Carbon Monoxide (N3.7)

SECTION 2: Hazards identification

Main Hazards. All cylinders are portable gas containers, and must be regarded as pressure vessels at all times Carbon monoxide is a toxic, flammable gas. The flammability limits in the air are between 12,5% and 74,2% by volume. Inhaled carbon monoxide binds to the blood haemoglobin, greatly reducing the red blood cells ability to transport oxygen to body tissues. Effects may include headaches, dizziness, convulsions, loss of consciousness and death. Adverse Health effects. Carbon monoxide is a chemical asphyxiant, and the inhalation of concentrations as low as 400 ppm in air could result in headache and discomfort within 2 - 3 hours. Inhalation of concentrations of 4000 ppm in air could prove fatal in less than one hour. Chemical Hazards. Carbon monoxide containing moisture and sulphur- containing impurities can cause corrosion of steel at any pressure. Dry, sulphur- free carbon monoxide is safe for use with steel and other common metals at pressures up to 13790 kPa. Biological Hazards. Carbon monoxide in excess of 50 ppm will produce symptoms of poisoning if breathed in for a sufficiently long time. As little as 200 ppm will produce slight symptoms (slight headache, discomfort) in several hours. A concentration of 400 ppm will produce headache and discomfort within two to three hours. With moderate exercise, 1000 - 2000 ppm will produce slight palpitation of the heart in 30 minutes, a tendency to stagger in 1,5 hours, and confusion of the mind, headache, and nausea in 2 hours. A concentration of 2000 - 2500 ppm will usually produce unconsciousness in about 30 minutes. Its effects at higher concentrations may be so sudden that a man has little or no warning before he collapses. These effects are summarised in the following table. Effect Concentration (ppm) Permissible for an exposure of 8 hours 50 Concentration which can be inhaled for 1 hour without 400 - 500 appreciable effect Concentration causing a just appreciable effect after 1 600 - 700 hour of exposure Concentration causing unpleasant but not dangerous 1000 - 2000 symptoms after 1 hour of exposure Dangerous for exposure of 1 hour 1500 - 2000 Fatal in exposures of less than 1 hour 4000 & above Vapour Inhalation. The concentration, exposure time and physical activity of the individual will determine the percentage conversion of haemoglobin to carboxyhaemoglobin. The effects produced depend on the degree and duration of saturation of blood with carbon monoxide. The symptoms caused by various amounts of carboxyhaemoglobin in the blood are given in the following table. Blood Saturation % Symptoms Carboxyhaemoglobin 0 - 10 No symptoms. 10 - 20 Tightness across forehead, possibly slight headache. 20 - 30 Headache and throbbing in temples. 30 - 40 Severe headache, weakness, dizziness, dimness of vision, nausea, vomiting, collapse. 40 - 50 Same as previous item but with more possibility of collapse and syncope, increased respiration and pulse. 50 - 60 Syncope, increased respiration and pulse, Eye Contact No known effect. Skin Contact Ingestion No known effect.