NEBOSH National Fire Certificate - ACT Associates · NEBOSH National Fire Certificate Unit FC1 Fire safety and risk management ... establish the source and likelihood that a fire

NEBOSH National Fire Certificate

Unit FC1 Fire safety and risk management

Sample pages from

E2

Principles of fire and explosion

E4

Fire protection in buildings

E5

Safety of people in the event of fire

E6 Fire safety risk assessment

PRINCIPLES OF FIRE AND EXPLOSION - ELEMENT 2

2.1 - The principles of the combustion process in relation to fire The concept of the fire triangle A simple approach depicts fire as having three essential components - fuel, oxygen and heat. When the three separate parts are brought together a fire occurs. This is often depicted by the ‘fire triangle’. This traditional approach is useful when considering the ‘ingredients’ needed to make a fire.

Combustion THE CHEMISTRY OF COMBUSTION Combustion is defined as being a chemical reaction during which heat energy and light energy are emitted. If the above three components form together in the right proportions, then the chemical reaction of combustion takes place. Once a fire starts a self-sustaining chain reaction begins at the surface of the fuel (solid or liquid) which turns into a vapour, which is what burns in the combustion process.

Figure 2-1: The fire triangle. Source: RMS/CorelDRAW! 5.0 Clipart.

A similar process occurs with the molecules of a gas, but because the collective surface area of the molecules is large the combustion process is very fast. A fire may be defined as a chemical chain reaction in which fuel is reduced by reaction with an oxidiser to produce light, heat and combustion products. CHEMICAL REACTIVITY Endothermic Chemical reactions that must absorb energy in order to proceed are called endothermic reactions. Endothermic reactions cannot occur spontaneously, work must be done in order to get these reactions to occur. When endothermic reactions absorb energy a temperature drop is measured. Endothermic reactions are not generally considered an issue in relation to fire, but this is not always the case. For example, if a fire was to take place in the vicinity of an acetylene cylinder heat released from the fire would be absorbed into the cylinder leading to the endothermic decomposition of the acetylene/acetone mixture inside the cylinder and the potential for a supersonic explosion to occur. Exothermic Many chemical reactions release energy in the form of heat, light, or sound. These are exothermic reactions. As can be seen by the explanation of the chemistry of combustion, combustion involves an exothermic reaction. Exothermic reactions may occur spontaneously. Some exothermic reactions produce heat very quickly resulting in an explosion. A particularly significant example of an exothermic reaction would be those arising from fires involving organic peroxides. These products are dangerous in a fire as they readily give off quantities of oxygen. The chemical process taking place for this to happen gives out quantities of heat. If these products are affected by a fire the entire process is accelerated. THE CONDITIONS FOR THE MAINTENANCE OF COMBUSTION Fuel The fuel dictates all aspects of combustion. The type of fuel, the form the fuel is in, or how much is

present in the air will influence its susceptibility to combustion. Heat The amount of heat required to cause ignition is dictated by the form (solid, liquid, vapour or gas) and

type of fuel. Oxygen Oxygen is provided from the air around us. Other than in specialised industrial applications it is always

present. (Note: If oxygen levels drop below 15% the combustion process stops). Consideration should be given to how the available oxygen might inadvertently be increased (oxygen enrichment) via oxidising agents or oxygen cylinders. (Note: A 2% increase in oxygen levels to 23% is sufficient to accelerate the combustion process).

For the combustion process to be maintained all three of the component parts above must remain present. If one or more of these parts of the fire is removed, the fire will be extinguished. This can be done by: 1. Cooling the fire to remove the heat, for example, by use of a water or foam extinguisher. 2. Starving the fire of fuel, for example, isolation of a gas supply. 3. Smothering the fire by limiting its oxygen supply, for example, by use of a carbon dioxide or foam extinguisher. 4. Chemical interference of the flame reactions, for example, the method by which some extinguishing media work,

typically wet chemical extinguishing agents.

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FIRE PROTECTION IN BUILDINGS - ELEMENT 4

© RMS 85

4.4 - Selection procedures for basic fire extinguishing methods for both life risk and process risk

Portable fire-fighting equipment and fixed installations CLASSIFICATION OF FIRES WHEN CHOOSING FIRE-FIGHTING EQUIPMENT A basic understanding of the classes of fire needs to be understood in order to provide and use the correct fire fighting system and equipment for the likely fires that will occur in premises. In addition many portable fire-fighting equipment (fire extinguishers) state the classes of fire for which they are suitable.

CLASS A

Fires involving solids (wood, paper, plastics, etc., usually of an organic nature). You must provide a minimum number of fire fighting equipment for a class A fire to comply with BS5306: Part 8; 2000 (Code of Practice) - fire extinguishing installations and equipment on premises.

The basic provision for extinguishers is a minimum of 2 extinguishers per floor for floor area up to 400m2 with a minimum total rating of 26A.

For floor areas over 400m2, the total Class A ratings worth of extinguishers should be no less than 0.065 x floor area of storey (m2), with a minimum of two extinguishers.

However in small single occupancy buildings with an upper floor area not exceeding 100m2 a minimum rating of 13A may be sufficient.

Class A fire rating required = 0.065 x floor area (m2). CLASS B

Fires involving liquids or liquefiable solids (petrol, oil, paint, wax, etc.). The provision of extinguishers for a Class B risk is more complicated. The workplace needs to be assessed as follows:

Each room or enclosure should be considered separately. Spillage risks should be assessed, with a Class B extinguisher rating provided

equal to 10 x the volume of perceived spillage in litres. Open topped containers more than 20 metres apart should be considered

separately. Fire risks sited within 20 metres of another open topped container should be assessed as either an undivided or a divided group. In all cases when open topped containers are involved, a surface risk area is calculated and charts used to provide the necessary fire rating requirements.

CLASS C

Fires involving gases (liquefied petroleum gas, natural gas, acetylene, etc.). There are no calculations for the number of extinguishers required for Class C fires, as the only safe method of extinguishment is to cut off the supply of gas. Extinguishers can be used to extinguish gas fires, but only in combination with isolation of the supply.

CLASS D

Fires involving metals (zinc, sodium, magnesium, aluminium and many metal powders and swarf, etc.). There are no generic calculations available to work out the number of extinguishers required, as each case will depend upon the type and amount of metal available and the extinguishing product chosen.

ELECTRICAL HAZARDS

Although not a class of fire, fires in live electrical equipment cause an additional hazard requiring special consideration and the provision of suitable fire fighting equipment. This is a pictogram/statement used with extinguishers to identify their suitability for use on electrical equipment. Note: that this symbol on a water based extinguisher does not denote the extinguisher is safe to use on the 'live' electrical equipment, but only that if the extinguishing product inadvertently contacts the 'live' electrics that the user should not be harmed.

CLASS F

Fire involving cooking fats/oils. The number of extinguishers required is dictated by the size of pan/surface area available to burn. A typical 75F rated extinguisher will only cover up to 0.11m2 area and 2x75F extinguishers will cover up to 0.4m2 area. If deep fat fryers etc have an open surface area larger than 0.4m2, then a fixed fire fighting system should be installed.

Figure 4-35: Classification of fires. Source: Rivington designs/FSTC.

ELEMENT 5 - SAFETY OF PEOPLE IN THE EVENT OF FIRE

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Ensuring the plan is reviewed regularly and whenever a change is proposed to layout, replacement of equipment, the introduction of new substances or people into the workplace.

An understanding of the fire safety protective and preventive systems that are in place in the workplace and an awareness of the legality of these issues that is relevant to their individual role within the management structure.

Exam practice

1. Explain the requirements for ensuring that access to premises and facilities for the fire service are provided and maintained. (8)

2. An organisation uses the fire marshal system for the safe evacuation of the premises.

(a) Explain how a fire marshal system operates. (5)

(b) Outline the benefits with respect to human behaviour. (3)

3. Outline the factors to be considered when developing an evacuation procedure for a shared occupancy office building. (8)

4. (a) Outline the purpose of a fire emergency plan. (2)

(b) Outline the content that should be included in a fire emergency plan. (6)

5. A waste bin in a clothing retail store is on fire. One customer panics and sprints out of the store after seeing flames. Another customer becomes hysterical after smelling smoke. A third customer activates the alarm and calmly leaves through a fire exit. The fire warden moves clothing racks away from the burning bin and uses an extinguisher to put out the fire. Identify FOUR principles of perception AND give an example from the description above for EACH principle. (8)

6. (a) Identify THREE categories of persons who may need to have either a personal emergency evacuation plan (PEEP) or who may need particular assistance in order to reach a place of safety in the event of a fire in a workplace. (3)

(b) Outline ways that could be adopted to assist vulnerable persons to reach a place of safety in the event of a fire. (5)

7. (a) Identify possible fuel sources AND ignition sources that may be identified when undertaking a fire risk assessment within a hospital. (12)

(b) Give reasons why a phased evacuation system may be appropriate in a hospital premises. (3)

(c) Outline how a phased evacuation system might operate. (5)

8. Give reasons why a person may be slow to evacuate a building when the fire alarm has been activated. (8)

9. A fire training session for employees could include information on the fire triangle, classes of fire, fire risk assessment and fire legislation. Outline EIGHT additional topics that could be included in a fire safety training session for employees. (8)

10. A fire alarm was activated by an automatic detector in the kitchen area of a cafeteria during a busy lunchtime period, while customers were either queuing for or eating their meals.

(a) Outline ways in which customers may react to the fire alarm in this situation. (4)

(b) Outline the issues to be addressed to assist in the safe evacuation of the customers from the cafeteria. (4)

11. Identify FOUR component parts of a fire alarm system AND outline the function of EACH. (8)

Please refer to the ‘exam practice answers’ section located at the back of this book.

FIRE SAFETY RISK ASSESSMENT - ELEMENT 6

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6.1 - Aims and objectives of fire safety risk assessments A fire risk assessment is an organised and methodical examination of premises along with the activities carried on to establish the source and likelihood that a fire could start and cause harm to those in/or around the premises.

Meaning of hazard and risk in relation to a fire HAZARD “Something that has the potential to cause harm (loss)” “Anything that has the potential to cause harm.” Figure 6-1: Hazard - definition. Source: Fire safety risk assessment - offices and shops, DCLG. In this case the main interest is hazards that have potential to cause harm through fire or explosion. Consideration should be given to fire hazards around the workplace, such as electrical equipment plugged in, a task such as grinding that causes sparks or large stocks of combustible materials being present.

Figure 6-2: Hazard - 4 way extension lead. Source: FSTC.

Figure 6-3: Misuse of extensions - increased risk. Source: FSTC.

RISK “The likelihood of a given loss occurring in defined circumstances” “The chance of that harm occurring.” Figure 6-4: Risk - definition. Source: Fire safety risk assessment - offices and shops, DCLG.

For example, the risk from an overloaded electrical circuit (when a multiple socket device is used to power other devices that cumulatively exceed the rated current capacity of the multiple socket device) is the likelihood that it will lead to a fire. This will depend upon: a) The circumstances presented by the hazard. b) How it is controlled. c) Who is exposed to the hazard. In the example of an overloaded circuit, major determining factors are, how long the overload exists, any over current devices that may limit its effect, and its relative location to sources of fuel and people. When considering 'risk', the potential consequences, should the risk materialise, need to be taken into account. For example, the consequences of the electrical equipment shown in figure refs 6-2 and 6-3 igniting should not be immediately life threatening (although this could occur depending upon the location of this equipment and the time taken to detect the fire). Whereas, the consequences of a gas leak of acetylene being ignited in a workplace could create a detonating explosion and instantly cause death and injury to people in the vicinity.

Criteria for a 'suitable and sufficient risk assessment’ In order to be suitable and sufficient a risk assessment must: 1) Identify all the significant hazards and evaluate the risks from those hazards, taking into account current legal

requirements. 2) Identify any group of employees or single employees who are especially at risk. 3) Identify others who may be specifically at risk, for example, members of the public, visitors. 4) Evaluate existing controls, stating whether or not they are satisfactory, and if not, the action necessary. 5) Evaluate the need for further controls including information, instruction and training. 6) Record the significant findings. 7) Be carried out by competent person(s) who have the necessary experience or training in hazard identification and

carrying out risk assessments, knowledge of the process or activity, and good communication and reporting skills.