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DESIGNATIONS
CAS No.: 630-08-0
Registry name: Carbon monoxide
Chemical name: Carbon monoxide
Synonyms, Trade names: Carbon oxide, carbon(II) oxide
Chemical name (German): Kohlenmonoxid, Kohlenoxid
Chemical name (French): Oxyde de carbone, monoxyde de carbone
Appearance: colourless, odourless gas
BASIC CHEMICAL AND PHYSICAL DATA
| Empirical formula: | CO | ||
| Rel. molecular mass: | 28.01 g | ||
| Density: | 1.25 g/l at 0°C | ||
| Relative gas density: | 0.97 | ||
| Boiling point: | -191.5°C | ||
| Melting point: | -199°C | ||
| Ignition temperature: | 605°C | ||
| Explosion limit: | 12.5 - 74 vol.% | ||
| Max. explosion pressure: | 7.3 x 105 Pa | ||
| Odour threshold: | none | ||
| Solvolysis/solubility: | in water: | 33 ml/l | (at 0°C) |
| 23 ml/l | (at 20°C) | ||
| soluble in ethyl acetate, chloroform, glacial acetic acid, ethyl acetate and other organic solvents | |||
| Conversion factors: | 1ppm = 1.164 mg/m3 | ||
| 1 mg/m3 = 0.859 ppm | |||
ORIGIN AND USE
Usage:
The most important use of CO in production involves its reaction
with steam at elevated temperature to form syngas which is e.g.
used to produce methanol. Carbon monoxide is also used in the
reduction of oxides to form pure metals. It is, however, used on
a very small scale.
Origin/derivation:
Carbon monoxide is an unwanted by-product of numerous thermal
processes. It is produced in the course of all
oxygen-undersaturated combustion processes involving carbon and
its compounds. The natural sources of carbon monoxide predominate
(90% of total emissions); the remaining 10% are made up of
motor-vehicle emissions (55%), industry (11%) and other emitters
(HORN, 1989).
Carbon monoxide is a component of "town gas".
Toxicity
| Humans: | LCLo 4,000 ppm, inhalation (30 min) | acc. UBA, 1986 |
| TCLo 650 ppm, inhalation (45 min) | acc. UBA, 1986 | |
| Mammals: | ||
| Rat: | LC50 1,807 ppm, inhalation (4 h) | acc. UBA, 1986 |
| Mouse: | LC50 2,444 ppm, inhalation (4 h) | acc. UBA, 1986 |
| Cat: | MLC 10,040 mg/m3, inhalation (35 min) | acc. HORN, 1989 |
| Guinea pig: | LC50 2,811 mg/m3, inhalation (4 h) | acc. HORN, 1989 |
| Aquatic organisms: | ||
| Fish: | LD > 1.2 mg/l | acc. UBA, 1986 |
Characteristic effects:
Humans/mammals: The toxicity in humans and animals is caused by the extraordinary affinity of carbon monoxide for haemoglobin which is responsible for the oxygen transport (approx. 250 times greater affinity of carbon monoxide compared to oxygen [ULLMANN/RÖMPP]). Intake is exclusively by way of inhalation. Carbon monoxide cannot be perceived on the basis of odour, colour, taste, irritation of the mucous membranes or other effects. Thus, poisoning due to town gas or vehicle emissions may take place (frequently suicide results).
Acute poisoning takes the form of headaches, retching, muscular weakness, loss of consciousness, shortness of breath and finally death, depending on the concentration and time of exposure.
Plants: Carbon monoxide does not poison plants since it is rapidly oxidised to form carbon dioxide which is used for photosynthesis.
ENVIRONMENTAL BEHAVIOUR
Water:
Carbon monoxide is only slightly soluble in water. Depressurizing
the compressed gas quickly leads to the formation of explosive
mixtures over the surface of the water. Carbon monoxide is listed
under water hazard class 0 in the Federal Republic of Germany (no
hazard to water). It has a toxic effect on fish.
Air:
Carbon monoxide is about as dense as air. It ingresses into the
atmosphere by way of exhaust gases and is rapidly oxidised to
form carbon dioxide. The substance is particularly hazardous
because of ist widespread dispersion and the high toxicity level
for humans and animals. Particular attention is therefore to be
paid to the CO concentration in breathing air in smog areas.
Soil:
Oxygen-undersaturated soils have been found to have a higher
concentration of carbon dioxide oxidised from carbon monoxide. CO
accelerates the oxidation of NO to form NO2. Roughly
80 t CO/km2 are converted every year by soil bacteria.
Half-life:
The dwell time of CO in the atmosphere is between 1 and 2 months
on average (HORN, 1989). The half-life of carbon monoxide bonded
in blood is about 250 minutes (HORN, 1989).
Degradation, decomposition products:
Carbon monoxide rapidly oxidises to form carbon dioxide.
Especially at higher temperatures, it reacts explosively with
numerous substances (e.g. aluminium dust, potassium, nitrogen
dioxide) with heat being produced (e.g. bromine trifluoride,
silver oxide). Plants metabolise CO to form CO2 or
methane.
Food chain:
There is no evidence of residues in foodstuffs or semi-luxury
goods. Smokers inhale considerable quantities of carbon monoxide
in cigarette smoke.
ENVIRONMENTAL STANDARDS
| Medium/ acceptor | Sector | Country/ organ. | Status | Value | Cat. | Remarks | Source |
| Air: | AUS | (L) |
30 ppm | 2 h | acc. STERN, 1986 | ||
| AUS | (L) |
10 ppm | 8 h | acc. STERN, 1986 | |||
| B | (L) |
6 mg/m3 | 8 h | acc. MEINL et al., 1985 | |||
| B | (L) |
15 mg/m3 | 1 h | acc. MEINL et al., 1985 | |||
| BG | (L) |
3 mg/m3 | 30 min1) | acc. STERN, 1986 | |||
| BG | (L) |
1 mg/m3 | 24 h1) | acc. STERN, 1986 | |||
| CH | (L) |
8 mg/m3 | 24 h | acc. BUB, 1986 | |||
| CDN | (L) |
35 mg/m3 | 2 h | acc. STERN, 1986 | |||
| CDN | (L) |
15 mg/m3 | 8 h | acc. STERN, 1986 | |||
| CS | (L) |
6 mg/m3 | 30 min | acc. STERN, 1986 | |||
| CS | (L) |
1 mg/m3 | 24 h | acc. STERN, 1986 | |||
| D | L |
10 mg/m3 | MIK | Long-time value2) | acc. BAUM, 1988 | ||
| D | L |
50 mg/m3 | MIK | Short-time value3) | acc. BAUM, 1988 | ||
| D | L |
10 mg/m3 | IW 1 | acc. TA Luft, 1986 | |||
| D | L |
30 mg/m3 | IW 2 | acc. TA Luft, 1986 | |||
| DDR | (L) |
3 mg/m3 | MIKD | acc. HORN, 1989 | |||
| DDR | (L) |
5 mg/m3 | MIKK | acc. HORN, 1989 | |||
| E | (L) |
45 mg/m3 | 30 min | acc. STERN, 1986 | |||
| E | (L) |
15 mg/m3 | 8 h | acc. STERN, 1986 | |||
| GB | (L) |
10 mg/m3 | 8 h | acc. BUB, 1986 | |||
| GB | (L) |
40 mg/m3 | 1 h | acc. BUB, 1986 | |||
| GR | (L) |
15 mg/m3 | 8 h, smog warning | acc. MEINL et al., 1985 | |||
| GR | (L) |
25 mg/m3 | 8 h, smog alarm stage 1 | acc. MEINL et al., 1985 | |||
| GR | (L) |
35 mg/m3 | 8 h, smog alarm stage II | acc. MEINL et al., 1985 | |||
| H | (L) |
1 mg/m3 | 30 min5) | acc. STERN, 1986 | |||
| H | (L) |
3 mg/m3 | 30 min1) | acc. STERN, 1986 | |||
| H | (L) |
6 mg/m3 | 30 min6) | acc. STERN, 1986 | |||
| I | (L) |
40 mg/m3 | 2 h | acc. STERN, 1986 | |||
| I | (L) |
10 mg/m3 | 8 h | acc. MEINL et al., 1985 | |||
| IL | (L) |
30 ppm | 30 min | acc. STERN, 1986 | |||
| IL | (L) |
10 ppm | 8 h | acc. STERN, 1986 | |||
| J | (L) |
10 ppm | 24 h | acc.STERN, 1986 | |||
| J | (L) |
20 ppm | 8 h | acc. STERN, 1986 | |||
| J | (L) |
58 mg/m3 | 1 h, priority stage II | acc. MEINL et al., 1985 | |||
| N | (L) |
25 mg/m3 | 3 h | acc. STERN, 1986 | |||
| N | (L) |
10 mg/m3 | 8 h | acc. STERN, 1986 | |||
| NL | (L) |
40 mg/m3 | 2 h | acc. STERN, 1986 | |||
| NZ | (L) |
30 ppm | 2 h | acc. STERN, 1986 | |||
| NZ | (L) |
10 ppm | 24 h | acc. STERN, 1986 | |||
| RC | (L) |
1 ppm | 60 min | acc. STERN, 1986 | |||
| RP | (L) |
30 ppm | 2 h | acc. STERN, 1986 | |||
| RP | (L) |
9 ppm | 8 h | acc. STERN, 1986 | |||
| SA | (L) |
40 mg/m3 | 2 h | acc. STERN, 1986 | |||
| SA | (L) |
10 mg/m3 | 8 h | acc. STERN, 1986 | |||
| SF | (L) |
40 mg/m3 | 2 h | acc. STERN, 1986 | |||
| SF | (L) |
10 mg/m3 | 8 h | acc. STERN, 1986 | |||
| SU | (L) |
3 mg/m3 | 30 min1) | acc. STERN, 1986 | |||
| TJ | (L) |
6 mg/m3 | 6 min | acc. STERN, 1986 | |||
| TJ | (L) |
2 mg/m3 | 24 h | acc. STERN, 1986 | |||
| WHO | G |
10 mg/m3 | 8 h | acc. UBA, 1988 | |||
| WHO | G |
30 mg/m3 | 1 h | acc. UBA, 1988 | |||
| WHO | G |
60 mg/m3 | 1/2 h | acc. UBA, 1988 | |||
| YU | (L) |
10 mg/m3 | 30 min3) | acc. STERN, 1986 | |||
| YU | (L) |
30 mg/m3 | 30 min4) | acc. STERN, 1986 | |||
| YU | (L) |
40 mg/m3 | 1 h | acc. STERN, 1986 | |||
| YU | (L) |
10 mg/m3 | 8 h | acc. STERN, 1986 | |||
| YV | (L) |
10 mg/m3 | 8 h | acc. STERN, 1986 | |||
| Workp | D | L |
33 mg/m3 | MAK | DFG, 1989 | ||
| Workp | DDR | (L) |
55 mg/m3 | Long-time value | acc. HORN, 1989 | ||
| Workp | DDR | (L) |
110 mg/m3 | Short-time value | acc. HORN, 1989 | ||
| Workp | SU | (L) |
20 mg/m3 | acc. SORBE, 1989 | |||
| Workp | USA | (L) |
55 mg/m3 | TWA | ACGIH, 1986 | ||
| Workp | USA | (L) |
440 mg/m3 | STEL | ACGIH, 1986 | ||
| Workp | D | L |
5 %7) | BAT | Whole blood, end of shift | DFG, 1989 |
Notes:
1) Designated protection areas
2) 1/2 hour mean value (may be exceeded once per month at most)
3) Annual arithmetic mean for human health
4) 98% value of 1/2 hour mean values in one year
5) Specially designated protection areas
6) Areas other than those designated/specially designated as protection areas
7) CO haemoglobin
Comparison/reference values
| Medium/origin | Country | Value | Source |
| Air: | |||
| Rural areas | DDR | 0.01-0.9 mg/m3 | acc. HORN, 1989 |
| Atmosphere up to altitude of 10 km | 0.15 mg/m3 | acc. HORN, 1989 | |
| Urban areas | DDR | 10-60 mg/m3 (daily average) | acc. HORN, 1989 |
| Berlin, daily mean value | D | 15 mg/m3 | acc. UBA, 1977 |
| Cologne, daily mean value | D | 12 mg/m3 | acc. UBA, 1977 |
| Tunnels, garages | DDR | 115-570 mg/m3 | acc. HORN, 1989 |
| Gasworks, mines | DDR | < 660 mg/m3 | acc. HORN, 1989 |
Assessment/comments
Carbon monoxide is released into the environment by combustion processes particularly in road traffic. In view of the fact that inhaled carbon monoxide does considerable harm to humans and animals, the emissions must be regulated by filters and catalysts. In addition to its toxic effect, carbon monoxide is probably partly responsible for changes in the world climate (higher atmospheric temperatures) due to its rapid oxidation to form carbon dioxide.