Carbon Monoxide

Carbon Monoxide :

What is Carbon Monoxide (CO):

Carbon Monoxide (also known as CO) is a colorless, odorless poisonous gas and is a common yet preventable cause of death from poisoning worldwide. Approximately half of the deaths from unintentional CO poisonings result from the inhalation of smoke from fires. Other significant causes are vehicle exhausts and deaths in industrial / commercial settings. On average between 1 and 2 people die each year in Ireland from unintentional CO poisoning in the home in incidents related to domestic heating or other fossil fuel installations in the home (i.e. excluding the inhalation of smoke from fires).

The incomplete combustion of organic fossil fuels such as oil, gas or coal is a common environmental source of CO and is responsible for many cases of non-fatal unintentional CO poisoning.

In normal conditions the combustion process (the addition of oxygen) will result in carbon in the fossil fuel, combining with oxygen, in the air, to produce Carbon Dioxide (CO2), the same substance we exhale when we breathe.

However, if there is a lack of air for the combustion process or the heating appliance is faulty, Carbon Monoxide can be produced.

When CO is inhaled into the body it combines with the blood, preventing it from absorbing oxygen. If a person is exposed to CO over a period, it can cause illness and even death.

Carbon Monoxide has no smell, taste or colour. This is why it is sometimes called the "Silent Killer".

Carbon Monoxide alarms can be used as a backup to provide a warning to householders in the event of a dangerous build up of CO. Check that the Carbon Monoxide alarm complies with the EN 50291 standard. Remember that Carbon Monoxide alarms are no substitute for regular inspection and maintenance of appliances, vents, flues and chimneys.

There are signs that you can look out for which indicate incomplete combustion is occurring and may result in the production of CO:

  • yellow or orange rather than blue flames (except fuel effect fires or flueless appliances which display this colour flame).
  • soot or yellow/brown staining around or on appliances.
  • pilot lights that frequently blow out.
  • increased condensation inside windows

There are a number of simple steps that gas consumers can take to keep themselves safe.

Carbon monoxide can be produced by any combustion appliance, including those that burn fossil fuels e.g. oil, wood and coal.  If you have one of these appliances you should make sure that it is serviced and maintained by a competent person and the chimney is regularly swept.

Carbon Monoxide Poisoning:

Causes of CO Poisoning:

You can be in danger of Carbon Monoxide poisoning at home if dangerous amounts of Carbon Monoxide accumulate in the home. This can happen as a result of any or a combination of the following:

  • Faulty or damaged heating appliances
  • Heating appliance not maintained or serviced
  • Rooms not properly ventilated
  • Blocked chimneys or flues
  • Indoor use of a barbecue grill or outdoor heater
  • Poor installation of heating appliances
  • Improper operation of heating appliances
  • Property alterations or home improvements, which reduce ventilation
  • Running engines such as vehicles or lawnmowers in garages
  • Using cooking appliances for heating purposes

High level CO poisoning results in progressively more severe symptoms, including:

  • Mental confusion
  • Vomiting
  • Loss of muscular coordination
  • Loss of consciousness
  • Ultimately death

Where is CO found?

Natural sources of CO such as forest fires create the largest amount of CO worldwide, but human made sources such as internal combustion engines are a greater concern to workers. This is because they can produce localized high-hazard areas, particularly in confined spaces or areas where there is poor ventilation.

Potential sources of CO include emissions from:

  • Vehicles
  • Portable generators
  • Gasoline-powered tools (for example, chop saws)
  • Fires and explosions
  • Natural gas space heaters
  • Kilns, furnaces, and boilers
  • Welding
  • Cigarette smoking

Tobacco smoking can be as much of a CO hazard to workers who smoke as work-related exposure. Smoking produces COHb levels 10-20 times the normal low levels produced by breathing city air. Tobacco smoke contains 4-6% of CO (40,000-60,000 ppm). This CO is diluted in the mouth and upper airways, but the remaining 400 ppm that is inhaled is still a very large amount. Workers who smoke put themselves at higher risk of serious harm if they are also exposed to CO in their jobs.

Symptoms of CO Poisoning:

Symptoms of Carbon Monoxide poisoning can be similar to those caused by other illnesses such as a cold or flu. They include

  • headaches or dizziness
  • breathlessness
  • nausea
  • loss of consciousness
  • tiredness
  • pains in the chest or stomach
  • erratic behavior
  • visual problems

What to Do?

If anyone in your house has any of the symptoms outlined above get fresh air immediately, then go to your doctor and ask him/her to check for Carbon Monoxide poisoning.

Stop using the appliance immediately & do not use it again until it has been checked by a registered installer or a qualified service agent.

The amount of CO which the blood absorbs depends chiefly on two things: how much CO is in the air and the time of the exposure. Adverse effects of CO on humans are reduced by periods of breathing fresh air. The degree of recovery depends on the number and length of those periods. The general state of health and degree of physical activity of a person exposed to CO are other factors involved in the effects of Carbon Monoxide on the body.

Physiological Effects of Carbon Monoxide (CO):

Know the Danger Signs:

Watch out for any of the warning signs that your appliance is not functioning properly:

  • Staining, scooting or discoloration around the appliance.
  • Appliances that burn slowly, badly (orange or 'floppy' flames) or go out.
  • A yellow or orange flame where normally blue.
  • Condensation or dampness on walls and windows in the room once the appliance is lit.
  • A strange smell when the appliance is on.
  • Rusting or water streaking on appliance cabinet/vent/chimney.
  • Loose or disconnected vent/chimney connections or guards

Advice on Appliances:

Oil, Gas and Solid fuel Appliances

When buying an oil or gas appliance, deal with a reputable outlet. Every new appliance is supplied with a full instruction book, essential to the correct and safe use of the appliance. Insist that the appliance installer gives you an instruction book. Read it carefully and get to know your appliance. Keep the instructions handy. If you are moving house leave the instruction book for any appliance you are not taking with you (contact your appliance supplier if you need a replacement instruction book).

All appliances should be serviced and checked for safety annually to make sure they are working safely and efficiently. If you're concerned that an appliance is not operating safely, or that the installation in your house is not in good condition or unsafe then have a safety inspection conducted.

Mobile Gas Heaters (L.P.G.)

The use of mobile heaters which are damaged can result in the production of Carbon Monoxide. In particular if the plaques or bricks at the front of the heater are damaged, or the retaining cement is missing, they should be immediately replaced by a competent person. The heater should not be used in a damaged condition. For further details on safety checks for mobile gas heaters.

Safety alert on New World Vision gas cookers

The New World Vision 50TWLMSV (LPG) gas cooker can produce dangerous levels of carbon monoxide if not operated in accordance with the manufacturer's instructions. For further information on this and other New Wold Vision 50TWL models affected and the required safety actions.

Wood Pellet Boilers

Wood Pellet Boilers are commonly used in homes and businesses as an alternative to the oil or gas fired boilers. Wood pellets, the fuel source for these units are normally housed in a large sealed hopper/tank that is either fitted with screw feeder (auger) connected to the boiler, or the hopper/tank is mounted over the boiler for gravity feeding. Due to the enclosed nature of these hoppers/tanks the atmosphere inside can become oxygen depleted and a toxic atmosphere can accumulate. All operators, maintenance personnel and users of this equipment need to ensure the following;

  1. DO NOT ENTER or place your head into the wood pellet hopper under any circumstances. The unit can contain toxic gases.
  2. Ensure that your wood pellet hopper/tank and boiler has been installed and commissioned by a competent person. If in doubt, contact the supplier and/or manufacturer and request assistance.
  3. Ensure that the boiler is cleaned and serviced by a competent person at the frequency required by the manufacturers’ instructions.
  4. If any problems are encountered with the unit, such as, system not heating correctly, flue gas is flowing into boiler room, turn unit off and seek assistance immediately.
  5. No personnel should enter the hopper/tank unless fully trained and competent in confined space entry procedures. The hopper/tank should be fully ventilated and controls put in place to ensure safe entry as per the HSA Code of Practice “Safe Work in Confined Spaces”.
  6. Ensure boiler room is well ventilated at all times to ensure no inadvertent build up of toxic gases.

Installing a carbon monoxide alarm could save your life

Regular inspection and maintenance of appliances, vents, flues and chimneys are the best ways to protect you and your family from the hidden danger of carbon monoxide. For added protection install an audible carbon monoxide alarm.

Carbon Monoxide alarms are available from many hardware and DIY stores.

There are some points you need to be aware of to make sure your alarm effectively protects you.

What type should I use?

Many different alarms are available but we recommend that the alarm;

  • Complies with European Standard EN 50291 - This should be marked on the box
  • Carries the CE Mark
  • Has an 'end of life' indicator - This indicator should not be confused with any 'fault' indicator
  • Carries an independent certification mark – For example a kite mark, this indicates that the alarm has been approved by an accredited testing and certification organization.

One alarm may not be sufficient

If all your fuel-burning appliances (including their exhaust flues and air supplies) are in the one room, then one alarm in that room may suffice. If the appliances/flues are located in more than one room, then an alarm should be fitted in each of those rooms.

Always follow the manufacturer's guidelines when installing alarms or have a qualified installer fit it for you.

Make sure the alarm can be heard

If the alarm(s) cannot be heard in any living rooms and in all bedrooms, more advanced alarms that include the provision for interconnecting them can be used. In this case, if one interconnected alarm detects CO, it will trigger the other units to also sound an alarm. This allows you to position extra alarms close to the living rooms and bedrooms, where they will be audible.

Safety Precautions:

  • Ensure your appliances are correctly installed and SERVICED ANNUALLY.
  • Ensure that rooms in your home containing heating appliances are properly ventilated - NEVER BLOCK VENTS.
  • Make sure all chimneys are regularly swept and kept clear.
  • Use appliances only for the PURPOSE for which they were designed, e.g. do not use a cooker to heat a room.
  • NEVER use any appliance if you suspect it might be faulty.
  • If undertaking ALTERATIONS to your home which may affect the safety or efficiency of your heating installation (e.g. adding an extension, converting a garage, removing internal walls, changing a living room into a bedroom, double glazing / weather sealed doors) follow this safety advice:
    • Do not block or build around any existing air vents or flues.
    • If creating a new living space, ensure it has ventilation in accordance with Building Regulations.
    • If adding additional radiators ensure that your boiler can cope with the additional capacity
    • If you are altering or adding appliances to a natural gas or LPG installation, ensure that work is carried out to IS813:2002 Domestic Gas Installations.
    • Get professional advice on ventilation and fueling before embarking on alterations to your house. Contact your fuel supplier for details of qualified personnel.
  • Use Carbon Monoxide alarms but remember these are no substitute for regular inspection and maintenance of appliances, vents, flues and chimneys. Check that the Carbon Monoxide alarm complies with the EN 50291 standard.

Natural Gas:

Choose room-sealed appliances. With room-sealed appliances fresh air intake for combustion comes from outside of the house and emissions are then discharged outside also. As such, the air in the room where the appliance is fitted is not used or affected by the appliance. There fore room sealed appliances (balanced flue or fanned drought types) are recommended for new and replacement boilers and water heaters.

Do you have an unsafe water heater?

Flue less gas water heaters are considered dangerous because they consume the air inside the room. This causes the products of combustion - including toxic Carbon Monoxide - to discharge directly into the room where the heater is fitted. If used for extended periods, the levels of Carbon Monoxide can build up to dangerous levels if there is a lack of ventilation. Open flue-type water heaters located in bathrooms are also considered unsafe.

Clinical Effects

The stakes for diagnosing and treating CO poisoning are high. Fast, effective treatment can do much to improve clinical outcomes and contain damage to the neurological, cardiac, metabolic, pulmonary and renal systems of the body as described.

Impact of CO Poisoning on the Body Systems:


CO poisoning causes central nervous system depression presenting in a host of impairments. In mild cases, patients report headaches, dizziness and confusion. In severe cases, patients may be comatose or develop seizures. Long-term neurocognitive and neuropsychiatric sequel are reported even after moderate to severe single exposures.


CO poisoning causes decreased myocardial function and dilatation and a decreased oxygen delivery to, and utilization of, oxygen by the myocardium. As a result, the patients may present hypertensive or with tachycardia, chest pain, arrhythmia or myocardial ischemia. Most deaths from CO poisoning ultimately result from ventricular arrhythmia.7 Long-term cardiac sequel are reported even after moderate to severe single exposures, increasing the odds ratio of premature cardiac death.


Respiratory alkaloids (hyperventilation) is possible in mild cases. With severe exposure, metabolic acidosis may result in elevated levels of acid throughout the body.


Pulmonary edema occurs in 10 – 30 percent of acute CO exposures.7 This may be due to a direct effect on the alveolar membrane, left ventricular failure, aspiration or neurotic pulmonary edema.

Multiple Organ Failure

At high levels, multiple organ failures are expected, with a lethal outcome likely without immediate treatment to remove the CO.

Exposure Levels and OSHA Air Quality:

The Occupational Safety and Health Administration (OSHA) permissible exposure limit for carbon monoxide is 50 ppm of air, or 55 milligrams per cubic meter (mg/m3) as an eight-hour time-weighted average concentration. The National Institute for Occupational Safety and Health (NIOSH) recommends exposure levels (REL) below the OSHA air-quality numbers. They recommend keeping exposure to less than 35ppm, or 40 mg/m3 in eight hours. The ACGIH has assigned a carbon monoxide threshold-limit value (TLV) of 25 ppm or 28.6 mg/m3 for eight hours.

CO risk factors

The following factors may increase the risk of workers being exposed to unsafe levels of CO:

  • Confined or enclosed spaces - Toxic levels of CO can quickly build up where ventilation is poor and combustion of carbon-containing materials occurs. This is particularly dangerous during winter months in locations such as garages or construction sites, where ventilation is further reduced as windows and doors are closed to conserve heat (or propane heaters are used).
  • Tobacco smoking - Smoking raises the level of COHb in the blood as well as causing lung disease. Smoking a pack of cigarettes a day may produce a COHb level of 5% in the blood. Three packs a day may produce a level of 9%. Exposure to CO on the job in addition to smoking can quickly produce toxic effects.
  • Pre-existing medical conditions - Chronic lung and cardiovascular disease and severe anemia can limit the amount of oxygen carried into the blood to the tissues.
  • Worker training - Workers are more likely to be harmed if they don't know the hazards of CO.

Reducing the CO risk

The risk of unsafe levels of CO can be reduced with the following controls:

  • Engineering - Increase the efficiency of burning processes, repair leaks in burners, switch from petroleum to electric energy when risk is high, and use catalytic converters on engine exhaust.
  • Ventilation - Prevent the buildup of CO through the proper design of general ventilation for enclosed spaces and the use of properly designed local exhaust ventilation systems (such as tailpipe exhaust systems).
  • Isolation controls - Isolate workers from dangerous work areas.
  • Monitoring - CO levels must be monitored where there is a risk of CO exposure.
  • Education - Workers must be taught how to prevent and recognize CO poisoning, and how to give first aid to those overcome by the gas.
  • Labeling and posting - Post appropriate warning signs in areas where significant exposures to CO are likely to occur.
  • Stop smoking - Cut down on smoking or quit entirely to reduce the personal hazard from CO on the job.

First aid and rescue

In the event of a poisoning, follow these guidelines:

  • Summon the first aid attendant for your work site as outlined in the posted written procedures for providing first aid.
  • To attempt a rescue in an area with high CO levels, wear only a positive-pressure, self-contained breathing apparatus (SCBA), or a full-face, supplied air (airline) respirator with an "escape" air bottle.
    Note: Only qualified personnel should attempt a rescue.
  • If your work site does not require a first aid attendant, follow these steps:
    • Move the poisoned worker to fresh air.
    • Keep the worker warm and at rest. Activity may worsen the effects of CO by increasing oxygen demand.
    • If available, give 100% oxygen through a tight-fitting mask. Oxygen therapy should be continued for at least two hours—it takes 80 minutes to get rid of half of the CO in the body when breathing 100% oxygen.
    • If the worker is having trouble breathing or is not breathing, start assisted ventilation using a pocket mask. Add oxygen to the mask, if available. If the worker has no pulse, begin cardiopulmonary resuscitation (CPR). Because the body rids itself of CO when removed from the exposure, it is critical to continue giving the worker assisted ventilation with oxygen until medical aid arrives.
    • Call for a doctor or get the worker to a hospital while continuing first aid treatment.

Treatment must begin right away—delay is a significant factor in permanent brain damage.

Workers who are accidentally exposed to CO usually recover fully, if the exposure has not caused unconsciousness. It's a good idea to see a doctor before returning to work because weakness or lack of coordination may lead to accidents.

The Quiet killer -Carbon Monoxide

Where to install CO Alarm