Todd Dunning
Todd DunningMAUnited States
Optical Materials for Laser Systems
Published
Dec 24, 2025

Carbon Monoxide (CO)

Chemical Properties

Chemical Identity

CAS Number
630-08-0
Formula
CO
Molecular Weight
28.01 g/mol

Exposure Limits Comparison

OSHA PEL
50 ppm
NIOSH REL
35 ppm
ACGIH TLV
25 ppm

Health Effects

Asphyxiation
Yes
Cardiovascular Effects
Yes
Headache
Yes
Dizziness
Yes
Fatal At High Dose
Yes

Carbon Monoxide (CO) safety information

Comprehensive safety and handling requirements

Detection Monitoring
Sensor Types
  • Electrochemical (most common)
  • Infrared (NDIR)
  • Semiconductor
  • Biomimetic gel (color change)
Detection Range0-300 ppm typical, 0-1000 ppm extended, 0-2000 ppm for rescue
Alarm Setpoints
Low35 ppm (NIOSH REL)
High200 ppm (NIOSH Ceiling)
Evacuate1200 ppm (NIOSH IDLH)
Colorimetric Tubes
  • Dräger CH25701
  • Gastec 1LC/1LB
  • Kitagawa 106SD
Analytical Methods
MethodTechniqueDetection Limit
NIOSH 6604GC-FID or electrochemical sensor0.03 ppm
OSHA ID-209GC-TCD (thermal conductivity)2 ppm
Odor ThresholdNO ODOR - Cannot be detected by smell. MUST use electronic monitors. Odorless nature makes CO extremely dangerous.
Environmental Impact
Aquatic ToxicityLow direct toxicity to aquatic life. LC50 (fish): >100 mg/L. Rapidly escapes to atmosphere from water.
BiodegradabilityNot biodegradable in conventional sense. Oxidizes to CO2 in atmosphere.
BioaccumulationNo bioaccumulation potential. Does not persist in environment.
Soil MobilityNot applicable - gas escapes to atmosphere immediately.
Atmospheric FateOxidizes to CO2 via hydroxyl radical reaction. Atmospheric lifetime: 1-2 months. Contributes to tropospheric ozone formation.
Ozone Depletionfalse
Global Warming PotentialIndirect effect via methane oxidation, but negligible GWP itself
Reportable Releases
WaterNot reportable (low aquatic persistence)
AirState-dependent. Many states require reporting large releases (e.g., >100 lbs/hr in some jurisdictions)
Ppe Requirements
RespiratoryNIOSH-approved full-face pressure-demand SCBA or supplied-air respirator with escape bottle for IDLH conditions. Continuous flow supplied-air for <1200 ppm.
Eye ProtectionSafety glasses. Face shield if handling compressed gas cylinders.
Skin ProtectionProtective gloves not normally required for gas (required for compressed gas cylinders). Thermal protection if handling cryogenic liquid.
Reactivity
StabilityStable under normal conditions.
PolymerizationWill not occur.
Incompatible Materials
  • Strong oxidizers (oxygen, halogens, fluorine, chlorine)
  • Silver oxide
  • Iron oxide
  • Bromine trifluoride
  • Nickel carbonyl (forms at high temperature)
Hazardous Decomposition
  • Carbon dioxide
  • Oxygen (incomplete combustion may regenerate CO)
Conditions To Avoid
  • Heat
  • Open flames
  • Sparks
  • Oxidizers
  • High temperatures
  • Confined spaces without ventilation
Reactivity HazardReacts violently with strong oxidizers. May form explosive mixtures with air (12.5-74%). Reacts with heated iron to form toxic iron carbonyl.
Regulatory Classification
Un NumberUN1016
Dot Hazard Class2.3 (Poisonous gas), 2.1 (Flammable gas)
Dot LabelPoison Gas, Flammable Gas
Nfpa Codes
Health3
Flammability4
Reactivity0
Epa Hazard Categories
  • Acute toxicity (inhalation)
  • Flammable gases
  • Gases under pressure
  • Reproductive toxicity
  • Specific target organ toxicity (single exposure)
Sara Title Iiifalse
Cercla RqNot listed (gas, difficult to quantify releases)
Rcra CodeNot listed as hazardous waste
Storage Requirements
Temperature RangeStore compressed gas cylinders below 52°C (125°F)
VentilationOutdoor storage preferred. If indoors: continuous mechanical ventilation, gas detection system with alarms
Incompatibilities
  • Strong oxidizers
  • Oxygen
  • Air (explosive mixtures)
  • Chlorine
  • Fluorine
  • Nitrous oxide
Container MaterialDOT-approved compressed gas cylinders (steel, aluminum). Do not transfer to unauthorized containers.
SegregationSeparate from oxygen cylinders by 20 feet or 5-foot non-combustible barrier. Store in dedicated gas cylinder storage.
Quantity LimitsPer 29 CFR 1910.253: Maximum 300 cubic feet indoors, unlimited outdoors with proper segregation
Special RequirementsSecure cylinders to prevent falling. Store upright. Cap cylinders when not in use. Post "CARBON MONOXIDE - POISON GAS" signs. Implement gas detection systems.

Produced From Contaminants

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Exposure Limits

Regulatory exposure thresholds and safe concentration levels

Osha Pel Ppm
50
Osha Pel Mg M3
55
Niosh Rel Ppm
35
Niosh Rel Mg M3
40
Acgih Tlv Ppm
25
Acgih Tlv Mg M3
29
Workplace Exposure
Osha Pel
twa_8hr: 50 ppm
stel_15min: null
ceiling: null
Niosh Rel
twa_8hr: 35 ppm
stel_15min: null
ceiling: 200 ppm (never to exceed)
idlh: 1200 ppm
Acgih Tlv
twa_8hr: 25 ppm
stel_15min: null
ceiling: null
Biological Exposure Indices
0: [object Object]

Physical Properties

Physical characteristics and state information

Boiling Point
-191.5°C (-312.7°F)
Melting Point
-205.1°C (-337.2°F)
Vapor Pressure
>760 mmHg @ 20°C (gas at normal temperature)
Vapor Density
0.968 (Air=1)
Specific Gravity
0.791 @ -191.5°C (liquid)
Flash Point
Not applicable (gas)
Autoignition Temp
609°C (1128°F)
Explosive Limits
LEL: 12.5%, UEL: 74%
Appearance
Colorless gas
Odor
Odorless - Cannot be detected by smell (DANGEROUS!)

Reactivity

Chemical reactivity and compatibility with other substances

Stability
Stable under normal conditions.
Polymerization
Will not occur.
Incompatible Materials
  • Strong oxidizers (oxygen, halogens, fluorine, chlorine)
  • Silver oxide
  • Iron oxide
  • Bromine trifluoride
  • Nickel carbonyl (forms at high temperature)
Hazardous Decomposition
  • Carbon dioxide
  • Oxygen (incomplete combustion may regenerate CO)
Conditions To Avoid
  • Heat
  • Open flames
  • Sparks
  • Oxidizers
  • High temperatures
  • Confined spaces without ventilation
Reactivity Hazard
Reacts violently with strong oxidizers. May form explosive mixtures with air (12.5-74%). Reacts with heated iron to form toxic iron carbonyl.

Synonyms & Identifiers

Alternative names and chemical identifiers (CAS numbers)

Synonyms
  • Carbon oxide
  • Carbonic oxide
  • Flue gas
  • Exhaust gas
  • CO
Common Trade Names
    Other Identifiers
    Rtecs Number
    FG3500000
    Ec Number
    211-128-3
    Pubchem Cid
    281