The following information has been extracted from our CHEMINFO database, which also contains hazard control and regulatory information. [More about...] [Sample Record]

Access the complete CHEMINFO database by contacting CCOHS Client Services.


CHEMINFO Record Number: 223
CCOHS Chemical Name: Cyclohexyl isocyanate

Isocyanic acid, cyclohexyl ester

Chemical Name French: Isocyanate de cyclohexyle
Chemical Name Spanish: Isocianato de ciclohexilo
CAS Registry Number: 3173-53-3
UN/NA Number(s): 2488
RTECS Number(s): NQ8650000
EU EINECS/ELINCS Number: 221-639-3
Chemical Family: Isocyanic acid ester / isocyanate / aliphatic isocyanate / monoisocyanate / aliphatic monoisocyanate
Molecular Formula: C7-H11-N-O
Structural Formula: C6H11-N=C=O (C6H11=cyclohexane ring)


Appearance and Odour:
Colourless to pale yellow liquid; lachrymator (vapour irritates the eyes and causes tears).(7)

Odour Threshold:
No information available

Warning Properties:
Information not available for evaluation

Uses and Occurrences:
Monoisocyanates are used as chemical intermediates in the production of drugs, pesticides, amines, ureas and other carbamoyl compounds.(1)


Colourless to pale yellow liquid. Lachrymator. COMBUSTIBLE LIQUID AND VAPOUR. Can decompose at high temperatures forming toxic gases, such as nitrogen oxides and hydrogen cyanide. Closed containers may develop pressure and rupture on prolonged exposure to heat. Reacts violently with water. May polymerize if heated or in contact with water. VERY TOXIC. May be fatal if inhaled or swallowed. Vapour may be extremely irritating to the eyes and respiratory tract. May cause lung injury--effects may be delayed. Liquid causes skin and eye irritation.


Effects of Short-Term (Acute) Exposure

Cyclohexyl isocyanate (CHI) is a strong irritant and initial injury is probably confined to areas of direct contact such as the nose, mouth and respiratory tract. Very serious and persistent respiratory system and lung damage may occur which can result in death.
Typical symptoms include breathlessness, dry cough, throat irritation or choking, chest pain/tightness, difficulty in breathing and possibly coughing up blood, as well as lethargy, loss of appetite, convulsions and coma.(1) Symptoms may appear immediately or may be delayed several hours after exposure, depending upon the concentration, and may continue for 3 to 7 days or longer. Permanent lung damage may result.
Inhalation of very high levels might cause chemical bronchitis with asthma- like wheezing and can be fatal due to severe respiratory tract and lung damage (pulmonary edema).
There are currently no reports of these effects in people working with CHI.

Skin Contact:
The liquid can cause moderate skin irritation, with swelling and redness. There is no human information but it caused moderate skin irritation in laboratory animals.(1) Like other isocyanates, CHI may cause skin sensitization, although there are no reports of this happening.

Eye Contact:
The liquid may cause severe eye injury. There are no human reports but it caused severe eye injury in laboratory animals.(1)
Exposure to the vapour can cause irritation with tearing. Exposure to very high concentrations can result in severe eye injury, including intense burning of the eyes, and corneal ulcerations. In most cases, these effects are expected to be temporary.

There have been no reports of people ingesting CHI and ingestion is unlikely to occur in the workplace. Ingestion would probably cause irritation of the mouth, throat and digestive tract.

Effects of Long-Term (Chronic) Exposure

Lungs/Respiratory System:
CHI is a severe respiratory irritant. Long-term, low- level exposure could result in severe, permanent respiratory impairment.

Exposure to isocyanates is likely to aggravate individuals with existing respiratory disease, such as chronic bronchitis, and emphysema.

Respiratory Sensitization:
Some, isocyanates are well known to cause respiratory sensitization. However, there are no reports of CHI or other monoisocyantes causing respiratory sensitization in humans or animals.
Isocyanate respiratory sensitization is usually caused by a very large exposure, or by multiple exposures. Although varying periods of exposure (1 day to years) may elapse before sensitization occurs, it develops more often during the first few months of exposure. Sensitized individuals react to very low levels of airborne isocyanates that have no effect on unsensitized people.(2)
Cross-sensitization between different isocyanates may occur.(3)

Skin Sensitization:
There have been no reports of CHI causing skin sensitization in humans. Some other isocyanates are skin sensitizers.


There is no human or animal information.

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has no listing for this chemical.

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
There is no human or animal information.

Reproductive Toxicity:
There is no human or animal information.

No human or animal in vivo studies are available. CHI was positive in a bacterial (Ames) test.(6)

Toxicologically Synergistic Materials:
Insufficient information

Potential for Accumulation:
Probably does not accumulate. Reacts with water and tissues to form cyclohexylamine.


Take proper precautions to ensure your own safety before attempting rescue (e.g. wear appropriate protective equipment, use the buddy system). Remove source of contamination or move victim to fresh air. If breathing is difficult, oxygen may be beneficial if administered by trained personnel, preferably on a doctor's advice. DO NOT allow victim to move about unnecessarily. Symptoms of pulmonary edema can be delayed up to 48 hours after exposure. Immediately transport victim to an emergency care facility.

Skin Contact:
Avoid direct contact. Wear chemical protective clothing, if necessary. Quickly and gently blot or brush away excess chemical. Wash gently and thoroughly with water and non-abrasive soap for 20 minutes or until chemical is removed. Under running water, remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Obtain medical attention immediately. Discard contaminated clothing, shoes and leather goods.

Eye Contact:
Avoid direct contact. Wear chemical protective gloves, if necessary. Quickly and gently blot or brush away excess chemical. Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for 20 minutes, or until the chemical is removed while holding the eyelid(s) open. Take care not to rinse contaminated water into non-affected eye. Obtain medical attention immediately.

NEVER give anything by mouth if victim is rapidly losing consciousness, or is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. Have victim drink 240 to 300 mL (8 to 10 oz.) of water to dilute material in stomach. Obtain medical attention immediately.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest). Consult a doctor and/or the nearest Poison Control Centre for all exposures except under minor instances of inhalation or skin contact. Some recommendations in the above sections may be considered medical acts in some jurisdictions. These recommendations should be reviewed with a doctor and appropriate delegation of authority obtained, as required.
All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.


Flash Point:
48 deg C (118.4 deg F) (11)

Lower Flammable (Explosive) Limit (LFL/LEL):
Not available

Upper Flammable (Explosive) Limit (UFL/UEL):
Information not available

Autoignition (Ignition) Temperature:
Information not available

Sensitivity to Mechanical Impact:
Insufficient information. Probably not sensitive, since it is a stable material.

Sensitivity to Static Charge:
Insufficient information.

Combustion and Thermal Decomposition Products:
Carbon monoxide, carbon dioxide, nitrogen oxides, hydrogen cyanide.(7)

Fire Hazard Summary:
Combustible liquid. Can form explosive mixtures with air at, or above 48 deg C. During a fire, irritating/toxic nitrogen oxides and hydrogen cyanide may be generated. Vapour may cause death if it penetrates the firefighter's normal protective gear. Reacts violently with water. Can accumulate in confined spaces, resulting in a toxicity hazard. Closed containers may rupture violently when heated.

Extinguishing Media:
Dry chemical powder, carbon dioxide, protein foam. Water spray or fog may be used for cooling. Water-based extinguishers and foams should not be used on CHI since the reaction is violent.

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or a protected location. Approach fire from upwind to avoid hazardous vapours and toxic decomposition products.
If possible, isolate materials not yet involved in the fire. Closed containers or tanks may explode in the heat of the fire. Move containers from fire area if this can be done without risk. Otherwise, keep fire- exposed tanks or containers cool by application of hose streams. Application of cooling streams should begin as soon as possible. If this is not possible, set up unmanned monitor nozzles and evacuate the area. Take care not to get water inside container.
CHI can react violently with water and water-based fire extinguishers. Water can be used as a spray or fog to absorb heat and protect exposed material of structures. If a leak or spill has not ignited, use water spray in large quantities to disperse the vapours and to protect personnel attempting to stop a leak. However, proper care must be taken because of the violent reaction between water and CHI.
After the fire has been extinguished, the area should not be considered safe until a thorough inspection for residual isocyanate has been carried out by properly protected personnel.
CHI and its decomposition products, such as hydrogen cyanide and nitrogen oxides, are extremely hazardous to health. Do not enter without specialized protective equipment suitable for the situation. Firefighter's normal protective clothing (Bunker Gear) will not provide adequate protection. A full-body encapsulating chemical resistant suit with positive pressure self- contained breathing apparatus (MSHA/NIOSH approved or equivalent) may be necessary.


NFPA - Comments:
NFPA has no listing for this chemical in Codes 49 or 325.


Molecular Weight: 125.17

Conversion Factor:
1 ppm = 5.12 mg/m3; 1 mg/m3 = 0.2 ppm at 25 deg C

Physical State: Liquid
Melting Point: Less than -80 deg C (-112 deg F) (8)
Boiling Point: 168-170 deg C (334-338 deg F) (7)
Relative Density (Specific Gravity): 0.96 at 20 deg C (water = 1) (8)
Solubility in Water: Probably insoluble. Reacts with water.
Solubility in Other Liquids: Not available
Coefficient of Oil/Water Distribution (Partition Coefficient): Not applicable (reacts with water)
pH Value: Not applicable (reacts with water)
Vapour Density: 4.3 (air = 1)
Vapour Pressure: 0.27 kPa (2.0 mm Hg) at 25 deg C (7)
Saturation Vapour Concentration: Approximately 2600 ppm (0.26%) at 25 deg C (calculated)
Evaporation Rate: Not available
Critical Temperature: Not available


Normally stable. It self-reacts at elevated temperatures to form trimers and polymers giving off carbon dioxide and heat.(8)

Hazardous Polymerization:
CHI may undergo uncontrolled exothermic trimerization and polymerization upon contact with incompatible materials, such as trialkyl phosphines, triphenylarsenic, potassium acetate and many metal compounds soluble in organic media, such as organotin compounds, or if heated.(8) The heat and products generated from this reaction can result in a pressure build-up in closed containers that is sometimes sufficient to rupture the container.

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.

WATER - Reacts vigorously or violently, forming carbon dioxide gas and dicyclohexylurea. The reaction may become progressively more vigorous at higher temperatures.(8) Closed containers can rupture explosively when contaminated with water.
STRONG OXIDIZING AGENTS - May react violently with the risk of fire and explosion.(7)
ALCOHOLS, ACIDS, BASES, AMINES - May react vigorously or violently with the risk of fire and explosion.(7)
CERTAIN CATALYSTS (e.g. triphenylarsenic oxide and tributyl tin oxide) - may cause a violent reaction.(8)

Hazardous Decomposition Products:
Cyclohexylamine (formed by reaction of CHI with water)

Conditions to Avoid:
Sparks, open flames, electrostatic discharge, heat, other ignition sources, moisture.

Corrosivity to Metals:
Information not available

Stability and Reactivity Comments:
Isocyanates are very reactive compounds and are especially highly reactive toward a large number of compounds with active hydrogens, particularly at high temperatures and in the presence of catalysts.(8) See references 8 for some of the reactions of isocyanates.


Standard animal toxicity values are not available.

Eye Irritation:

Cyclohexyl isocyanate (CHI) caused severe injury when it was applied to the eyes of laboratory animals (probably rabbits).(1)

Skin Irritation:

CHI caused moderate skin irritation in laboratory animals (probably rabbits).(1)


Selected Bibliography:
(1) Woolrich, P.F. Monoisocyanates, diisocyanates and polyisocyanates: engineering, medical control and toxicologic considerations. Technical bulletin 106. The Upjohn Company, 1973
(2) Karol, M.H. Respiratory effects of inhaled isocyanates. CRC Critical Reviews in Toxicology. Vol. 16, issue 4 (1986). p. 349-379
(3) Musk, A.W., et al. Isocyanates and respiratory disease: current status. American Journal of Industrial Medicine. Vol. 13, no. 3 (1988). p. 331-349
(4) RTECS record for isocyanic acid, cyclohexyl ester. Date of last update: 9410
(5) Dewair, M., et al. Inhibition of acetylcholinesterase from human erythrocytes by isocyanates. Journal of Occupational Medicine. Vol. 25, No. 4 (1983). p. 279-282
(6) Yamaguchi, T. Mutagenicity of isothiocyanates, isocyanates and thioureas on Salmonella typhimurium. Agricultural and Biological Chemistry. Vol. 44, no. 12 (1980). p. 3017-3018
(7) The Sigma-Aldrich library of chemical safety data. Edition II. Volume 1. Sigma-Aldrich Corporation, 1988. p. 974A
(8) Kirk-Othmer encyclopedia of chemical technology. 3rd. edition. Vol. 13. John Wiley and Sons, 1981. p. 789-818
(9) Key-Schwartz, R.J. Analytical problems encountered with NIOSH method 5521 for total isocyanates. AIHA Journal. Vol. 56 (1995). p. 474-479
(10) Streicher, R.P., et al. Investigation of the ability of MDHS method 25 to determine urethane-bound isocyanate groups. AIHA Journal. Vol. 56 (1995). p. 437- 442
(11) Dean, J.A. Lange's handbook of chemistry. 15th ed. McGraw-Hill, Inc., 1999. p. 1.159

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 1995-03-07

Revision Indicators:
Chronic exposure 1995-05-01
Fire fighting instructions 1995-05-01
Extinguishing media 1995-05-01
TLV-STEL 1995-11-01
TLV comments 1995-11-01
Respiratory guidelines 1995-11-01
EU class 1995-11-01
US transport 1998-03-01
Bibliography 1998-06-01
Resistance of materials 1998-06-01
TDG 2002-05-27

©2007 Canadian  Centre  for  Occupational  Health  &  Safety  E-mail:  Fax: (905) 572-2206  Phone: (905) 572-2981  
Mail:  250  Main  Street  East,  Hamilton  Ontario  L8N  1H6