progressively removed.