- In the metallurgy industry, ethylene quickly becomes the preferred choice over propane and acetylene for cutting torches.
- The gas is not toxic itself but is a fire hazard and can have health consequences after short- and long-term exposure.
- Safety managers must use best workplace practices, including ethylene detection and checking, to avoid health and fire risks from emissions.
Ethylene gas use is increasing due to its wide range of industrial applications. However, the gas is not without risks. It can be a health and explosion hazard and must be used carefully. Find out its properties, safe limits, and the best practices necessary for its use.
Ethylene Use for Metallurgy
Ethylene, also called ethene, is a petrochemically derived monomer. It is used in many industries and is sometimes called the “World’s most important chemical.” Its importance can be judged by its use as an indicator of growth in the manufacturing sector.
Some industrial ethylene applications are in the petrochemical, LNG liquefaction, chemical, agricultural, automotive, medical, and metallurgical sectors.
In the metallurgical sector, ethylene is mainly used as an oxy-fuel gas for metal heating, welding, and cutting. It has been replacing acetylene and propane cutting torches since ethylene is less polluting and requires less energy and oxygen.
However, ethylene must also be used carefully due to its combustive and explosive nature and health and environmental risks, see Figure 1.
Ethylene is stored in liquid form by applying cryogenic temperatures and high pressure to the gas. Ethylene is liquified to make it easy to transport and store the gas. During use, the liquid ethylene is warmed to 0℃ to its gaseous state; then, oxygen is let in through an inlet, and the gas mixture is transported through a pipeline. Valves and flame temperature controls make the ethylene use process more safe.
Figure 1: Ethylene properties. (Image credits: https://gestis.dguv.de/data?name=012710&lang=en)
Ethylene is a hydrocarbon with the chemical formula C2H4.
At room temperature (around 20°C or 68°F), ethylene exists as a colorless gas. It has a sweet odor, but human detection capacity varies greatly. At very low temperatures, ethylene can be found in a liquid state.
The chemical properties of ethylene are as follows:
- Ethylene is a highly flammable gas.
- It forms explosive mixtures with air.
- It is only slightly soluble in water.
- There is a danger of suffocation at high concentrations due to oxygen displacement.
Due to its highly flammable nature and tendency to form explosive mixtures with air, implementing effective ethylene detection measures is crucial in environments where ethylene is present.
Hazardous Substance Classification
Ethylene is listed as a hazardous substance by various regulatory bodies, including ACGIH (American Conference of Governmental Industrial Hygienists), DOT (Department of Transportation), DEP (Department of Environmental Protection), NFPA (National Fire Protection Association), and EPA (Environmental Protection Agency).
Ethylene is a fire hazard due to its flammability and reactivity because,
- Ethylene is easily ignited and forms explosive mixtures with air.
- In the presence of a flame, it can flash back to the source of the leak.
- Prolonged exposure to fire or heat can cause containers to rupture violently, leading to the potential for explosions.
Understanding its flammability, reactivity, and potential health hazards is essential for working with or around this chemical.
One of the leading health risks is that exposure to ethylene is dangerous because it can replace oxygen and lead to suffocation. Besides this, acute and chronic health hazards can result from exposure to ethylene.
Acute Health Effects
Acute or short-term exposure to ethylene can lead to the following health effects immediately or shortly afterward:
- Skin Contact: Liquid ethylene can cause frostbite upon skin contact.
- General Exposure: Exposure to ethylene can lead to immediate symptoms such as headache, dizziness, fatigue, lightheadedness, confusion, and unconsciousness.
Chronic Health Effects
Repeated and long-term exposure to ethylene results in health effects that occur some time after and can last for months or years:
- Cancer Hazard: The information available suggests that ethylene has not been tested for its ability to cause animal cancer.
- Reproductive Hazard: Ethylene has not been tested for its potential effects on reproduction.
- Other Long-Term Effects: No specific information is provided regarding other chronic health effects.
Environmental Health Impact
Ethylene emissions can also pose environmental health hazards in two ways.
- Ozone Generation: Uncontrolled emissions of ethylene from industrial sources can lead to rapid ozone generation at the ground level.
- Ethylene Oxide Formation: Exogenous ethylene metabolically transforms into ethylene oxide in the human body. Ethylene oxide is noted as a mutagenic and carcinogenic substance. Due to these indirect effects, ethylene can be very harmful.
Workplace Exposure Limits
It’s essential to control and monitor ethylene emissions due to their potential impact on human health and the environment. Additionally, controlling industrial emissions of ethylene is crucial for preventing adverse health effects.
Occupational Exposure Limits:
The Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety & Health (NIOSH) have not established exposure limits for ethylene.
However, the ACGIH Threshold Limit Values (TLVs) for an 8-hour Time-weighted average (TWA) for a short-term exposure limit (STEL) ceiling is 200 parts per million (ppm). Though not legally enforceable, it provides valuable guidelines on safe limits for ethylene gas.
Oxygen Depletion: Large amounts of ethylene can reduce the available oxygen in the air. Regular testing of oxygen content is recommended to ensure it remains at least 19% by volume. Oxygen levels below this threshold can be hazardous to health.
Odor Threshold: The odor threshold for ethylene is 270ppm. The odor threshold is the concentration at which a substance can be detected by smell. However, reliance on odor alone may not warn of potentially hazardous exposures, as individual sensitivity to odors can vary.
Even though specific exposure limits have not been established for ethylene, it’s essential to exercise caution and adhere to safe work practices.
Reducing Ethylene Risks at Workplace
Workplace safety measures should be in place to minimize potential risks associated with ethylene exposure.
The guidelines to ensure the safety of individuals working with ethylene should include, but are not limited to, the following measures. It’s advisable to consult official occupational health and safety guidelines and regulations for the most up-to-date and detailed information and recommendations.
Training and Knowledge: Individuals should receive proper training on handling and storage before working with ethylene.
Ventilation: Enclose operations where possible. Use local exhaust ventilation at the site of chemical release to minimize exposure.
Engineering Controls: Ensure that engineering controls effectively prevent exposure to ethylene.
Monitoring: Use permanently installed and portable ethylene detection to monitor for dangerous releases of ethylene gas.
Respirators: If local exhaust ventilation or enclosure is impossible, individuals should wear respirators. Only use MSHA/NIOSH-approved self-contained breathing apparatus with a full facepiece operated in positive pressure mode in oxygen-deficient environments.
Protective Clothing: Wear protective work clothing to minimize skin contact.
Emergency Response: In skin contact, immediately submerge the affected body part in warm water. Wash thoroughly after exposure to ethylene.
Hazard Communication: Post hazard and warning information in the work area. Communicate information on ethylene’s health and safety hazards as part of ongoing education and training efforts.
These guidelines are crucial for maintaining a safe working environment when dealing with hazardous substances like ethylene.
Sensors for Ethylene Emission Detection
Fixed permanent ethylene detection is necessary to track ethylene. In addition, portable sensors for real-time reading in case of leaks will ensure that workers entering accident zones can measure ethylene levels to stay safe. Since STEL ethylene emissions must be below 200 ppm, precise instruments are needed. Interscan‘s GasD 8000 Series Portable Gas Analyzers include five options, of which three are suitable for ethylene as they have a measuring range of 0-200ppm, 0-500ppm, and 0-2000ppm, with a resolution of 0.1ppm, 0.1ppm, and 1ppm.
Workers must be aware of potential risks and follow safety protocols to prevent accidents and ensure their well-being.
Science Writer, CID Bio-Science
Ph.D. Ecology and Environmental Science, B.Sc Agriculture
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