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MedAir ENMET
Manual Release Date – June 9, 2017 P a g e | 34
Manual Part No. – 80002-042
Appendix A: CO Characteristics
The Characteristics and Effects of Carbon Monoxide
Carbon monoxide is a colorless odorless toxic gas generated by incomplete combustion of a hydrocarbon fuel in air. It may be present
where internal combustion engines, furnaces, boilers, and other combustion devices are present. It is toxic when inhaled because of its
great affinity to hemoglobin, the oxygen carriers in the red cells of the blood. CO replaces the oxygen normally carried by the
hemoglobin, and thus inhibits the delivery of oxygen throughout the body; the victim suffers from oxygen deficiency, and may die
from asphyxiation. The symptoms and degree of danger resulting from exposure to CO depend upon the concentration of the gas and
the length of exposure; this is shown in
Figure 10 . The M
ED
A
IR
2200 instrument is employed to warn the user of the presence of
CO, and to facilitate the assessment of the degree of danger that he or she is exposed to.
Based upon knowledge of the effects of CO, the Occupational Safety and Health Authority (OSHA) has set limits on exposure to CO
in the workplace. These are 35 ppm (parts CO per million parts air) as an time weighted average for an eight hour day, and a
maximum exposure of 200 ppm. For compressed air line applications, OSHA requires Grade D breathing air supplied, using a
Compressed Gas Association (CGA) definition (G-7.1). Depending on interpretation of the OSHA respiratory standard, 10 ppm and
20 ppm CO have been used as maximum limits and standard instrument alarm points.
If a CO sensor is installed, the
M
ED
A
IR
2200 has two preset alarm set points, at 10 ppm and 20 ppm CO, which are adjustable, but
cannot be set below 5 ppm or above 50 ppm.
The curves below are for percent Carboxyhemaglobin with 50% being the top curve, 5% the bottom. %COHb is a measure of the
amount of hemoglobin occupied by CO rather than oxygen. CO effects upon children, adults engaging in physical activity, and
smokers, are more pronounced.
Figure 10: Carbon Monoxide Concentration