As evidenced in the graph, the national average CO concentrations have decreased substantially over the years. All BUT ONE tactic listed below has been utilized to reduce carbon monoxide emissions. That is:

Explanation:

Carbon monoxide (CO) is a colourless, non-irritant, odourless and tasteless toxic gas. It is produced by the incomplete combustion of carbonaceous fuels such as wood, petrol, coal, natural gas and kerosene. Its molecular weight is 28.01 g/mol, melting point −205.1 °C, boiling point (at 760 mmHg) −191.5 °C (−312.7 °F), density 1.250 kg/m3 at 0 °C and 1 atm and 1.145 kg/m3 at 25 °C and 1 atm, and relative density (air = 1) 0.967 (1,2). Its solubility in water at 1 atm is 3.54 ml/100 ml at 0 °C, 2.14 ml/100 ml at 25 °C and 1.83 ml/100 ml at 37 °C.

The molecular weight of carbon monoxide is similar to that of air (28.01 vs approximately 29). It mixes freely with air in any proportion and moves with air via bulk transport. It is combustible, may serve as a fuel source and can form explosive mixtures with air. It reacts vigorously with oxygen, acetylene, chlorine, fluorine and nitrous oxide. Carbon monoxide is not detectable by humans either by sight, taste or smell. It is only slightly soluble in water, blood serum and plasma; in the human body, it reacts with haemoglobin to form carboxyhemoglobin (COHb).

The relationship of carbon monoxide exposure and the COHb concentration in blood can be modelled using the differential Coburn-Forster-Kane equation (3), which provides a good approximation to the COHb level at a steady level of inhaled exogenous carbon monoxide.

Conversion factors

At 760 mmHg and 20 °C, 1ppm = 1.165 mg/m3 and 1 mg/m3 = 0.858 ppm; at 25 °C, 1 ppm = 1.145 mg/m3 and 1 mg/m3 = 0.873 ppm.