Ethylene Oxide

WHAT IS ETHYLENE OXIDE ? 
Ethylene oxide is a colorless gas with a sweet odor. Ethylene Oxide exists as a colourless liquid below 10 degrees Celcius. It is an extremely flammable gas. The gas is slightly heavier than air and may spread long distances. Distant ignition and flashback are possible. The liquid can accumulate static charge by splashing or agitation. Ethylene oxide can decompose explosively. Cylinders and closed containers may rupture violently if heated. It is a compressed gas. It is also dangerously reactive. Ethylene oxide may polymerize or decompose violently when exposed to high temperatures or contaminants (e.g. acids and metals). 

Ethylene Oxide is also known as Dihydrooxirene, Dimethylene oxide, EO, EtO, 1,2-Epoxyethane, Epoxyethane, Ethene oxide, Oxacyclopropane, Oxane, Oxidoethane , Oxirane, Oxyde d'éthylène. 

WHERE IS ETHYLENE OXIDE USED?
Ethylene Oxide (EtO) is produced in large volumes and is primarily used as a chemical intermediate in the manufacture of several industrial chemicals including textiles, detergents, polyurethane foam, antifreeze, solvents, medicinal products, adhesives, and other related products. The most notable product involving the use of sizable quantities of Ethylene Oxide Ethylene Glycol. It is also used as a fumigant in certain agricultural products and as a sterilizing agent for food (spices), cosmetics, medical equipment as well as for the sterilization of surgical tool and plastic devices in hospitals that cannot be sterilized by steam..

Over the past 50 years, there have been many incidents in both EtO production plants and EtO consuming plants resulting in major plant damage, as well as fatalities. There have also been a significant number of EtO transportation incidents.

WHAT ARE THE HEALTH HAZARDS OF ETHYLENE OXIDE ? 
Ethylene Oxide possesses several physical and health hazards that merit special attention. EtO is both flammable and highly reactive. Acute exposures to EtO gas may result in respiratory irritation and lung injury, headache, nausea, vomiting, diarrhea, shortness of breath, and cyanosis. Chronic exposure has been associated with the occurrence of cancer, reproductive effects, mutagenic changes, neurotoxicity, and sensitization.

Ethylene Oxide is very toxic and may be fatal if inhaled. It is irritating to the respiratory tract and is a central nervous system depressant. This means that high concentrations may cause headache, nausea, dizziness, drowsiness, and in co-ordination. Solutions cause skin irritation and probably cause eye irritation. Ethylene oxide is a cancer hazard - It can cause cancer, based on human information. It is also a possible reproductive hazard (It may harm reproductive capability, based on animal information) and a mutagen (It may cause inheritable genetic damage). 

COMPOSITION AND PURITY OF ETHYLENE OXIDE: 
Ethylene Oxide (EtO) is a high purity chemical (99.7% or higher). Impurities may include acetaldehyde, acetic acid, acetylene, and inorganic and organic chlorides. It is also available as an non-flammable mixture with nitrogen or carbon dioxide. Historically, mixtures with dichlorodifluoromethane (Fluorocarbon 12) were available, but environmental concerns have led to the use of other flame retardant diluent gases. EtO is shipped as a liquid under its own vapour pressure of 50 kPa at 21.1 deg C in compressed gas cylinders, special containers, such as insulated steel drums, portable tanks or insulated single-unit tank cars.

WHAT ARE THE FIRE AND EXPLOSION DANGERS ASSOCIATED WITH ETHYLENE OXIDE? 
Ethylene Oxide is an extremely flammable gas (above 10 degrees C) or liquid (below 10 degrees C) that will readily ignite at room temperature. Liquid can accumulate static charge by splashing or agitation. Gas can be ignited by a static charge. Solutions containing greater than 4 wt% ethylene oxide (EO) are flammable. The gas is slightly heavier than air and can travel a considerable distance to a source of ignition and flash back to a leak or open container. 

Explosive decomposition may occur. The gas forms explosive mixtures with air over an extremely wide range. Although the gas itself has a high minimum ignition energy (approximately 1000 millijoules), air mixtures have an extremely low minimum ignition energy (0.06 millijoules) and easily ignite. Once ignited, pure liquid EtO will burn explosively at or below the surface and a propagating flame may be produced. 

The heat of a fire may cause spontaneous polymerization, which can cause containers to rupture violently. EtO can burn in sealed containers if ignited. Under fire conditions, an EtO pipeline may undergo internal decomposition. Explosions will occur if gas or vapours are ignited in a confined area. 

HOW CAN I WORK WITH ETHYLENE OXIDE SAFELY? 
EtO is a very toxic (cancer hazard, mutagen), compressed, extremely flammable gas. EtO is also dangerously reactive. Before handling, it is extremely important that engineering controls are operating and that protective equipment requirements and personal hygiene measures are being followed. Control access to designated handling area. Post appropriate warning signs. Only authorized personnel should have access to EtO. They should be properly trained regarding its hazards and its safe use. Maintenance and emergency personnel should be advised of potential hazards. 

Prevent release of gas into workplace air. Closed handling systems for processes involving EtO should be used. To reduce the fire/explosion hazard, consider the use of an inert gas in the container or storage vessel. If a closed handling system is not possible, use in smallest possible amounts in appropriate labelled, containment devices (e.g. fume hood). Containment devices should be made of smooth, unbreakable, compatible material. Maintain containment devices at appropriate air flow and negative pressure. Check regularly. 

Eliminate all ignition sources (e.g. sparks, open flames, hot surfaces). Keep away from heat. Post "NO SMOKING" signs. It is very important to keep areas where EtO is used clear of other materials which can burn (e.g. cardboard, sawdust). 

Immediately report leaks or ventilation failures. Unprotected persons should avoid all contact with EtO and contaminated equipment. If EtO is released, immediately put on a suitable respirator and leave the area until the severity of the release is determined. In case of leaks or spills, escape-type respiratory protective equipment should be available in the work area. EtO is extremely reactive. Prevent exposure to elevated temperatures and absolutely no contact with even trace amounts of incompatible materials. Do not use with incompatible materials such as oxidizing agents, acids, bases and alcohols. 

Use non-sparking ventilation systems, approved explosion-proof equipment and intrinsically safe electrical systems in areas of use. Consider the installation of leak and fire detection equipment along with a suitable, automatic fire suppression system. Keep aisles and exits free of obstruction. Do not use near welding operations, flames or hot surfaces. Do not perform any welding, cutting, soldering, drilling or other hot work on an empty vessel, container or piping until it has been thoroughly decontaminated. To prevent sparking, generously wet hard surfaces before they are chipped, ground, etc, in potentially hazardous areas. Do not heat compressed gas cylinders. Inspect cylinders for leaks before handling. During transfer operations, cylinders and vessels should be electrically grounded and bonded to prevent the build-up of a static charge. Leave cylinder cap on cylinder until cylinder is secured and ready for use. Always secure cylinders to a wall, rack or other solid structure in an upright position. Do not handle cylinders with oily hands. Regularly check cylinders for evidence of corrosion or leakage. Make sure cylinders are labelled clearly. Use the appropriate pressure regulator. Ensure equipment is compatible with cylinder pressure and contents. Follow supplier recommendations. 

Before connecting the cylinder for use, make sure that back feed from the system into the cylinder is prevented. Suck-back into cylinder may cause explosion. Prevent cylinder entry tube from being inserted in a liquid or gas without a vacuum-break or other protective device. 

Avoid damaging cylinders. Do not open cylinder if damaged. Never use excessive force when opening. Open cylinder valve slowly to prevent rapid decompression and damage to valve seat. Keep cylinder valves clean and free from contaminants. Make sure valves on gas cylinders are fully opened when gas is used. Open and shut valves at least once a day, while cylinder is in use, to avoid valve 'freezing'. Shut flow off at cylinder valve and not just at the regulator after use. Replace outlet caps or plugs and cylinder caps as soon as cylinder is disconnected from equipment. 

Keep empty cylinders under slightly positive pressure. Do not use cylinders as rollers or for any other purpose than to contain the gas as supplied. Move cylinders by hand truck or cart designed for that purpose. Do not drop cylinders or permit them to bang against each other. Do not lift cylinders by the cap or with a lifting magnet. 

Follow handling precautions on Material Safety Data Sheet. Have suitable emergency equipment for fires and leaks readily available. Practice good housekeeping. Maintain handling equipment. Comply with applicable regulations. 

WHAT CAN BE DONE TO CONTROL HAZARDOUS CONDITIONS? 
Engineering control methods to reduce hazardous exposures are preferred. Methods include mechanical ventilation (local exhaust), process or personnel enclosure, control of the process conditions and process modification (e.g. substitution of a less hazardous material). Administrative controls and personal protective equipment may also be required. 

Because of the high potential hazard associated with EtO, stringent control measures such as enclosure (closed handling systems) are recommended. A combined sterilization/aeration facility should be used wherever possible. To reduce the fire hazard, consider the use of an inert gas in the handling system. Use non-sparking, grounded ventilation system separate from other exhaust ventilation systems. Exhaust directly to the outside. Supply sufficient replacement air to make up for air removed by exhaust systems. Use approved explosion-proof equipment and intrinsically safe electrical systems in areas of use. Consider the installation of leak and fire detection equipment along with a suitable, automatic fire suppression system.