Safety in the Use of ChemicalsChapter 8Control of Major Industrial Accidents |
What is a major accident?
Chemicals which are very toxic or have the potential to cause fires and explosions can pose serious hazards to life and the well-being of those working with them or living near where they are used or stored. Chemicals have caused tragedies in which dozens and sometimes thousands of human lives have been lost. Such accidents have led safety experts to devise special terms to describe events and substances which can provoke accidents.
A major accident is any unexpected event involving fire, explosion or toxic release because of industrial activity, usually involving chemicals. It has to be serious enough to threaten the lives of the workers and the surrounding population, and may have a dangerous impact on the environment. Any enterprise or establishment which stores, uses or produces materials with the potential to cause a major accident is called major hazard installation. Such establishments must observe certain procedures to avert the possibility of an accident and everyone, especially those living in the surrounding areas, must be aware of their existence.
How do we identify a major hazard installation?
| Some accidents involving chemicals have resulted in terrible losses of human life and damage to the environment, prompting special efforts by experts to prevent and deal with such accidents. |
Many industries use varying amounts of chemicals with potential risks of fires, explosions or health and environmental hazards. Should all of them be declared major hazard installations? There is no exact answer, but the European Community (EC) has established criteria which can be used as a yard stick to find out if an enterprise poses a major hazard. These criteria are based upon the potential of the materials to cause fires, explosions or toxic releases.
A threshold has been fixed for about 180 chemicals, which ranges from a few kilograms to several thousand tonnes of the material, depending on its toxicity and flammability. As soon the quantity exceeds the threshold, the enterprise becomes a major hazard installation and special measures have to be adopted to safeguard the workers, the surrounding population and the environment. The exact definitions may vary from country to country. Some examples of the substances, their threshold quantities and the sites where they are likely to be found are given in Table 8.1.
Table 8.1 Examples of materials likely to cause major accidents, their threshold quantities
and the activities or industries where they are likely to be found
| Type of hazard | Examples of materials | Threshold quantity | Industries or where likely to be found |
| Very toxic | Methyliso-cyanate
Phosgene |
150 Kg
750 Kg |
Pesticide manufacture
Manufacture of dyestuffs and some insecticides |
| Toxic | Ammonia
Chlorine Carbon disulphide |
500 tonnes
25 tonnes 200 tonnes |
Fertilizer, soda ash and pharmaceutical industries
Caustic soda production, textile industry, pesticides and plastic manufacture Viscose rayon manufacture, oil extraction |
| Flammable gases | Methane (natural gas) | 200 tonnes | Fertilizer and ammonia manufacture |
| Flammable liquids | Gasoline, acetone, white spirit | 50,000 tonnes | Petrochemical and refining enterprises, fuel storage sites |
| Special flammable materials | Hydrogen | 50 tonnes | Fertilizer, ammonia, hydrogenated oils and petrochemicals manufacture |
| Explosive materials | Ammonium nitrate | 2500 tonnes | Fertilizer production and storage |
Reporting major hazard installations
It most countries it is required under law for the management of an enterprise to inform the authorities if their enterprise has the potential to cause a major hazard. These authorities are usually the government agencies concerned with the workers' welfare, fire fighting, civil defence, local administration, environmental protection or other agencies established by the government for such purposes. The information should be presented in such a way that the potential risks and safety measures to be taken are easily identified. The information should clearly state the likely impact on the workers, local population and the environment in the event of a major accident.
Large quantities of chlorine gas produced in a chloralkali plant, if released, can cause a major accident with devastating consequences.
Management of installations
The primary responsibility for averting the occurrence of major industrial accidents falls on the people running such installations. They should keep in mind that things can go wrong with machines, human beings can make errors of judgement, or unexpected events like earthquakes or hurricanes can strike. It is the responsibility of the management to be prepared for all possible emergency situations. They should take workers and if necessary the surrounding population into their confidence and prepare them for actions to be taken in case of an emergency. The first priority should be to select safer materials, equipment and practices. Workers must also extend full co-operation in running operations safely and must be aware of the consequences of any major accident for themselves, their colleagues and the population.
What the authorities should do
A number of agencies are established by each government to safeguard the interests of its citizens and ensure protection of their lives and property. Major hazard installations are becoming commonplace. Some of them are located in the middle of thickly populated areas. Governments should adopt a policy and legislation to deal with such operations and ensure their safe operation. The authorities should be prepared to co-ordinate emergency actions in case of an accident.
The first priority should be to prepare an inventory of such installations, keep it updated and have all information ready regarding types and quantities of hazardous materials, protective measures in place, and such measures as evacuation of the population, first-aid and fire fighting, to be taken in case of the emergencies. There should be a clear policy regarding the location of such installations and permission for people to live around such installations.
Planning for emergencies
No matter how safe an installations may be, there is always a possibility that something may go wrong. It may be a human error. Or it may be failure of a plant mechanism. Sometimes natural forces like earthquakes, floods or lightening may spark off a chain of events leading to a major accident. It is essential that those managing a major hazard installation are always prepared for emergency situations.
Actual arrangements depend on the types and quantities of the hazardous substances involved and the likely impact on people and the environment. The more serious the consequences, more elaborate the planning has to be. Responsibility for such planning falls mainly on the management of the enterprise, but the government agencies have a major role to play.
Workers should be trained through frequent rehearsals of the steps to be taken in case of a major accident; people should be nominated who will co-ordinate emergency responses such as shutting down operations, calling assistance from outside, firefighting, and informing the public at the time of actions to be taken for their protection.
The role of the authorities is crucial in managing emergencies. They have to inspect the major hazard installations frequently to make sure the safety measures adopted are adequate to avert an emergency. Authorities must also play a key role evacuation of the population, medical treatment of the affected people, firefighting, and minimizing the impact of the accident on the environment.
Exercise
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