Health and safety risks of chlorine gas can occur during professional or personal use. Widely used in manufacturing and industrial applications, chlorine gas can become a severe hazard if accidental release, leaks, or transportation incidents occur. Knowing what chlorine is, as well as its health and safety risks is critical.
What is Chlorine?
CAS Number: 7782-50-5
Chemical Compound: Cl2
Other names: Molecular chlorine, dichlorine, chlorinated water, bertholite, Javelle water, and sodium hypochlorite
Molecular weight: 70.91
Specific gravity: 1.56 (LIQUID, -34.6°C)
Boiling point: -34.6°C
Melting point: -101°C
Vapour pressure: 4800 mmHg (at 20°C)
Chlorine is a naturally occurring chemical element, although due to its reactive nature, it is rarely found in its natural form. It is more commonly found bonded into compounds such as table salt (NaCl).
Chlorine can exist as a liquid or gas; however, under normal atmospheric conditions, liquid Cl would vaporise. Chlorine gas has a visible, yellow-green colour with a pungent, irritating odour. The gas is heavier than air and spreads rapidly.
While it is non-flammable, chlorine is highly reactive; forming toxic, explosive or acidic elements when combined with other materials or compounds.
How is Chlorine Used?
Chlorines ability to combine with other elements and compounds is commonly used in a wide range of applications from manufacturing (production of pesticides, rubber, solvents, and plastics), industrial (sewage, water treatment, paper and fabric bleaching), domestically (swimming pools, cleaners) and healthcare (pharmaceuticals).
To be stored and transported, it is pressurised and cooled to change into a liquid form. If liquid chlorine is released, it quickly turns into a gas.
Safety Hazards of Chlorine
Chlorine gas hazards can occur during manufacture, use and transportation. An in-depth emergency response plan and ongoing training are necessary to mitigate the risk of a crisis.
Though most facilities are designed to minimise the risk of a chlorine release, accidental releases and leaks are possible. Monitoring equipment should be in place to detect signs of gas leaks and prompt appropriate action.
Chlorine gas is a strong irritant to the respiratory system, eyes, skin, and mucous membranes. In high concentrations, chlorine can take the form of poisonous gas.
Immediate signs and symptoms of chlorine exposure can range from blurred vision, skin irritation (blistering, redness, and frostbite), coughing, difficulty breathing, or nausea and vomiting. After some time, fluid in the lungs can develop.
The toxicity of chlorine is due to its corrosive effects. When chlorine comes in contact with moist tissue such as skin, eyes, throat and lungs, it forms an acid which causes damage to the area. Also, chlorine reacts with water to form hydrochloric acid and hypochlorous acid, both of which are very corrosive.
Chlorine Gas Release: Plume Hazards
Chlorine use is widespread, from the manufacturing of medication to industrial bleaching. The frequency and commonality of chlorine increase the risk of accidental release.
In 2018, the American Association of Poison Control Centres reported over 3,000 chlorine gas exposures (excluding household acid is mixed with hypochlorite and swimming pools). Petrochemical companies working with chlorine gas must be aware of the risk of an accidental release and chlorine toxicity.
How long for chlorine gas to dissipate? The duration and behaviour of a chemical plume are dependent on many factors. These include the product released, its chemical and physical properties, the volume released, ambient temperature, time of day, relative humidity, wind direction and speed, terrain, natural and urban barriers and environmental sorption factors such as dense and sparse foliage.
A 2017 study analysed the behaviour of a catastrophic release of Toxic Inhalation Hazard (TIH) materials, specifically chlorine and ammonia. Notable differences in the plumes movements in varied conditions are used to aid the development of emergency planning and response, including evacuation and shelter-in-place. 2
If a chlorine gas release occurs, evacuation is not always possible, and adequate shelters must be in place to protect personnel.