FIRE PREVENTION MEASURES
Peter F. Johnson
History tells us that fires were useful for heating and cooking but caused major damage in many cities. Many houses, major buildings and sometimes whole cities were destroyed by fire.
One of the first fire prevention measures was a requirement to extinguish all fires before nightfall. For example, in 872 in Oxford, England, authorities ordered a curfew bell to be rung at sunset to remind citizens to extinguish all indoor fires for the night (Bugbee 1978). Indeed, the word curfew is derived from the French couvre feu which literally means “cover fire”.
The cause of fires is often a result of human action bringing fuel and an ignition source together (e.g., waste paper stored next to heating equipment or volatile flammable liquids being used near open flames).
Fires require fuel, an ignition source and some mechanism to bring the fuel and ignition source together in the presence of air or some other oxidizer. If strategies can be developed to reduce fuel loads, eliminate ignition sources or prevent the fuel/ignition interaction, then fire loss and human death and injury can be reduced.
In recent years, there has been increasing emphasis on fire prevention as one of the most cost-effective measures in dealing with the fire problem. It is often easier (and cheaper) to prevent fires starting than to control or extinguish them once they have started.
This is illustrated in the Fire Safety Concepts Tree (NFPA 1991; 1995a) developed by the NFPA in the United States. This systematic approach to fire safety problems shows that objectives, such as reducing fire deaths in the workplace, can be achieved by preventing fire ignition or managing the impact of fire.
Fire prevention inevitably means changing human behaviour. This requires fire safety education, supported by management, using the latest training manuals, standards and other educational materials. In many countries such strategies are reinforced by law, requiring companies to meet legislated fire prevention objectives as part of their occupational health and safety commitment to their workers.
Fire safety education will be discussed in the next section. However, there is now clear evidence in commerce and industry of the important role of fire prevention. Great use is being made internationally of the following sources: Lees, Loss Prevention in the Process Industries, Volumes 1 and 2 (1980); NFPA 1-Fire Prevention Code (1992); The Management of Health and Safety at Work Regulations (ECD 1992); and Fire Protection Handbook of the NFPA (Cote 1991). These are supplemented by many regulations, standards and training materials developed by national governments, businesses and insurance companies to minimize losses of life and property.
Fire Safety Education and Practices
For a fire safety education programme to be effective, there must be a major corporate policy commitment to safety and the development of an effective plan that has the following steps: (a) Planning phase-establishment of goals and objectives; (b) Design and implementation phase; and (c) Program evaluation phase-monitoring effectiveness.
Goals and objectives
Gratton (1991), in an important article on fire safety education, defined the differences between goals, objectives and implementation practices or strategies. Goals are general statements of intent that in the workplace may be said “to reduce the number of fires and thus reduce death and injury among workers, and the financial impact on companies”.
The people and financial parts of the overall goal are not incompatible. Modern risk management practice has demonstrated that improvements in safety for workers through effective loss control practices can be financially rewarding to the company and have a community benefit.
These goals need to be translated into specific fire safety objectives for particular companies and their workforce. These objectives, which must be measurable, usually include statements such as:
· reduce industrial accidents and resulting fires
· reduce fire deaths and injuries
· reduce company property damage.
For many companies, there may be additional objectives such as reduction in business interruption costs or minimization of legal liability exposure.
The tendency among some companies is to assume that compliance with local building codes and standards is sufficient to ensure that their fire safety objectives are met. However, such codes tend to concentrate on life safety, assuming fires will occur.
Modern fire safety management understands that absolute safety is not a realistic goal but sets measurable performance objectives to:
· minimize fire incidents through effective fire prevention
· provide effective means of limiting the size and consequence of fire incidents through effective emergency equipment and procedures
· use insurance to safeguard against large, unforeseen fires, particularly those arising from natural hazards such as earthquakes and bushfires.
Design and implementation
The design and implementation of fire safety education programmes for fire prevention are critically dependent upon development of well-planned strategies and effective management and motivation of people. There must be strong and absolute corporate support for full implementation of a fire safety programme for it to be successful.
The range of strategies have been identified by Koffel (1993) and in NFPA’s Industrial Fire Hazards Handbook (Linville 1990). They include:
· promoting the company policy and strategies on fire safety to all company employees
· identifying all potential fire scenarios and implementing appropriate risk reduction actions
· monitoring all local codes and standards that define the standard of care in a particular industry
· operating a loss administration programme to measure all losses for comparison with performance objectives
· training of all employees in proper fire prevention and emergency response techniques.
Some international examples of implementation strategies include:
· courses operated by the Fire Protection Association (FPA) in the United Kingdom that lead to the European Diploma in Fire Prevention (Welch 1993)
· the creation of SweRisk, a subsidiary company of the Swedish Fire Protection Association, to assist companies in undertaking risk assessments and in developing fire prevention programmes (Jernberg 1993)
· massive citizen and worker involvement in fire prevention in Japan to standards developed by the Japan Fire Defence Agency (Hunter 1991)
· fire safety training in the United States through the use of the Firesafety Educator’s Handbook (NFPA 1983) and the Public Fire Education Manual (Osterhoust 1990).
It is critically important to measure the effectiveness of fire safety education programmes. This measurement provides the motivation for further programme financing, development and adjustment where necessary.
The best example of monitoring and success of fire safety education is probably in the United States. The Learn Not to Burn(Т) programme, aimed at educating the young people in America on the dangers of fire, has been coordinated by the Public Education Division of the NFPA. Monitoring and analysis in 1990 identified a total of 194 lives saved as a result of proper life safety actions learned in fire safety education programmes. Some 30% of these lives saved can be directly attributed to the Learn Not to Burn(Т) programme.
The introduction of residential smoke detectors and fire safety education programmes in the United States have also been suggested as the primary reasons for the reduction in home fire deaths in that country, from 6,015 in 1978 to 4,050 in 1990 (NFPA 1991).
Industrial housekeeping practices
In the industrial field, Lees (1980) is an international authority. He indicated that in many industries today, the potential for very large loss of life, serious injuries or property damage is far greater than in the past. Large fires, explosions and toxic releases can result, particularly in the petrochemical and nuclear industries.
Fire prevention is therefore the key to minimizing fire ignition. Modern industrial plants can achieve good fire safety records through well-managed programmes of:
· housekeeping and safety inspections
· employee fire prevention training
· equipment maintenance and repair
· security and arson prevention (Blye and Bacon 1991).
A useful guide, on the importance of housekeeping for fire prevention in commercial and industrial premises is given by Higgins (1991) in the NFPA’s Fire Protection Handbook.
The value of good housekeeping in minimizing combustible loads and in preventing exposure of ignition sources is recognized in modern computer tools used for assessing fire risks in industrial premises. The FREM (Fire Risk Evaluation Method) software in Australia identifies housekeeping as a key fire safety factor (Keith 1994).
Heat Utilization Equipment
Heat utilization equipment in commerce and industry includes ovens, furnaces, kilns, dehydrators, dryers and quench tanks.
In the NFPA’s Industrial Fire Hazards Handbook, Simmons (1990) identified the fire problems with heating equipment to be:
1. the possibility of igniting combustible materials stored nearby
2. fuel hazards resulting from unburned fuel or incomplete combustion
3. overheating leading to equipment failure
4. ignition of combustible solvents, solid materials or other products being processed.
These fire problems can be overcome through a combination of good housekeeping, proper controls and interlocks, operator training and testing, and cleaning and maintenance in an effective fire prevention programme.
Detailed recommendations for the various categories of heat utilization equipment are set out in the NFPA’s Fire Protection Handbook (Cote 1991).These are summarized below.
Ovens and furnaces
Fires and explosions in ovens and furnaces typically result from the fuel used, from volatile substances provided by the material in the oven or by a combination of both. Many of these ovens or furnaces operate at 500 to , which is well above the ignition temperature of most materials.
Ovens and furnaces require a range of controls and interlocks to ensure that unburned fuel gases or products of incomplete combustion cannot accumulate and be ignited. Typically, these hazards develop while firing up or during shut-down operations. Therefore, special training is required to ensure that operators always follow safety procedures.
Non-combustible building construction, separation of other equipment and combustible materials and some form of automatic fire suppression are usually essential elements of a fire safety system to prevent spread should a fire start.
Kilns are used to dry timber (Lataille 1990) and to process or “fire” clay products (Hrbacek 1984).
Again, this high-temperature equipment represents a hazard to its surroundings. Proper separation design and good housekeeping are essential to prevent fire.
Lumber kilns used for drying timber are additionally hazardous because the timber itself is a high fire load and is often heated close to its ignition temperature. It is essential that kilns be cleaned regularly to prevent a build-up of small pieces of wood and sawdust so that this does not come in contact with the heating equipment. Kilns made of fire-resistive construction material, fitted with automatic sprinklers and provided with high-quality ventilation/air circulation systems are preferred.
Dehydrators and dryers
This equipment is used to reduce the moisture content of agricultural products such as milk, eggs, grains, seeds and hay. The dryers may be direct-fired, in which case the productions of combustion contact the material being dried, or they may be indirect-fired. In each case, controls are required to shut off the heat supply in the event of excessive temperature or fire in the dryer, exhaust system or conveyor system or failure of air circulation fans. Again, adequate cleaning to prevent build-up of products that could ignite is required.
The general principles of fire safety of quench tanks are identified by Ostrowski (1991) and Watts (1990).
The process of quenching, or controlled cooling, occurs when a heated metal item is immersed in a tank of quenching oil. The process is undertaken to harden or temper the material through metallurgical change.
Most quenching oils are mineral oils which are combustible. They must be chosen carefully for each application to ensure that the ignition temperature of the oil is above the operating temperature of the tank as the hot metal pieces are immersed.
It is critical that the oil does not overflow the sides of the tank. Therefore, liquid level controls and appropriate drains are essential.
Partial immersion of hot items is the most common cause of quench tank fires. This can be prevented by appropriate material transfer or conveyor arrangements.
Likewise, appropriate controls must be provided to avoid excessive oil temperatures and entry of water into the tank that can result in boil-over and major fire in and around the tank.
Specific automatic fire extinguishing systems such as carbon dioxide or dry chemical are often used to protect the tank surface. Overhead, automatic sprinkler protection of the building is desirable. In some cases, special protection of operators who need to work close to the tank is also required. Often, water spray systems are provided for exposure protection for workers.
Above all, proper training of workers in emergency response, including use of portable fire extinguishers, is essential.
Chemical Process Equipment
Operations to chemically change the nature of materials have often been the source of major catastrophes, causing severe plant damage and death and injury to workers and surrounding communities. Risks to life and property from incidents in chemical process plants may come from fires, explosions or toxic chemical releases. The energy of destruction often comes from uncontrolled chemical reaction of process materials, combustion of fuels leading to pressure waves or high levels of radiation and flying missiles that can cause damage at large distances.
Plant operations and equipment
The first stage of design is to understand the chemical processes involved and their potential for energy release. Lees (1980) in his Loss Prevention in the Process Industries sets out in detail the steps required to be undertaken, which include:
· proper process design
· study of failure mechanisms and reliability
· hazard identification and safety audits
· hazard assessment-cause/consequences.
The assessment of the degrees of hazard must examine:
· potential emission and dispersal of chemicals, particularly toxic and contaminating substances
· effects of fire radiation and dispersal of combustion products
· results of explosions, particularly pressure shock waves that can destroy other plants and buildings.
More details of process hazards and their control are given in Plant guidelines for technical management of chemical process safety (AIChE 1993); Sax’s Dangerous Properties of Industrial Materials (Lewis 1979); and the NFPA’s Industrial Fire Hazards Handbook (Linville 1990).
Siting and exposure protection
Once the hazards and consequences of fire, explosion and toxic releases have been identified, siting of chemical process plants can be undertaken.
Again, Lees (1980) and Bradford (1991) provided guidelines on plant siting. Plants must be separated from surrounding communities sufficiently to ensure that those communities cannot be affected by an industrial accident. The technique of quantitative risk assessment (QRA) to determine separation distances is widely used and legislated for in the design of chemical process plants.
The disaster in Bhopal, India, in 1984 demonstrated the consequences of locating a chemical plant too close to a community: over 1,000 people were killed by toxic chemicals in an industrial accident.
Provision of separating space around chemical plants also allows ready access for fire-fighting from all sides, regardless of wind direction.
Chemical plants must provide exposure protection in the form of explosion-resistant control rooms, worker refuges and fire-fighting equipment to ensure that workers are protected and that effective fire-fighting can be undertaken after an incident.
Spills of flammable or hazardous materials should be kept small by appropriate process design, fail-safe valves and appropriate detection/control equipment. However, if large spills occur, they should be confined to areas surrounded by walls, sometimes of earth, where they can burn harmlessly if ignited.
Fires in drainage systems are common, and special attention must be paid to drains and sewerage systems.
Heat transfer hazards
Equipment that transfers heat from a hot fluid to a cooler one can be a source of fire in chemical plants. Excessive localized temperatures can cause decomposition and burn out of many materials. This may sometimes cause rupture of the heat-transfer equipment and transfer of one fluid into another, causing an unwanted violent reaction.
High levels of inspection and maintenance, including cleaning of heat transfer equipment, is essential to safe operation.
Reactors are the vessels in which the desired chemical processes are undertaken. They can be of a continuous or batch type but require special design attention. Vessels must be designed to withstand pressures that might result from explosions or uncontrolled reactions or alternatively must be provided with appropriate pressure-relief devices and sometimes emergency venting.
Safety measures for chemical reactors include:
· appropriate instrumentation and controls to detect potential incidents, including redundant circuitry
· high quality cleaning, inspection and maintenance of the equipment and the safety controls
· adequate training of operators in control and emergency response
· appropriate fire suppression equipment and fire-fighting personnel.
Welding and Cutting
The Factory Mutual Engineering Corporation’s (FM) Loss Prevention Data Sheet (1977) shows that nearly 10% of losses in industrial properties are due to incidents involving cutting and welding of materials, generally metals. It is clear that the high temperatures required to melt the metals during these operations can start fires, as can the sparks generated in many of these processes.
The FM Data Sheet (1977) indicates that the materials most frequently involved in fires due to welding and cutting are flammable liquids, oily deposits, combustible dusts and wood. The types of industrial areas where accidents are most likely are storage areas, building construction sites, facilities undergoing repair or alteration and waste disposal systems.
Sparks from cutting and welding can often travel up to 10 m and lodge in combustible materials where smouldering and later flaming fires can occur.
Arc welding and arc cutting are examples of processes involving electricity to provide the arc that is the heat source for melting and joining metals. Flashes of sparks are common, and protection of workers from electrocution, spark flashes and intense arc radiation is required.
Oxy-fuel gas processes
This process uses the heat of combustion of the fuel gas and oxygen to generate flames of high temperature that melt the metals being joined or cut. Manz (1991) indicated that acetylene is the most widely used fuel gas because of its high flame temperature of about .
The presence of a fuel and oxygen at high pressure makes for an increased hazard, as is leakage of these gases from their storage cylinders. It is important to remember that many materials that do not burn, or only burn slowly in air, burn violently in pure oxygen.
Safeguards and precautions
Good safety practices are identified by Manz (1991) in the NFPA Fire Protection Handbook.
These safeguards and precautions include:
· proper design, installation and maintenance of welding and cutting equipment, particularly storage and leak testing of fuel and oxygen cylinders
· proper preparation of work areas to remove all chance of accidental ignition of surrounding combustibles
· strict management control over all welding and cutting processes
· training of all operators in safe practices
· proper fire-resistant clothing and eye protection for operators and nearby workers
· adequate ventilation to prevent exposure of operators or nearby workers to noxious gases and fumes.
Special precautions are required when welding or cutting tanks or other vessels that have held flammable materials. A useful guide is the American Welding Society’s Recommended Safe Practices for the Preparation for Welding and Cutting of Containers that have held Hazardous Substances (1988).
For building works and alterations, a UK publication, the Loss Prevention Council’s Fire Prevention on Construction Sites (1992) is useful. It contains a sample hot-work permit to control cutting and welding operations. This would be useful for management in any plant or industrial site. A similar sample permit is provided in the FM Data Sheet on cutting and welding (1977).
Lightning is a frequent cause of fires and deaths of people in many countries in the world. For example, each year some 240 US citizens die as a result of lightning.
Lightning is a form of electrical discharge between charged clouds and the earth. The FM Data Sheet (1984) on lightning indicates that lightning strikes may range from 2,000 to 200,000 A as a result of a potential difference of 5 to 50 million V between clouds and the earth.
The frequency of lightning varies between countries and areas depending on the number of thunderstorm-days per year for the locality. The damage that lightning can cause depends very much on the ground condition, with more damage occurring in areas of high earth resistivity.
The NFPA 780 Standard for the Installation of Lightning Protection Systems (1995b) sets out the design requirements for protection of buildings. While the exact theory of lightning discharges is still being investigated, the basic principle of protection is to provide a means by which a lightning discharge may enter or leave the earth without damaging the building being protected.
Lightning systems, therefore, have two functions:
· to intercept the lightning discharge before it strikes the building
· to provide a harmless discharge path to earth.
This requires buildings to be fitted with:
· lightning rods or masts
· down conductors
· good ground connections, typically 10 ohms or less.
More details for the design of lightning protection for buildings is provided by Davis (1991) in the NFPA Fire Protection Handbook (Cote 1991) and in the British Standards Institute’s Code of Practice (1992).
Overhead transmission lines, transformers, outdoor substations and other electrical installations can be damaged by direct lightning strikes. Electrical transmission equipment can also pick up induced voltage and current surges that can enter buildings. Fires, damage to equipment and serious interruption to operations may result. Surge arresters are required to divert these voltage peaks to ground through effective earthing.
The increased use of sensitive computer equipment in commerce and industry has made operations more sensitive to transient over-voltages induced in power and communication cables in many buildings. Appropriate transient protection is required and special guidance is provided in the British Standards Institute BS 6651:1992, The Protection of Structures Against Lightning.
Proper maintenance of lightning systems is essential for effective protection. Special attention has to be paid to ground connections. If they are not effective, lightning protection systems will be ineffective.