Carbon Monoxide Poisoning from Heaters and Stoves

Why does carbon monoxide go unnoticed?

Carbon monoxide (CO) is produced when fuels such as coal, wood, natural gas, LPG, petrol and diesel burn with insufficient oxygen, in other words without complete combustion. It has no colour, smell or taste; it does not sting the eyes or cause coughing. When inhaled, it binds to haemoglobin, which carries oxygen in the blood, about 200 times more strongly than oxygen does, and reduces the oxygen reaching the tissues. The organs most affected are those most sensitive to oxygen: the brain and the heart.

Carbon monoxide poisoning at work is mostly seen in the winter months, outside working hours and during sleep. A sleeping person can lose consciousness before noticing the symptoms. That is why prevention should rely not on the assumption "we'd smell it", but on controlling the source and on a detector. For other aspects of preparing for winter, such as icing and the fire risk of temporary heaters, see our article on workplace safety in the winter months.

Where does carbon monoxide poisoning occur at work?

In Bursa and the surrounding provinces, the riskiest places in winter are small spaces where people stay overnight:

For work equipment the rule is clear: mobile work equipment with an internal combustion engine may be used in work areas only on condition that sufficient air is provided so as not to create a health and safety risk for workers (Work Equipment Regulation Annex II item 2.5). In confined spaces such as tanks, wells and manholes, engine exhaust is additionally lethal; for this work, see the permit rules in our article on working in confined spaces.

Carbon monoxide symptoms: flu or poisoning?

Mild CO poisoning is easily confused with a cold or tiredness. Carbon monoxide symptoms progress according to severity as follows:

• Early stage: Headache, dizziness, nausea, weakness, drowsiness.
• Later stage: Vomiting, clouded consciousness, chest pain, palpitations, shortness of breath, loss of coordination.
• Severe picture: Fainting, seizures, loss of consciousness and death.

Clues that should point to poisoning:

• Similar complaints at the same time in more than one person in the same space.
• Complaints getting worse in the room where the heater is burning and easing on going outside.
• A headache that starts on waking in the morning and eases during the day.

Pregnant workers and those with heart and lung disease can be affected by lower exposures; the workplace physician assesses these workers separately. Because problems with attention, memory and movement can appear days or weeks later in people who have suffered severe poisoning, return to work should be planned with the physician's assessment.

Heating with braziers and stoves: rules at work

Heating with a brazier at work is not a safe method under any circumstances; a stove can be used only if it is correctly installed and operated under a monitored arrangement. Most cases of stove poisoning start with one of the following rules being broken:

1. Braziers are not lit indoors. A brazier that has burned down to embers keeps producing CO; a brazier brought indoors because "the smoke has gone" is the most dangerous of all.
2. A stove is used only where there is a flue. Pipe connections must be leak-tight, the slope correct and the top of the flue open. The fresh air inlet must not be blocked where the stove is located.
3. Take care in windy weather. When the flue draught is disrupted, smoke and gas can come back into the room; if complaints start, the stove is put out.
4. The stove is not left burning overnight, especially in sleeping containers. Filling the stove to the top and turning down its air supply prevents complete combustion and increases CO production.
5. Generators and engine-driven equipment are run outdoors; the exhaust is directed away from doors and windows.
6. Heating that produces no combustion products is preferred. An electric heater does not produce CO but does carry a fire risk: a fixed socket instead of an extension cable, distance from combustible materials and a rule to switch it off at the end of the working day are applied.

Turning these rules into a written instruction and posting it on container and hut doors is important, especially on sites where shift and subcontractor teams work. To add these items to site checks, see our article on the construction site OHS checklist.

CO detectors: selection and placement

A CO detector measures carbon monoxide in the air and gives an audible alarm before it reaches a dangerous level. It should be present in every enclosed space where a stove, gas heater or generator is used, and especially in containers and huts where people sleep.

• Standard: Choose a CE-marked device conforming to EN 50291 for dwellings and similar living spaces. A smoke detector does not detect CO; they are separate devices, although some models combine both.
• Location: Following the manufacturer's instructions, position it in the room where the combustion appliance is located and in the sleeping area. Do not place it directly above the stove, right next to a window or ventilation opening, behind a curtain or inside a cupboard.
• Testing and maintenance: Check it regularly with the test button; keep track of battery replacement and the device's service life. Sensor-based devices have a limited life.
• Alarm instruction: What to do when the alarm sounds should be written on the inside of the door: put out the heater, open the door and window, get everyone outside, call 112 if anyone has symptoms, inform the person in charge.

A detector is a warning device and is no substitute for prevention. Nobody should sleep again in a space where the alarm has gone off until the source has been found and eliminated.

First response steps

1. Protect yourself: Open the door and window before entering. If you need to go in, keep it brief and have a second person wait outside.
2. Stop the source: If it is safe, switch off the heater and close the gas valve.
3. Take the person out into fresh air: Let them rest without making them walk or exert themselves, and keep them from getting cold.
4. Call 112: Be sure to say that there is a heater or engine in the space and that carbon monoxide is suspected.
5. If they are unconscious: If they are breathing, place them on their side; if they are not breathing, a trained first aider starts basic life support.
6. Go to hospital even if the symptoms pass: Treatment involves oxygen; in severe cases hyperbaric oxygen therapy may be needed.

The number of first aiders is one for every 20 workers in less hazardous, every 15 in hazardous and every 10 in very hazardous workplaces, and the certificate is valid for 3 years; for details, see our article on the first aid certificate.

Poisoning that occurs at the workplace or because of the conduct of work and affects a worker's health may fall within the definition of a workplace accident in the Law. In that case the incident is recorded and notified to the SGK (Social Security Institution) within 3 working days after the accident (Law No. 6331 Art. 14/2). For the process, see our article on what to do after a workplace accident.

Including it in the emergency plan and risk assessment

• Risk assessment: Write the heating method, fuel type and the list of containers and huts as separate rows; review these rows before winter.
• Emergency plan: Add the CO poisoning scenario to the plan with first response and evacuation steps; designate contacts for night watchmen and those staying in sleeping quarters. Under our emergency plan service we prepare this scenario according to the layout of the site and the facility.
• Briefing: At the start of winter, hold a short briefing, especially with staff who stay in the sleeping quarters and work at night; show the brazier ban and the alarm instruction on site.
• Health surveillance: The follow-up and return to work of a worker who has been poisoned are handled with the physician's assessment under our workplace physician service.

For general obligations in construction work, see our article on the OHS regulation for construction work, and for our approach to building sites, our construction sector page.

Frequently Asked Questions

What are the symptoms of carbon monoxide poisoning?

Early symptoms are headache, dizziness, nausea, weakness and drowsiness; as it progresses, vomiting, clouded consciousness, chest pain and loss of consciousness are seen. Similar complaints in more than one person in the same space, and relief on going outside, should point to poisoning.

Can a stove be used in a site container?

Only with a correctly connected flue, an open fresh air inlet and an arrangement under which it is not left burning overnight; there should be a CO detector in the container. A brazier, however, should not be used in an enclosed container under any circumstances. Where possible, electric heating connected to a fixed socket, which produces no combustion products, should be preferred.

Where should a CO detector be fitted?

Following the manufacturer's instructions, it should be fitted in the room where the combustion appliance is located and in the sleeping area. Places such as directly above the stove, right next to a window or ventilation opening and inside a cupboard distort the measurement. The device should be tested regularly, and its battery and service life tracked.

Does carbon monoxide poisoning count as a workplace accident?

Poisoning that occurs at the workplace or because of the conduct of work and affects a worker's health may be assessed as falling within the definition of a workplace accident in the Law. In that case the incident is recorded, investigated and notified to the SGK within 3 working days after the accident.