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Chemical Identifiers | Hazards | Response Recommendations | Physical Properties | Regulatory Information | Alternate Chemical Names

Chemical Identifiers

The Chemical Identifier fields include common identification numbers, the NFPA diamond, U.S. Department of Transportation hazard labels, and a general description of the chemical. The information in CAMEO Chemicals comes from a variety of data sources..
CAS Number UN/NA Number DOT Hazard Label USCG CHRIS Code
  • 7791-21-1
none data unavailable none
NFPA 704
Diamond Hazard Value Description
3 3
Blue Health 3 Can cause serious or permanent injury.
Red Flammability 4 Burns readily. Rapidly or completely vaporizes at atmospheric pressure and normal ambient temperature.
Yellow Instability 3 Capable of detonation or explosive decomposition or explosive reaction but requires a strong initiating source or must be heated under confinement before initiation.
White Special
(NFPA, 2010)
NIOSH Pocket Guide International Chem Safety Card
none none
General Description
Red-yellow gas. Very reactive and unstable. Unusually stored as hydrate in frozen form. Used as a wood bleach, biocide and swimming pool treatment.


The Hazard fields include special hazard alerts, air and water reactions, fire hazards, health hazards, a reactivity profile, and details about reactive groups assignments and potentially incompatible absorbents. The information in CAMEO Chemicals comes from a variety of data sources.
Reactivity Alerts
Air & Water Reactions
Decomposes in water forming chlorine and oxygen gases.
Fire Hazard
No information available.
Health Hazard
No information available.
Reactivity Profile
Explodes when heated or by reaction with organic materials, including: carbon, carbon disulfide, ethers, hydrocarbons, dicyanogen, any readily oxidizable materials (ammonia, potassium, arsenic, antimony, sulfur, mercury sulfide, calcium phosphide, phosphine, phosphorus, hydrogen sulfide, antimony sulfide, barium sulfide, mercury sulfide, and tin sulfide). Dissolves in alkalis, forming a mixture of chlorite and chlorate. Concentration of gas should be limited to less than 10% to reduce explosion hazard. Alcohols are oxidized explosively.
Belongs to the Following Reactive Group(s)
Potentially Incompatible Absorbents

Use caution: Liquids with this reactive group classification have been known to react with the absorbents listed below. More info about absorbents, including situations to watch out for...

Response Recommendations

The Response Recommendation fields include isolation and evacuation distances, as well as recommendations for firefighting, non-fire response, protective clothing, and first aid. The information in CAMEO Chemicals comes from a variety of data sources.
Isolation and Evacuation
No information available.
No information available.
Non-Fire Response
No information available.
Protective Clothing
No information available.
DuPont Tychem® Suit Fabrics
No information available.
First Aid
No information available.

Physical Properties

The Physical Property fields include properties such as vapor pressure and boiling point, as well as explosive limits and toxic exposure thresholds. The information in CAMEO Chemicals comes from a variety of data sources.
Chemical Formula:
  • Cl2O
Flash Point: data unavailable
Lower Explosive Limit (LEL): data unavailable
Upper Explosive Limit (UEL): data unavailable
Autoignition Temperature: data unavailable
Melting Point: data unavailable
Vapor Pressure: data unavailable
Vapor Density (Relative to Air): data unavailable
Specific Gravity: data unavailable
Boiling Point: data unavailable
Molecular Weight: data unavailable
Water Solubility: data unavailable
Ionization Potential: data unavailable
IDLH: data unavailable

AEGLs (Acute Exposure Guideline Levels)

No AEGL information available.

ERPGs (Emergency Response Planning Guidelines)

No ERPG information available.

PACs (Protective Action Criteria)

No PAC information available.

Regulatory Information

The Regulatory Information fields include information from the U.S. Environmental Protection Agency's Title III Consolidated List of Lists and the U.S. Department of Homeland Security's Chemical Facility Anti-Terrorism Standards (see more about these data sources).

EPA Consolidated List of Lists

Regulatory Name CAS Number/
313 Category Code
CAA 112(r)
Chlorine monoxide 7791-21-1 10000 pounds
Chlorine oxide 7791-21-1 10000 pounds

(EPA List of Lists, 2015)

DHS Chemical Facility Anti-Terrorism Standards (CFATS)

Chemical of Interest CAS Number Min Conc STQ Security
Min Conc STQ Security
Min Conc STQ Security
Chlorine monoxide; [Chlorine oxide] 7791-21-1 1.00 % 10000 pounds flammable

(DHS, 2007)

Alternate Chemical Names

This section provides a listing of alternate names for this chemical, including trade names and synonyms.