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Subchapter 7. General Industry Safety Orders
Group 16. Control of Hazardous Substances
Article 110. Regulated Carcinogens
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§5220. Ethylene Oxide, Appendix B

Substance Technical Guidelines

for Ethylene Oxide


(A) Substance identification

(1) Synonyms: dihydrooxirene, dimethylene oxide, EO, 1, 2-epoxyethane, EtO, ETO, oxacyclopropane, oxane, oxidoethane, alpha/beta-oxidoethane, oxiran, oxirane

(2) Formula:

(3) Molecular weight: 44.06

(B) Physical data:

(1) Boiling point (760 mm Hg): 10.7° C (51.3° F)

(2) Specific gravity (water = 1): 0.87 (at 20° C or 68° F)

(3) Vapor density (air = 1): 1.49

(4) Vapor pressure (at 20° C): 1,095 mm Hg

(5) Solubility in water: complete

(6) Appearance and odor: colorless liquid; gas at temperatures above 10.7°F (51.3°C) with an ether-like odor detectable above 700 ppm


(A) Fire:

(1) Flash point: less than 0° F (open cup);

(2) Stability: decomposes violently at temperatures above 800° F;

(3) Flammable limits in air, percent by volume: Lower: 3, Upper: 100;

(4) Extinguishing media: Carbon dioxide for small fires, polymer or alcohol foams for large fires;

(5) Special fire fighting procedures: Dilution of ethylene oxide with 23 volumes of water renders it non-flammable;

(6) Unusual fire and explosion hazards: Vapors of EtO will burn without the presence of air or other oxidizers. EtO vapors are heavier than air and may travel along the ground and be ignited by open flames or sparks at locations remote from the site at which EtO is being used.

(7) For purposes of compliance with the requirements of Articles 141 through 148 of the General Industry Safety Orders, EtO is classified as a flammable gas. For example, 7,500 ppm, approximately one-fourth of the lower flammable limit, would be considered to pose a potential fire and explosion hazard.

(8) For purposes of compliance with regulations for fire protection, EtO is classified as a Class B fire hazard.

(9) For purposes of compliance with the Electrical Safety Orders (California Administrative Code, Title 8, Subchapters 5 and 6), locations classified as hazardous due to the presence of EtO shall be Class I.

(B) Reactivity:

(1) Conditions contributing to instability: EtO will polymerize violently if contaminated with aqueous alkalies, amines, mineral acids, metal chlorides, or metal oxides. Violent decomposition will also occur at temperatures above 800°F;

(2) Incompatibilities: Alkalies and acids;

(3) Hazardous decomposition products: Carbon monoxide and carbon dioxide.


(A) If EtO is spilled or leaked, the following steps should be taken:

(1) Remove all ignition sources.

(2) The area should be evacuated at once and re-entered only after the area has been thoroughly ventilated and washed down with water.

(B) Persons not wearing appropriate protective equipment must be restricted from areas of spills or leaks until cleanup has been completed.

(C) Waste disposal methods: Waste material shall be disposed of in a manner that is not hazardous to employees or to the general population. In selecting the method of waste disposal, applicable local, State, and Federal regulations should be consulted.


(A) Exposure above the Permissible Exposure Limit:

(1) Measurements taken for the purpose of determining employee exposure under this section are best taken with consecutive samples covering the full shift. Air samples must be taken in the employee's breathing zone (air that would most nearly represent that inhaled by the employee).

(2) The sampling and analysis under this section may be performed by collection of the EtO vapor on charcoal adsorption tubes or other composition adsorption tubes, with subsequent chemical analysis. Sampling and analysis may also be performed by instruments such as a real-time continuous monitoring systems, portable direct reading instruments, or passive dosimeters provided measurements taken using these methods accurately evaluate the concentration of EtO in employees' breathing zones.

Appendix D describes the validated method of sampling and analysis which has been tested by Federal OSHA for use with EtO. The employer has the obligation of selecting a monitoring method which meets the accuracy and precision requirements of the standard under his or her unique field conditions. The standard requires that the method of monitoring must be accurate, to a 95 percent confidence level, to plus or minus 25 percent for concentrations of EtO at 1 ppm and to plus or minus 35 percent for concentrations at 0.5 ppm.

(B) Since many of the employer's duties under the regulation depend upon the results of employee exposure measurements, employers must assure that the evaluation of employee exposures is performed by a technically qualified person.


Employees shall be provided with and be required to wear appropriate protective clothing wherever there is significant potential for skin contact with liquid EtO or EtO-containing solutions. Protective clothing shall include impermeable coveralls or similar full-body work clothing, gloves, and head coverings, as appropriate to protect areas of the body which may come in contact with liquid EtO or EtO-containing solutions.

Employers must ascertain that the protective garments are impermeable to EtO. Permeable clothing, including items made of rubber, and leather shoes should not be allowed to become contaminated with liquid EtO or EtO-containing solutions. If permeable clothing does become contaminated, it should be immediately removed while the employee is under an emergency deluge shower. If leather footwear or other leather garments become wet from EtO they should be discarded and not be worn again because leather absorbs EtO and holds it against the skin.

Any protective clothing that has been damaged or is otherwise found to be defective should be repaired or replaced. Clean protective clothing should be provided to the employee as necessary to assure employee protection. Whenever impermeable clothing becomes wet with liquid EtO or EtO-containing solutions, it should be washed down with water before being removed by the employee. Employees are also required to wear splash-proof safety goggles where there is any possibility of EtO contacting the eyes.


(A) Store EtO in tightly closed containers in a cool, well-ventilated area and take all necessary precautions to avoid any explosion hazard.

(B) Non-sparking tools must be used to open and close metal containers. These containers must be effectively grounded and bonded.

(C) Do not incinerate EtO cartridges, tanks or other containers.

(D) Employers shall advise employees of all areas and operations where exposure to EtO could occur.


Common operations in which exposure to EtO is likely to occur include the following: Manufacture of EtO, surfactants, ethanolamines, glycol ethers, and specialty chemicals, and use as a sterilant and fumigant in the hospital, health product and spice industries.

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