[top] [end]What is carbon monoxide?
- Names: coal gas, coal fumes, wood gas, mine damp, white damp, carbon oxide, carbon monoxide
- Colorless, odorless, tasteless, non-corrosive, highly poisonous gas of about the same density as that of air.
- Very flammable, burning in air with bright blue flame.
- M.W. = 28.01; 42.88% C, 57.12% O
- Formula = CO. Although each molecule of CO has one carbon atom and one oxygen atom, it has a shape similar to that of an oxygen molecule (two atoms of oxygen), which is important with regard to it's lethality. Indeed, it is similar to two other gases necessary for life as we know it.
- Melting point = -205.0° C; Boiling point = -191.5° C
- Density = 1.250 g/liter at 0° C, 1 atm; 1.145 g/liter at 25° C, 1 atm
- Density (gas) = 0.968
- Soluble in some organic solvents such as ethyl acetate, methyl chloride, acetic acid; about 7 times more soluble in methanol and ethanol than in water.
- Flammable limits in air - 12-75 vol. %
[top] [end]When is CO produced?
CO is produced when: carbonaceous materials are burned with insufficient oxygen. Any fuel-burning appliance that is not adequately vented and maintained can become a potential source of CO. Worn or poorly adjusted and maintained combustion devices ( e.g. boilers, furnaces) can be significant sources, or a flue that is improperly sized, blocked, disconnected, or leaking. Auto, truck, or bus exhaust from attached garages, nearby roads, or idling vehicles in parking areas can also be a source.[top] [end]What are the Symptoms of CO Poisoning?
- Headache
- Fatigue
- Dizziness
- Paresthesias
- Chest pains
- Palpitations
- Visual Disturbances
[top] [end]Impacts on human health
At high concentrations CO exposure can be FATAL. Carbon monoxide exposures especially affect unborn babies, infants, and people with anemia or a history of heart or respiratory disease. Breathing low levels of CO can cause fatigue and increase chest pain in people with chronic heart disease. Breathing higher levels of carbon monoxide causes flu-like symptoms such as headaches, dizziness, and weakness in healthy people. Carbon monoxide also causes sleepiness, nausea, vomiting, confusion, and disorientation. At very high levels, it causes loss of consciousness and death.
[top] [end]What CO level are dangerous for the health?
The health effects of CO depend on the level of CO and length of exposure, as well as each individual's health condition. The concentration of CO is measured in parts per million (ppm). Health effects from exposure to CO levels of approximately 1 to 70 ppm are uncertain, but most people will not experience any symptoms. Some heart patients might experience an increase in chest pain. As CO levels increase and remain above 70 ppm, symptoms may become more noticeable (headache, fatigue, nausea). As CO levels increase above 150 to 200 ppm, disorientation, unconsciousness, and death are possible.
[top] [end]Why is it said to be fatal?
It takes very little CO in air to be deadly. This is because of the blood's enormous avidity for CO. It produces asphyxia. Hemoglobin (Hb) in the blood picks up oxygen molecules in the lungs and drops them off to the cells. The CO molecule can assume a shape so similar to oxygen that the hemoglobin can carry it as well (COHb). Hemoglobin has an affinity for CO that is about 250 times stronger than that for oxygen therefore it does not let go it .
The binding of CO to Hb also increases Hb's affinity for oxygen, so it does not let go of any oxygen it may be carrying either. This makes the situation worser than a comparable non-CO type of hypoxia.
Serious CO poisoning occurs when so much of the blood's hemoglobin is carrying CO that the cells don't get enough oxygen to survive. There also is evidence that the hypoxic effects of CO may involve a histotoxic component. CO binds to myoglobin and cytochromes inside cells which may critically limit cell metabolism by stopping the processes inside the cell that produce energy for cellular processes. Current research is examining this avenue of CO's action.
Most frequently CO poisoning occurs in the home as a result of faulty heating or cooking appliances. Automobile exhaust can cause CO poisoning in enclosed spaces such as garages, tunnels and parking garages. Smoking cigarettes raises the amount of CO in a smoker's blood stream, and may make him or her even more susceptible to environmental CO. Firemen are also at risk for CO poisoning from smoke inhalation.
[top] [end]What are the Allowable (Legal) Limits for CO?
- Occupational Safety & Health Administration, USA (OSHA) (for industrial situations) - Permissible Exposure Limit (PEL, by TWA) - 50 ppm, 8 hrs.
- Old PEL Standard (by TWA) - 35 ppm, 8 hrs.
- Threshold Limit Value (TLV, by TWA) - 25 ppm (29 mg/cu. m) (recommended by American Conference of Governmental & Industrial Hygienists [ACGIH]; Ceiling (max. value, 15 min.) - 200 ppm (229 mg/cu. m))
- Michigan Occupational Safety & Health Administration (MIOSHA) - PEL (Industry, by TWA) - 35 ppm, 8 hrs. (38.5 mg/cu. m); PEL (Construction, by TWA) - 50 ppm, 8 hrs. (55 mg/cu. m); Ceiling (max. value) - 200 ppm (229 mg/cu. m)
- Environmental Protection Agency, USA (EPA) - Domestic, outdoor air, all ages (TWA) - 9 ppm*, 8 hrs., Domestic, outdoor air, all ages (TWA) - 35 ppm, 1 hr.
- World Health Organization (WHO) - Domestic, outdoor air, all ages (TWA) - 9 ppm*, 8 hrs.
- American Gas Association - Indoor air (leakage at a heat register) - 15 ppm
- American Society of Heating, Refrigeration & Air Conditioning Engineers (ASHRAE) - Indoor air (leakage at a heat register) - 9 ppm
TWA - Computed by making measurements at intervals over 8 hours, then adding the sums of the concentrations and the intervals, and dividing by 8 hours (480 min.).
- Based on several published studies of people with coronary ischemic disease showing ECG changes during moderate exercise when breathing concentrations of CO giving 3% COHb.
[top] [end]How to measure carbon monoxide
- Digital display capable of measuring 1 - 2 ppm increments @ 5 - 10% accuracy (COMMENT)
- Scale to read at least up to 500 ppm.
- Reach 90% of final reading within one minute.
- Have a probe/hose assembly for flue gas sampling capable of withstanding high temperatures and the ability to remove water vapor from the combustion by-products.
- Ability for continuous sampling
[top] [end]Best Practices - CO Test Instruments
- CO test equipment can be affected by heat, cold, humidity, battery strength and mishandling.
- Always warm up and operate the instrument per manufacturer instructions.
[top] [end]Best Practices -Calibration of CO Testing Equipment
- Instruments must be calibrated per manufacturer instructions or when accuracy is in doubt.
- Field zeroing of the instrument should only be done with test gases as described in the owner's manual.
- Factory or other certified calibration must be performed at recommended intervals. Do not re-zero instruments for individual houses.
- Re-zeroing an instrument without test gases may result in readings that are not absolute or accurate.
- Zeroing of instruments should never be attempted on a job. Temperature, battery level, truck exhaust and other factors can affect zeroing.
- A constant need to zero indicates an instrument or operator error.
- Zeroing an instrument in the field eliminates reading the true ambient level.
[top] [end]Related topics
[top] [end]External links and references
- Carbon Monoxide (CO) Headquarters
- cofactsheet.htm
- data_General_Facts/carbonmonoxide-factsheet.pdf
- American Lung Association Fact Sheet on Carbon monoxide
- http://www.epa.gov/iaq/co.html
[top] [end]Contributors
- User:Dr Karabi Dutta 03 September 2003
- User:Grant Ballard-Tremeer 21 November 2003
Categories: Health| Carbon Monoxide