Carbon Monoxide

Classification

Flammable gas, Category 1; Gas under pressure; Acute toxicity (inhalation), Category 3; Reproductive toxicity, Category 1A; Specific target organ toxicity, repeated exposure, Category 1

Hazard statements

• H220 Extremely flammable gas.
• H280 Contains gas under pressure; may explode if heated.
• H331 Toxic if inhaled.
• H360D May damage the unborn child.
• H372 Causes damage to organs through prolonged or repeated exposure.

Key precautionary statements

• P203 Obtain, read and follow all safety instructions before use.
• P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
• P260 Do not breathe gas.
• P271 Use only outdoors or in a well-ventilated area.
• P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
• P377 Leaking gas fire: Do not extinguish, unless leak can be stopped safely.
• P381 In case of leakage, eliminate all ignition sources.
• P410+P403 Protect from sunlight. Store in a well-ventilated place.

The federal OSHA PEL is 50 ppm TWA with no ceiling. NIOSH recommends 35 ppm TWA with a 200 ppm ceiling, and the ACGIH TLV is 25 ppm TWA. Cal/OSHA is stricter than federal OSHA at 25 ppm TWA and a 200 ppm ceiling. ACGIH also sets a biological exposure index based on carboxyhemoglobin in blood. Carbon monoxide has no odor or color, so continuous gas detection is the only reliable warning. State OSHA plans may set different limits.

• Appearance: Colorless gas, shipped as a compressed or liquefied gas
• Odor: Odorless
• Molecular weight: 28.0
• Boiling point: -313°F (-192°C)
• Freezing point: -337°F (-205°C)
• Flash point: Not applicable (flammable gas)
• Autoignition temperature: 1125°F (607°C)
• Explosive limits: LEL 12.5%, UEL 74%
• Vapor pressure: Greater than 35 atm
• Relative gas density: 0.97 (about the same as air)
• Water solubility: 2%

Inhalation

Carbon monoxide binds to hemoglobin and blocks oxygen delivery to the body. Early signs are headache, nausea, dizziness, weakness and rapid breathing, followed by confusion, chest pain, fainting and death at high levels. You cannot see or smell it.

Skin

The gas does not harm the skin. Contact with the liquefied gas causes frostbite.

Eyes

The gas does not irritate the eyes. Contact with the liquefied gas causes frostbite.

Ingestion

Not a relevant route for a gas.

Target organs

Cardiovascular system, lungs, blood, central nervous system

Long-term effects

Classified as a reproductive toxicant that may damage the unborn child, and as causing organ damage through prolonged or repeated exposure.

Gloves

Chemical-resistant gloves selected using the manufacturer's permeation data. Use insulated gloves where contact with liquefied gas or cold equipment is possible.

Eyes and face

Safety glasses with side shields when handling cylinders. Add a face shield where liquefied gas could splash.

Respiratory

NIOSH lists no chemical cartridge respirators for carbon monoxide. It recommends supplied-air respirators up to 875 ppm; a full-facepiece gas mask with chin-style canister, self-contained breathing apparatus or full-facepiece supplied-air respirator up to 1200 ppm; and a pressure-demand self-contained breathing apparatus for emergencies or unknown concentrations.

Clothing

Flame-resistant, anti-static clothing where flammable concentrations could occur. Remove clothing promptly if it becomes wet with the liquefied gas.

Store cylinders upright and secured, with valve caps in place, in a cool, dry, well-ventilated, separate area away from sunlight, ignition sources and oxidizers. Keep cylinder temperature below 125°F (52°C).

Use only in well-ventilated areas with continuous carbon monoxide monitoring. Use spark-proof tools and explosion-proof equipment, and purge lines with inert gas before maintenance.

Keep away from

• Strong oxidizers
• Bromine trifluoride
• Chlorine trifluoride
• Lithium

• Evacuate the area and call emergency responders.
• Do not enter without a self-contained breathing apparatus and a gas detector.
• Eliminate all ignition sources and use spark-proof tools and explosion-proof equipment.
• Stop the leak if it can be done safely, and ventilate the area.
• Follow ERG Guide 119.

Suitable extinguishing media

• Do not put out a leaking gas fire unless the leak can be stopped safely
• Water spray to cool containers
• Media suited to the surrounding fire

Special hazards

Carbon monoxide is extremely flammable. Cylinders exposed to fire can burst. Approach only with positive-pressure self-contained breathing apparatus, because the gas is toxic even when not burning.

• OSHA Hazard Communication (29 CFR 1910.1200): Hazardous chemical. Labels and safety data sheets are required.
• OSHA Air Contaminants (29 CFR 1910.1000, Table Z-1): PEL 50 ppm (55 mg/m³) TWA.
• EPA: Not listed as a CERCLA hazardous substance (40 CFR 302.4), an EPCRA extremely hazardous substance (40 CFR 355), or a Clean Air Act 112(r) regulated substance (40 CFR 68.130).
• DOT (49 CFR 172.101): UN1016, Carbon monoxide, compressed, Division 2.3 with subsidiary hazard 2.1; poison inhalation hazard.

• NIOSH Pocket Guide: Carbon monoxide
• PubChem: Carbon monoxide GHS classification
• OSHA Annotated PELs, Table Z-1
• Airgas SDS: Carbon Monoxide
• eCFR: CAA 112(r) regulated substances, 40 CFR 68.130