Prevention of fires and explosions

Introduction

Fire can occur when flammable material, oxygen and sufficient ignition energy are available. Explosion depends on an atmosphere of a mixture of flammable material with oxygen. The best approach to prevent fires and explosions is to substitute or minimise the use of flammable material. If that is not possible it is important to avoid any source of ignition. The manufacturing, processing or storage of explosives is not covered in this article.

Importance

According to the World Fire Statistics Centre the costs of fires and explosions are estimated at approximately 1 per cent of global Gross Domestic Product per year, with the death toll in Europe alone reaching several thousand^[1].

Fires and explosions in industrial structures and plants may not only lead to losses and damages but may also hamper the functioning of the economy. According to the accident insurer for the chemical industry and similar sectors, an average of three explosions take place every day in Germany; fortunately, most of these explosions remain without serious consequences because companies have taken sufficient risk mitigation measures^[2]. The eMARS database^[3] contains reports of chemical accidents and near misses. eMARS stands for Major Accident Reporting System. EU Member States are obliged to submit an accident report when an incident occurs at a chemical plant that meets the criteria of a 'major accident' as defined by the Seveso III Directive (2012/18/EU)^[4]. The purpose of the eMARS database is to facilitate exchange of lessons learned from accidents and near misses involving dangerous substances in order to improve chemical accident prevention and mitigation of potential consequences. In total, the database contains more than 1,100 reports of accidents, nearly 45% of which involve an explosion^[5].

Fires and explosions

Fire is a rapid oxidation of material releasing heat, light and various chemical products. The fire triangle describes the conditions that have to be met in order a fire can start: (1) flammable material, (2) oxygen, (3) energy to ignite the fire.

All material capable of an exothermic oxidation reaction has to be considered as flammable. This can be:

• gases such as butane, propane, methane, carbon monoxide, hydrogen;
• liquids such as fuels, solvents, oils, greases, paints and thinners;
• solids such as wood, coal, plastics, metals, food.

Oxygen is usually available in sufficient quantities in the air to get a fire started and to sustain it. Fires may however start much easier and may be more powerful in terms of flame volume and released energy, if the oxygen level of the surrounding atmosphere is increased, e.g. when an oxygen cylinder leaks or bursts or when oxygen releasing substances (e.g. peroxides) are present.

The amount of ignition energy needed to start a fire can be very low (usually with gases) or  quite high, which is usually the case with solids. Liquids are often somewhere in between. However the ignition of solids or aerosols depends also on the particle size: fine dusts of e.g. aluminium or flour mixed with air can explode easily.

An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave^[6]. When the shock wave created by the explosion is greater than the speed of sound, the term detonation is used; if the speed is less, the term deflagration is used^[7].

Occupational safety and health management

Employers have a legal duty to ensure the safety and health of workers and to put in place suitable arrangements and defining the roles and responsibilities of everyone involved (OSH management).  This includes ensuring that health and safety staff have the necessary knowledge to carry out a risk assessment to identify fire and explosion hazards, assess the risks and determine effective measures. If there is a lack of competencies in-house, the employer must call upon external services/persons for providing assistance^[8]. 

On determining the company processes, fire risks as well as fire prevention and fighting measures have to be considered already in the design phase. In collaboration with architects and fire prevention experts this may include: indicating fire compartments, separation of special units, extinguisher systems and escape routes.

Ensuring qualification and training of all employees involved in fire prevention and fire-fighting tasks is another important management issue. This has to include regular fire drills and should also involve demonstrations of how easily fires can develop presented by the fire brigade or related institutions. Employees should be given the opportunity to not only develop their knowledge but to also bring in their experience. This is all the more important as also unplanned and unforeseeable dangerous situations and the behaviour of workers need to be considered. However in this aspect it is also of foremost importance that all managers set a good example and always follow the rules themselves.

Good management should also seek advice from outside experts where necessary, provide for effective monitoring, allow opportunities to learn from experience by analysing fires and risky situations and thus create continuous improvement processes. Finally all important aspects should be documented for further reference. In order to have a comprehensive structure, employers should consider implementing an OSH management system, this could even be integrated into a quality and environment management system so as to make use of synergy effects.

In case of high risk situations, it may be necessary to put a 'permit to work' system in place, only giving specifically trained people access to high risk areas. Coordinating panels involving e.g. contractors on the premises have to be set up and means and ways of communication between all stakeholders need to be established carefully.

The situation in small and medium enterprises can be quite different from that of larger firms. These may be service companies doing e.g. maintenance work for larger companies or individual customers (e.g. garages). From their point of view, it is important to have always the right contact persons, to be involved in the client’s risk assessment processes, to be always up to date regarding developments of the contractor’s buildings and machines, to have the right equipment and to receive sufficient training.

Identification of fire and explosion risks

Companies have to conduct risk assessments. A risk assessment is a careful examination of what, in any institution, could cause harm to people, so that one can judge whether there are enough precautions in place, or more is needed to prevent harm. It involves identifying the hazards present in any undertaking (whether arising from work activities or from other factors, e.g. the layout of the premises) and then evaluating the extent of the risks involved, taking into account existing precautions^[9].

Factors to consider in fire risk assessment are^[10]:

• the nature of the activities;
• what substances are used, what processes, what installations are present and any interactions that may occur; 
• the maximum number of workers present on site, as well as visitors, clients, contractors, patients, etc;
• the location of the various premises, storage areas, buildings;
• work carried out by contractors;
• etc.

Fire

Fire can harm workers and the public not only by causing burns but also by heat, fire gases, smoke and weakening structures and it may cause explosions if explosive atmospheres can develop.

Of foremost importance regarding any fire and explosion risk assessment, is to identify flammable substances in the company. These may include flammable liquids, gases, aerosols, solids, dusts, substances that may ignite spontaneously (e.g. textiles with decomposing greases and fats), substances that develop flammable gases on contact with water or other chemicals, explosives, oxidising substances (e.g. peroxides). It has also to be established as to whether there are any working processes that may release any of the above-mentioned substances (e.g. dusts, mixture of chemicals). For all the identified substances all relevant characteristics, like flash points, vapour pressure, calorific value, explosion limits, etc. should be established.

It is also necessary to clarify, who is working with these substances, in which processes and for how long. Not only the normal work procedures have to be analysed but also servicing, test runs, malfunctioning of machines and plants as well as unauthorised access.

Are there ignition sources like open flames and high temperatures available or may they develop during work processes? Such ignition sources can be:

• Thermal energy: combustion engines, open fire, hot surfaces, welding sputters, laser;
• Electric energy: short circuits, electric arcs, electromagnetic radiation, lightning, electrostatic, heat developed by currents;
• Mechanical energy: friction, ultrasound, compression, sparks from tools, grinding;
• Chemical energy: spontaneous heating or igniting, catalytic reactions, accelerating exothermal reactions.

Also, ignition sources from external factors should be considered such as natural external sources (lightning, forest fires, etc.) and arson. 

On having gathered and analysed all relevant information, the risk assessment team has to evaluate the extent of the risks involved. The evaluation can be based on qualitative or quantitative methods. An introduction to a qualitative method for assessing fire risk for people or property is available in a guide developed by the Confederation of Fire Protection Associations Europe (CFPA-Europe) ^[11]. An example of a quantitative method is the ISO standard 16732 on Fire safety engineering, Guidance on fire risk assessment.

A high risk is indicated by larger amounts of flammable or oxidising substances and by a certain probability of a fire outbreak whereby a fast spread of the fire or big amounts of smoke and heat can be expected. This may be the case for sectors like: petrochemistry, chemical industry, electroplating, light metal processing, printing industry, rubber industry, wood processing, mills and silos, garages, food industry.

Explosion

If flammable substances, as specified above, exist in the company, the employer has to establish as to whether the development of an explosive atmosphere is possible. Such an atmosphere is defined as a mixture of oxygen with flammable substances, whereby this can include not only gases or aerosols from liquids but also particles from solid matter. For example a cloud of dust from flour or other biologic material, as well as from metal fines, can also explode and cause severe damage^[12]. In the next step it has to be established if this atmosphere can develop in such amounts that it would need special measures.

Results

The risk assessment has also to consider the organisation of the company, any individuals identified as being particularly at risk and the fire or explosion measures already in place. It has to be concluded whether these measures are sufficient or would need changes and improvements. The implementation may mean making changes to the organisation and working procedures, working environment, equipment and products used; training management and staff; and improving communications. The findings have to be recorded.

Measures

The adoption of any policies and measures should always be carefully planned, and carried out with consultation of the workforce and their representatives as a key component of success. This should include coordination and communication between contractor and possible service company personnel. The general principle, also laid down in the relevant EU directives, is that risks should be prevented at source and that work organisation, tasks, equipment and tools should be adapted to workers in order to eliminate and reduce risks. Measures should follow the prevention hierarchy:

1. elimination of risks;
2. substitution e.g. of dangerous and flammable substances;
3. collective control measures like avoidance of effective ignition sources;
4. individual control measures such as personal protective equipment.

There have to be periodic reviews to check that measures, policies and procedures remain appropriate and are working. They have to be revised if necessary.

The table below includes examples of preventive measures to reduce the risk of the occurrence of fire.

Table 1: Fire risks and preventive measures 

Source: Adapted from^[8]

Preventive measures regarding explosions

These measures would firstly have to focus on the avoidance of explosive atmospheres mainly by substituting or reducing flammable and oxidising substances (see table 1). Also mixtures with inert gases can sometimes be applied for dilution. If that is not possible, the employer has to take additional measures to protect the workers, classify the zones with explosive atmospheres according to the ATEX Directive 99/92/EC and draw up an explosion protection document ^[13]. “After assigning and indicating the zones, the next step is to ensure that effective ignition sources are avoided by using specified equipment/machines for the different zones (non-sparking equipment). Equipment is categorised in 1, 2 or 3 depending on the ATEX zone where it is intended to be used (0/20, 1/21, 2/22). Such equipment has to comply with Directive 2014/34/EU.^[14] 

Table 2: Zones according to ATEX

If it is still not possible to effectively prevent the ignition of the explosive atmospheres, the employer has to implement measures that limit the effects of explosions to a harmless level. These measures can be: explosion-resistant construction, explosion venting (e.g. bursting discs), explosion suppression (rapid injection of extinguishing agents) or explosion isolation.

All these steps have to be documented, put into an explosion protection document and shown to the authorities on demand.

Measures in case of an accident

Especially the large fires and explosions in firms (e.g. explosions in a chemical company in Rotterdam in early 2011) indicate how important it is to have safe systems in place. On the other hand it also shows that it is equally important to be prepared when accidents happen. Such emergency plans include appropriate emergency procedures, assigning tasks and responsibilities, first aid arrangements, firefighting equipment and evacuation plans. This should be established based on the company’s risk assessment and involve qualified staff. Exercises should be conducted regularly.

Legislation

On the basis of the OSH Framework directive (89/391/EEC) a series of individual directives were adopted. Directives that are particularly relevant for this topic are:

• Directive 1999/92/EC of 16 December 1999 on minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres (15th individual Directive within the meaning of Article 16(1) of Directive 89/391/EEC)13. The EU Commission has also issued non-binding guidance with practical information om how to implement the legal provisions. ^[15]
• Directive 92/58/EEC of 24 June 1992 on the minimum requirements for the provision of safety and/or health signs at work (ninth individual Directive within the meaning of Article 16 (1) of Directive 89/391/EEC)^[16]
• Directive 98/24/EC of 7 April 1998 on the protection of the health and safety of workers from the risks related to chemical agents at work (fourteenth individual Directive within the meaning of Article 16(1) of Directive 89/391/EEC)^[17]

There are two so called ATEX (Atmosphères Explosives) directives, one for the manufacturer of explosion proof equipment (Directive 2014/34/EU) and one for the employer aimed at protecting the workers (ATEX workplace Directive 1999/92/EC).