NEBOSH Certificate in fire safety downloadable PDF V13 (1) …

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NEBOSH Certificate in Fire Safety Element E1: Managing Fire Safety Learning outcomes E1.1 The learner will be able to justify fire safety improvements using moral and financial arguments. E1.2 The learner will be able to explain how fire safety is regulated and the roles of national government and international bodies. Introduction When you have worked through all of the following elements and sections on the subject of 'Fire' you will have covered a variety of topics in quite some depth and will have studied elements of law, science, environmental and other related issues and will have gained a good all-round insight into fire safety, however it is important to remember that fire safety, at its most basic, is based upon the principle of keeping fuel sources and ignition sources separate. As in other areas of health and safety in the workplace we must set out to control the risk we are exposed to, in this and the following sections we will work through the moral, financial, and legal benefits and requirements of good fire safety management. When researching and indeed implementing fire safety management there are great similarities with other health and safety disciplines, in particular fire risk assessment, and in using similar techniques and methods of assessment it remains that elimination of the risk would always be the ultimate safety goal. However, due to the very nature and type of processes in the workplace we will always be exposed to some degree of risk, the obligation then is to manage any fire risk. The control and management of the fire risk should always be appropriate and arrived at by correct assessment, using appropriate fire risk analysis. It can be easy to fall into the trap of incorrect hazard perception for example a person with no insight or knowledge of safety systems and controls could assume that the explosives industry is "too dangerous to work in" because of the nature of the product but working in an office presents no fire risk because there are no hazards present.

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The reality of course is that because of the hazards of explosives, strict and in-depth fire management systems will (should) be in place, creating a safely managed work environment, whereas an office with no or inappropriate fire management could provide an unsafe working environment. Consider that an explosives factory will have safe systems of working and automatic fire systems, then consider an office with dated electrics, poor housekeeping and, if any, fire exits which are then locked. E1.1: Moral and financial reasons for managing fire safety Assessment criteria: E1.1 Discuss the moral, financial, and legal reasons for managing health and safety in the workplace. Moral expectations of good standards of fire safety In 2020, the UK Fire and Rescue services attended 549,913 incidents, of which 156,128 were fires and over 230,000 fire-related false alarms. Sadly, there were 289 fire-related deaths. In the US, the U.S. Fire Administration (USFA) reported 1,318,500 fires in 2018. Sadly, there were 3655 fire-related deaths. The catastrophic Australian bushfires in 2019/20 destroyed over 5,900 buildings and sadly resulted in the deaths of at least 34 people. Fires can also result in a great deal of suffering for all those affected and result in low morale within the workforce. It is also a legal requirement in many countries to prevent fire and to protect employees and other relevant persons from the effects of fire and to mitigate the effects of fire from anyone in the vicinity of a premises on fire. The financial cost of incidents (including penalties that could be imposed in the event of a false alarm) Fire can result in massive financial and economic loss involving the loss of personal property and private dwellings. The potential for material damage and loss of revenue to a small business or even a large corporation is great enough to cause that business to cease trading with the subsequent loss of jobs. Such a situation can have a massive effect on the local economy, therefore the financial effect of fire can be far reaching and is not only limited to any material damage caused at the time of any incident. It is virtually impossible to place an exact figure as to the financial cost of fire, but reliable estimates show a huge cost to society each year in both financial and human terms. In 2008 it was estimated that fires cost the UK economy over £8 billion. The U.S. Fire Administration (USFA) estimated the cost of the reported 1,318,500 fires in 2018 to be $25.6 billion. There is generally no specific “fire damage insurance policy” that can be taken out. There are however several types of policy that would pay for repair for items in the event of fire. For example, homeowner buildings and contents, business owner buildings and stock. However, the policies are likely to be expensive and will not protect against business losses such as downtime/production losses, loss of revenue or loss of customers. These uninsurable losses in the event of a fire are likely to be much greater than the insured losses.

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The Association of British Insurers (ABI) stated that fire was one of the most expensive insurance claims. In 2018 £1.3 billion was paid out to policy holders. The costs associated with the Deepwater Horizon fire and explosion in the Gulf of Mexico in 2010 were estimated at $65 billion, with over $6 billion of this estimated to be insured losses. It can be an advantage, when reporting to shareholders, to express Fire Safety Management as a business objective, much in the way of continuous improvement and similar objectives. Fire Safety Management (and other health and safety disciplines) expressed in such terms can then be budgeted for and seen as an aspect of company profit and loss. Financial Implications of false alarms A false alarm can be defined as an event in which the fire and rescue services believes they are called to a reportable fire and then find there is no such incident. False alarms bring financial implications, with possible penalties being imposed upon the organisation by the attending fire and rescue service, if they are activating frequently and falsely. The business interruption of the organisation can result in loss of production, trade, missed deadlines and therefore penalties being implemented. This may lead to an increase of pressure upon the employees to work harder and faster which could result in an increased risk of accidents occurring. False alarms may be a result of a deliberate and false nature and can result in the person (if identified) having legal action taken against them which may result in a fine being imposed, or even a custodial sentence. Attending false alarms costs fire services millions of pounds every year and understandably every brigade wants its fire fighters to be available to attend genuine emergencies rather than numerous false alarms which are not only wasteful on the resources of fire brigades, but also cause disruption and financial losses to business due to unexpected evacuations.

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Another major concern is complacency amongst occupants of premises that suffer from high rates of false alarms. People will begin to ignore an alarm when it falsely activates on a regular basis which could have devastating consequences in a real fire situation. Often false alarms are caused by owners not fully understanding how their fire alarm works or poor maintenance of the alarm system itself. Fire and rescue services have issued the following advice to building owners on reducing the number of false alarms: Ensure your fire risk assessment is up to date. Your fire alarm and detection system should be properly designed, installed, and maintained. A reputable company should be appointed to maintain your fire alarm system. Fire alarm procedures should include a designated person (or people) to confirm whether a fire is genuine. Record details of false alarms in a fire alarm logbook and undertake steps to ensure that mistakes are not repeated.

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E1.2: The role of national governments and international bodies in developing frameworks for the regulation of fire safety Assessment criteria: E1.2: Summarise how fire safety is regulated and the roles of national government and international bodies. Employers’ responsibilities All employers have a responsibility towards the employees and visitors who may work at or visit their premises. They have a duty to protect the health, safety and welfare of their employees and other people, who might be affected by their business. They must do whatever is reasonably practicable to achieve this. To enable them to fulfil their duties, and comply with any safety laws, risk assessment and fire risk assessments will be required to be carried out. These will address all risks that may cause harm in the workplace to its occupants. Information regarding any risks, and how protection is enabled, should be submitted along with any relevant instructions or training. Workers’ responsibilities Workers will also have responsibilities to themselves, other workers, and visitors in the workplace. Everyone is entitled to work in environments where risks to their health and safety are properly controlled. Under national health and safety law, the primary responsibility for this is usually that of the employer. Workers have a duty to take care of their own health and safety and that of others who may be affected by their actions at work. All workers should, additionally, cooperate with employers (for example, follow rules and procedures) to assist everyone in meeting their legal requirements. The role of enforcement agencies and other external agencies including consequences for non- compliance. Addressing Fire Safety Management at a National Level Across the world, National Governments have taken a varied approach in addressing Fire Safety Management and many have delegated the power to both create and regulate below their immediate control, so that only in times of reflection and reparation following a major, and or severe fire incident can Government intervene. There are a multitude of reasons why fire safety is managed differently on a National level, and in many cases the level of development in a nation's fire safety legislation is intrinsically linked to its health and safety legislation and regulation. Another reason is the overall development level of the country in terms of industry where fire safety and prevention equipment has become a necessary requirement to ensure personal safety during processing of materials into goods. Therefore, in a country with little industrial industry and more farming industry, fire regulation may be of a more basic nature and less technical overall. Countries with a high degree of foreign investment or industry on home soil may also be made more aware of higher levels of fire safety perceived as being required by the incoming nation or likewise by the host country. This requires a greater level of risk management in relation to fire safety of the organisations' operations.

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Countries who have suffered a high level of severe fatality incidents through fire events or those with naturally occurring fires, such as the forest fires of Australia, are often the leaders of fire protection, prevention and management through necessity, and on a smaller scale, those organisations or nations who have suffered great human loss or industrial disaster due to fire breakout are the first to look at the lessons learned from the event, and put in place new legislation to ensure that a repeat of the incident cannot happen ever again. In this way, Fire Safety Management has evolved and still evolves in a multitude of ways every day throughout the world, and the learning process will never end. International Bodies and the part they play in Standardisation On an International level, managing fire safety is an extremely complex business as most nations manage their fire legislation at local level, for example, in the US each of its 52 states creates and directs their own legislation, and fire safety standards don't come from Washington DC, but in the main from the American National Standards Institute (ANSI), which coordinates American standards across other nations globally. The US is also seen as being the world leader in fire protection systems. Likewise, in the UK, although legislation comes from Government, the way the law is enforced differs slightly across each individual Fire Authority, which means not all legislation is managed consistently and it is open to local interpretation. This works until the outcome of a fire is severe, in which case the local interpretation is often looked at in the court process and can result in Fire Authorities being prosecuted due to poor judgement and management of the legislative requirements. In other parts of the world, namely Europe that has over 40 individual countries, there is specific regulation within each country that has no bearing on member countries at all. However, European standardisation does exist in part, led by the International Standards Organization (ISO), and these encompass such as the British Standards (BS), the Spanish Asociación Española de Normalización y Certificación (AENOR), and German Deutsches Intitut fur Normung (DIN). The ISO brings together over 150 countries and their respective legislation, standards, products, and services (in a similar way to the American model), and the combined result is often legislation that goes beyond that of each individual member country. Recent years have seen European led initiatives, with support from the European Commission and the EU becoming accepted as excellent fire safety practice and, as such, have begun to be taken seriously and not seen as conflicting with existing compliance requirements. One very visible initiative was the European classification system for fire extinguishers for all European countries, to avoid confusion for those organisations and civilians who visit and trade in more than one European country. Australia is seen as a world leader in terms of Fire Safety and together with New Zealand. Australia has the most extensive legislation and standards for fire safety, protection, and systems installation. Asia is in the main led by Japan, with China and other countries such as the Philippines beginning to make huge and positive changes to their fire safety management practices following events of fire occurring. Japan however leads the field regarding fire safety regulations. In terms of other parts of the world such as Africa, which is largely seen as being a continent of developing countries, fire safety is managed very differently between each individual country, such as the Republic of South Africa having

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addressed the need for fire legislation and other countries having a basic level of legislation, or simply nothing in place at all. This makes international trade a complicated affair where an organisation that is trading, should in all good conscience adopt the highest level of fire safety management it can, for its employees, clients and for its own corporate reputation and international standing. Therefore, the role of International Bodies in formulating frameworks for the regulation of fire safety is critical to the safety and lives of millions of people and a very important role to undertake wisely. International Organisation for Standardisation (ISO) The ISO was founded in 1947 in London when delegates from 25 countries met to create an International Organisation to: • 'Facilitate the International coordination and unification of industrial standards'. Today, ISO is the world's largest developer of voluntary International Standards with members from 163 countries. What are International Standards? International Standards give specifications for products, services, and good practice, helping to make industry more efficient and effective. ISO standards cover most aspects of technology and business. These have been developed through global consensus, and they help to break down international trade barriers. The most popular ISO standards include: • ISO 9000: Quality Management • ISO 14000: Environmental Management • ISO 45001: Occupational Safety and Health Management Fire standards include: • ISO 14934 – 2: Fire tests Calibration and use of heat flux meters Part 2: Primary calibration methods • ISO 7240 – 23: Fire detection and alarm systems Part 23: Visual alarm devices

External agencies Fire Authorities

Responsibilities of a fire authority might include, but are not limited to: • Promoting fire safety in its area of responsibility. This might include:

o Providing information and publicity on how to prevent fire o Giving advice on how to restrict fire spread in buildings • Giving advice on means of escape from buildings in the event of fire • Extinguishing fire in its area • Protecting life and property in the event of fire in its area • Ensuring it has enough resources to meet all normal requirements • Providing training for its personnel • Making suitable arrangements for dealing with calls for help and summoning personnel

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In the UK these are specific requirements of the Fire and Rescue Services Act 2004. In addition, Fire Authorities may be given enforcement powers (as is the case in the UK). Local Authorities Local authorities can have a significant role to play with regards fire safety.

In the UK, the government has produced a series of documents about meeting the requirements of the Building Regulations for England. The Regulations contain details of what is required to meet fire safety standards. The Local authority has a general duty to enforce the building regulations in its area. It will seek to do so by informal means, such as offering advice on the required corrective actions. If informal enforcement does not achieve compliance with the regulations, the local authority has formal enforcement powers, which it may use in appropriate cases. These powers include issuing notices, imposing fines, or instituting prosecution proceedings. Insurance Companies Insurance companies style the cost of policies based on risk models or on the assessment of a property if no such model exists. Typically, a domestic property will fall into a certain category type and with only limited variables the level of fire risk (and your cost) can be calculated. In a commercial property, however, the variables can be wide ranging and therefore an insurance assessor may be used to determine the level of fire risk. The insurance provider will have access to a large database of information and in fact the insurance company may have ' new ' information and recommendations prior to the governmental bodies. It is in the business interest of the insurance company to assist you in the reduction of fire risks, and the recommendations and requests as an outcome of an insurance audit can often be integrated into your own fire risk assessments and control methods. National Fire Protection Association (NFPA) The US National Fire Protection Association (NFPA) is an international non-profit organization that was established in 1896. The company's mission is to reduce the worldwide burden of fire and other hazards on the quality of life, by providing and advocating consensus codes, standards, research, training, and education. With a membership that included more than 70,000 individuals, from nearly 100 nations, NFPA is the world's leading advocate of fire prevention, and an authoritative source on public safety. Codes and Standards NFPA is responsible for 300 codes and standards, that are designed to minimise the risk and effects of fire, by establishing criteria for building, processing, design, service, and installation in the United States as well as many other countries. Its more than 200 technical codes and standard development committees are comprised of over 6,000 volunteer seats. Volunteers vote on proposals and revisions in a process that is accredited by the American National Standards Institute (ANSI). National Fire Codes Subscription Services, All Access provides individual subscribers with online access to every NFPA code and standard, Handbooks and Annotated Editions. In addition, NFPA provides free online access to its codes and standards.

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The most commonly used codes are: NFPA 1. Fire Code: Provides requirements to establish a reasonable level of fire safety, and property protection in new and existing buildings. NFPA 54. National Fuel Gas Code: The safety benchmark for fuel gas installations. NFPA 70. National Electric Code: The world's most widely used and accepted code for electrical installations. NFPA 101. Life Safety Code: Establishes minimum requirements for new and existing buildings, to protect building occupants from fire, smoke, and toxic fumes. The role of enforcement agencies Law enforcement agencies may be defined as: “ A body sanctioned by local, state, or national government to enforce laws and apprehend those who break them ”. The best example on a global basis is perhaps the police, whose role is to prevent crime and apprehend those who break the law. In terms of fire safety, the purpose is very much the same – to prevent breaches of fire legislation and to act on those who break fire laws. Again, enforcement varies around the world with a mixture of national, federal, and state enforcement being applied. In the UK, a national approach is used with local fire authorities enforcing fire legislation in their areas of responsibility. The powers granted to inspectors in England and Wales, under the Regulatory Reform (Fire Safety) Order 2005 (RRFSO), include: (a) to enter any premises which they have reason to believe is necessary for them to enter for the purpose mentioned above, and to inspect the whole or part of the premises and anything in them, where such entry and inspection may be effected without the use of force. (b) to make such inquiry as may be necessary for any of the following purposes— (i) to ascertain, regarding any premises, whether the provisions of this Order or any regulations made under it apply or have been complied with. (ii) to identify the responsible person in relation to the premises. (c) to require the production of, or where the information is recorded in computerised form, the furnishing of extracts from any records (including plans)— (i) which are required to be kept by virtue of any provision of this order or regulations made under it. (ii)which it is necessary for them to see for the purposes of an examination or inspection under this article, and to inspect and take copies of, or of any entry in, the records. (d) to require any person having responsibilities in relation to any premises (whether or not the responsible person) to give them such facilities and assistance with respect to any matters or things to which the responsibilities of that

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person extend as are necessary for the purpose of enabling the inspector to exercise any of the powers conferred on him by this article. (e) to take samples of any articles or substances found in any premises which they have the power to enter for the purpose of ascertaining their fire resistance or flammability. (f) in the case of any article or substance found in any premises which they have the power to enter, being an article or substance, which appears to them to have caused or to be likely to cause danger to the safety of relevant persons, to cause it to be dismantled or subjected to any process or test (but not so as to damage or destroy it unless this is, in the circumstances, necessary). Enforcement In the event of an inspector finding a fire related problem, the following enforcement options under them are available: • Alterations notice • Enforcement notice • Prohibition notice The conditions required for serving the notices are : Alterations Notices If the premises: a. Constitute a serious risk to relevant persons (whether due to the features of the premises, their use, any hazard present, or any other circumstances). b. May constitute a risk if a change is made to them or the use to which they are put. An alterations notice must: a. State that the enforcing authority is of the opinion referred to in paragraph (1). b. Specify the matters which in their opinion, constitute a risk to relevant persons or may constitute such a risk if a change is made to the premises or the use to which they are put. Where an alterations notice has been served in respect of premises the responsible person must, before making any changes which may result in a significant increase in risk, notify the enforcing authority of the proposed changes. Enforcement notice If the enforcing authority is of the opinion that the responsible person or any other person has failed to comply with any provision of the RRFSO or of any regulations made under it. Prohibition Notices If the enforcing authority is of the opinion that use of premises involves or will involve a risk to relevant persons so serious that the use of the premises ought to be prohibited or restricted.

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Prohibition and improvement notices are subject to the right of appeal. In each case, contravention is an offence and is one of the few offences under appropriate Acts which have penalties of imprisonment in addition to or instead of a fine. Being issued with any of the above notices is not in itself, an offence. However, non-compliance with a notice will become an offence. Prosecution In some cases, the inspector may consider that it is also necessary to initiate a prosecution for failing to comply with fire safety law. There are two categories of offence in which a business may be faced with prosecution. Summary offences: A summary offence is a criminal offence that is tried summarily, in other words, in front of a magistrate. Indictable offence: An indictable offence is a serious criminal offence that requires trial by jury in a Crown Court. Note that the above inspection and enforcement powers apply to the UK and may differ in other parts of the world. Refer to specific national, federal, or state legislation for details in any specific country.

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NEBOSH Certificate in Fire Safety

Element E2: Principles of fire and explosion E2.1 The principles of combustion, fire growth and fire spread Assessment criteria E2.1-E2.3: Describe the principles of combustion in relation to fire safety. The fire triangle

The fire triangle is a simplistic graphic representation for understanding the components necessary for most fires, and whilst the fire triangle model remains valid, in the last few years it has started to be replaced by the Fire Tetrahedron, which provides a more complete model. In addition to the triangle model, the tetrahedron is also described below. The fire triangle illustrates the rule that in order to ignite and burn, a fire requires three elements, heat, fuel, and oxygen. The fire is prevented or extinguished by removing any one of them. Combustion occurs when the three elements are combined in the right mixture.

As part of the fire triangle, fuel is needed for a fire to burn. Until a fire runs out of fuel, it will continue to burn. The fuel can be physically or chemically removed from a fire. An example of physical removal includes removing logs from a campfire using tools such as tongs or a shovel. In the case of a larger fire, such as a wildfire, constructing a fuel break by physically removing or altering vegetation, grass, or shrubs, will ‘remove’ the fuel from the fire. Chemical removal involves interrupting the combustion process by either

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suppressing the flames or altering the chemical reactions that sustain the fire. For example, the application of a dry chemical fire extinguisher.

Without enough heat, a fire cannot begin or continue. Heat can be removed by applying water, where the heat turns to steam, taking the heat with it. It should be noted that the application of water can cause some types of fire to spread. For example, applying water to hot oil or fat fires. Turning off the electricity in the event of an electrically related fire removes the heat source, although fuels that are still burning may continue to burn.

Oxygen can be removed from a fire by smothering the fire with an extinguishing agent, such as carbon dioxide, or covering a chip pan fire with a fire blanket. The fire triangle remains an effective teaching tool but does not demonstrate the fourth element of fire, the sustaining chemical reaction. This has led to the development of the fire tetrahedron. In most circumstances, the fire will fail to ignite, or is extinguished, depending on which element is removed. There are certain chemical fires where knowledge of the fire tetrahedron is essential. The following diagram is a two-dimensional representation of the tetrahedron, it is useful to visualise the fire tetrahedron as a pyramid, having four sides including the bottom.

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Combustion is the chemical chain reaction that feeds a fire more heat and allows it to continue. With most types of fires, the old fire triangle model works well enough, but when the fire involves burning metals, such as magnesium and lithium, it becomes useful to consider the chemistry of combustion. Putting water on such a fire could increase the heat of the fire and could be the catalyst for an explosion. In this type of fire, specialised chemicals must be used to break the chain reaction of metallic combustion, therefore extinguishing the fire. Complete combustion reactions need a plentiful supply of air so that the elements in the fuel react fully with oxygen. Fuels such as natural gas and petrol contain hydrocarbons. These are compounds of hydrogen and carbon only. Incomplete combustion reactions occur when the supply of air or oxygen is poor. Water is still produced, but carbon monoxide and carbon are produced instead of carbon dioxide. Combustion Combustion is a chemical reaction that occurs between a fuel and an oxidiser, typically in the form of oxygen gas (O 2 ). It is a rapid exothermic (heat-releasing) reaction that produces flames, heat, and light. Combustion is an essential process in many everyday applications, such as burning fuels for heating, cooking, and transportation. Note that in addition to oxygen (O 2 ), chemicals such as hydrogen peroxide (H 2 O 2 ), nitric acid (HNO 3 ) and potassium nitrate (KNO 3 ) are typical oxidising agents. The combustion reaction involving nitric acid is highly exothermic, and can be represented as follows: 4 HNO 3 + 5 O 2 → 4 NO 2 (nitrogen dioxide) + 6 H 2 O 2 During combustion, the fuel undergoes oxidation, where it reacts with oxygen to produce energy in the form of heat and light. The fuel and oxygen molecules break apart, rearrange, and form new molecules. The reaction products of combustion typically include carbon dioxide (CO 2 ), water vapour (H 2 O), and other combustion byproducts such as carbon monoxide (CO), nitrogen oxides (NO X ), and particulate matter. The reaction can be represented by a chemical equation, where a typical hydrocarbon fuel like methane (CH 4 ) reacts with oxygen: CH 4 (methane) + 2 O 2 (oxygen) -> CO 2 (carbon dioxide) + 2 H 2 O (water vapour) + energy The release of energy in the form of heat and light is what makes combustion useful for various applications. The energy generated during combustion can be harnessed for heating, electricity generation,

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and powering engines. However, it is important to note that combustion can also release pollutants and contribute to environmental issues such as air pollution and climate change when not properly controlled or when dirty fuels are burned. Whilst the combustion requires an ignition source to initiate the chemical reaction between the fuel and oxygen, if the fuel and oxygen are present, the combustion process becomes self-sustaining. Combustion reactions can be complete or incomplete.

Complete combustion A complete combustion reaction occurs when a fuel combines with oxygen (O 2 ) in the presence of a flame or sufficient heat. This reaction results in the formation of carbon dioxide (CO 2 ) and water (H 2 O) as the primary products. Here is an example of the complete combustion of methane (CH 4 ):

CH 4 + 2 O 2 → CO 2 + 2 H 2 O Incomplete combustion

Incomplete combustion occurs when there is insufficient oxygen during the burning process. As a result, the fuel does not completely react with oxygen, leading to the formation of products other than carbon dioxide and water. Incomplete combustion usually produces carbon monoxide (CO) and water (H 2 O), along with other byproducts such as carbon (C) or soot. Here is an example of incomplete combustion of methane: 2 CH 4 + 3 O 2 → 2 CO + 4 H 2 O In this case, carbon monoxide (CO) is formed instead of carbon dioxide (CO 2 ) due to the limited availability of oxygen. Methods of heat transfer Fire and smoke can easily and quickly spread through buildings and neighbouring properties if it is not quickly controlled. The spread of fire is reliant upon the following methods:

• Conduction. • Convection. • Radiation. • Direct Burning.

Conduction This can occur in solids, liquids, or gases, although it is more common in solids. Thermal conductivity, the ability to conduct heat, varies between materials. Most metals conduct heat relatively easily and are classed as good conductors. Steel conducts heat very well. A steel girder passing through a structure may conduct enough heat through to a connecting room, thus spreading the fire to other rooms.

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Convection This only occurs in liquids and gases, including smoke.

A good example is the process of convection when a pan of water is heated. A pan full of water is heated from the base of the pan and the water warms up, it expands and therefore becomes less dense and so a given volume is lighter. Because the heated liquid is buoyant, it rises, then colder, denser fluid takes its place at the bottom, this then becomes heated and so a circulation is set up. Updraft in chimneys is caused by convection and by the same principle when a fire occurs in a building. Convection currents can convey hot gases produced upwards through stairwells, open lifts, and service shafts, thereby spreading the fire to the upper parts of buildings. If the hot gas products escape from the upper levels, cool air must enter at low levels to replace them. This will help to maintain the burning as a fresh supply of oxygen will be drawn into supply the fire. Radiation Heat is transmitted by a means, which is neither conduction nor convection nor requires an intervening medium. An everyday example of this is a radiant heater. When placed at a high level in a room the heat can be felt at lower levels, where neither conduction nor convection can carry it. This method of heat transmission is called radiation and does not involve any contact between the bodies that are providing and accepting the heat. For all intents and purposes, it behaves in the same way as light (‘visible radiation’). Light travels in straight lines and will be transmitted through some materials and not others. When radiant energy (heat in this context) falls upon any material, there are 3 potential outcomes: • Transmission. Many fires have been caused by radiation. One of the most common is clothing being ignited by being placed too close to a source of radiation, as sometimes happens when people air clothes placed too close to a fire. Radiant heat from the sun passing through a glass window has sometimes acted as a lens, having been concentrated by an object inside the house, such as a magnifying glass or a shaving mirror. Direct burning One of the main methods of fire spread is by physical flame contact. As a material burns, it has the potential for the flames from the combustion process to touch and ignite other materials nearby. • Absorption. • Reflection.

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Heat transmission routes This simplified diagram shows the heat transmission routes of convection, radiation and conduction through a wall or barrier. The cold air contains enough 'fresh ' oxygen to support and increase combustion. The stages of fire

There are certain stages of a fire which can fall into the following five categories: Induction The induction stage is the precursor to ignition where preheating, distillation and slow pyrolysis are in

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progress. Minute gas particles are generated and transported away from the source by diffusion, air movement, and weak convection movement. Ignition The point of ignition is reached when the reaction becomes self-sustaining and does not require an external heat source. Growth (smoulder and flame) The smouldering stage is a region of fully developed pyrolysis that begins with ignition and includes the initial stage of combustion. Invisible aerosol and visible smoke particles are generated and transported away from the source by moderate convection patterns and background air movement. The flaming stage is a region of rapid reaction that covers the period of initial occurrence of flame to a fully developed fire. Heat transfer from the fire occurs predominantly from radiation and convection from the flame. Steady state The steady state, also called the free-burning phase, is generally when enough oxygen and fuel are available for fire growth, and open burning to a point where total involvement is possible. Whilst sufficient fuel and oxygen are present, this stage will continue. Decay In this (final) stage the combustion is coming to an end, the fire is reducing in heat in a constant manner, and ‘the fire is burning itself out’ . The decay stage does eventually occur naturally, however, fighting a fire is about getting to the decay stage as quickly as possible. It is also useful to be aware of the steady state phase. This is the phase when by various means or methods, the fire is coming under control and is characterised by a heat release rate, which is relatively unchanging. Transition from the growth phase to the steady state phase can occur when fuel or oxygen begins to be limited, or when suppression activity begins to impact the fire. Factors that influence fire growth rates and smoke movement Most fires start out quite small and because of the circumstances can spread and very quickly get out of control. Fire growth is influenced by the amount of oxygen in the atmosphere. A well-ventilated room will quickly cause a fire to grow at a very rapid rate. Oxygen-enriched atmospheres considerably increase the risk of fire and fire growth rates. Normally harmless sparks or materials which do not burn in the air, including fireproof material, can burn vigorously in this type of oxygen-rich environment. Oil and grease are particularly hazardous in the presence of oxygen as they can ignite spontaneously and burn with explosive violence. They should never be used to lubricate oxygen or enriched air equipment (special lubricants which are inert when used with oxygen should always be used).

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Cigarette lighting in the presence of oxygen-enriched atmospheres, such as one created by using oxy- acetylene welding and cutting equipment can cause many accidents. It is therefore impossible to over- emphasise the danger of smoking in oxygen-enriched atmospheres, or where oxygen enrichment can occur. In such areas, smoking must be forbidden and consideration given to prohibiting the carrying of smoking materials. The second factor is the speed at which flammable vapours are released from the fuels present. This will depend on the type of material, its size and the temperature it is being exposed to. Some materials, such as flammable liquids will readily give off vapours, and will significantly increase the amount of vapours given off as the temperature is raised by a small amount. Other materials, such as a large block of wood, may not readily give off vapours until exposed to particularly high temperatures. The size of the flammable material is significant, in that if it is small and finely divided, such as a dust or droplet of fuel, the rate of vapour being evolved and fire growth will be very rapid and may resemble an explosion.

The fire growth rate is mainly affected by the rate of production of flammable fuel in the form of vapours, and the availability of oxygen, but the following can also have an influence: • Smoke Movement. • Building Construction. • Ventilation. • Contents. Smoke movement This will be dictated by the temperature of the smoke. Cold smoke will spread laterally, possibly at a low level, presenting a principal hazard of reduced visibility, whereas hot smoke is more hazardous since it is a fuel above its ignition temperature and will spontaneously combust when it reaches available oxygen.

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Hot smoke can be carried with the convection currents produced by the combustion process of the fire and will spread laterally across the ceiling, then upwards at every opportunity. Due to the buoyant nature of hot smoke, it can travel a considerable distance from the seat of the fire. The fire gases which are mixed in with the smoke, are both flammable and toxic. The majority of smoke will contain carbon monoxide (proportional to the available oxygen) along with other toxins, such as hydrochloric acid from the combustion of electrical conductor insulation, and compounds of cyanide from the combustion of synthetic upholstery foam infill. Such gases will quickly render people unconscious and cause death, this helps to explain why people who die from fires that occur whilst they are asleep tend not to attempt to escape. The effect of construction Depending on the design of the building will influence the rate of fire growth and the movement of smoke. The style and method of construction can play a major part in fire growth, as can the maintenance of structural elements. Large open-plan and open-floor buildings do very little to limit the free air that can feed a growing fire and flashover is a real possibility. It is important to check the construction of a building to see what easy paths are available for smoke and fire, to circulate around the building: It is important to check the construction of a building to see what easy paths are available for smoke and fire to circulate around the building: • Vertical shafts such as lifts and ducts. • Open stairways. • False ceilings. • Voids behind wall panelling. • Doors, which are ill-fitting, damaged or wedged open. • Cavities. Any holes in fire-resistant structures should be 'fire stopped' , to maintain the integrity of the construction. The materials used in the construction are also vital to the growth of the fire within the building. If the construction materials are non-combustible, the fire will only grow because of the contents of the building. Combustible building boards are often used as internal linings to walls and ceilings, but the fire growth rate of these materials can be reduced by treatment with fire-retardant paints. Therefore, to provide fire protection around internal timber doors, intumescent strips can be fitted at the edge of the door or frame. This will seal the gap in the event of a fire and can achieve 30 minutes of fire protection. Cavities are concealed spaces enclosed by the elements of a building (including a suspended ceiling) or contained within a building element. Sealing cavities can create difficulties, especially where construction techniques rely on through ventilation of the cavity. Cavity barriers can be put in place to restrict the penetration of fire and smoke to restrict the movement within the cavity. Barriers can be provided at the edges of cavities, including around openings. Cavity barriers can also be provided at the junction between an external cavity wall and a compartment wall that separates buildings. Insulated core panels Many buildings have insulated core panels as exterior cladding, or for internal structures and partitions. The simple construction of these panels enables alterations and additional internal partitions to be erected with minimum disruption to the business. They normally consist of a central insulated core, sandwiched between an inner and outer metal skin. There is no air gap. The external surface is then normally coated with a PVC

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covering to improve weather resistance or the aesthetic appeal of the panel. The central core can be made of various insulating materials, ranging from virtually non-combustible through to highly combustible. However, problems can arise from having panels in place, such as the provision of hidden fire spread within the panels and the production of black toxic smoke. Fire spread could also lead to a flashover. Construction materials The materials used within the building will influence the speed and outcome of fire growth and fire spread. Some materials will have a good fire resistance level, and others will be highly combustible. Typical materials include: • Bricks are widely used in the construction of buildings and offer a good fire resistance level. • Concrete. This has good fire resistance and is more effective when used in block form. • Timber is combustible, but its resistance can be improved by treating it with fire retardant products. • Paints are used quite frequently on walls, ceilings, and other surfaces to slow the spread of fire. Flame-retardant and intumescent paints have been successfully manufactured which can now be applied to most surfaces. • Plastering is widely used on internal walls, and if the plaster consists of lathing or expanded metal, it can have a strong fire resistance level. • Plastics should be treated with fire retardants or protected in other ways. Failure to do this can aid in the spread of fire and the production of smoke. Internal linings Fire spread can be affected by the internal linings of the building, especially along the escape route. Internal linings of the building, such as walls, ceilings and partitions should be treated with a lining material which will restrict flame spread. The effect of ventilation Ventilation is the key factor in fire growth. If a fire has unlimited ventilation or air supply, then a flashover can easily occur. Ventilation systems will contribute to fire spread in two ways. Firstly, a ventilation system can provide a supply of fresh air (oxygen) to feed a fire and secondly, smoke (which is a fuel) can cause fire to spread through ventilation systems to other parts of the building, and bypass fire and smoke-resistant structures. The effects of contents During a fire, the contents of a building have an obvious effect on the rate of growth, and it is easy to imagine the dangers of a warehouse or enclosure containing (highly) flammable substances. However, it is well-publicised how rapid the rate of fire growth can be in a domestic house fire. Domestic fires, almost by definition, will influence items of furniture. The classic scenario of this is the materials of a sofa which when ignited can generate substantial heat (and smoke), due to the three methods of transmission, then ignite other items rapidly and increase the growth of fire throughout the building. A UK HSE guidance document HSG 64 ’Assessment of Fire Hazards from Solid Materials’ (now withdrawn) gave the following as examples of materials which were categorised as ‘high-risk’ and therefore present a great danger: • Acrylic fibre. • Acrylic mixture.

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• Acrylic over locks. • Expanded polystyrene. • Flexible polyether (polyurethane foam). • Polypropylene silver. • Rigid polyurethane foam (low density). Other considerations include the type, quantity, distribution, and reactive nature of the materials stored. The conditions required for, mechanisms of, and impacts of flashover and backdraught Open burning fires and fire in a physical enclosure, defined in literal and simplistic examples are something akin to a bonfire and that of a fireplace, i.e. one is contained the other not. Whilst maintaining the basic principles of containment we also need to understand more sophisticated and larger scale examples. In the construction of a building, rooms or areas could be constructed using fire-retaining materials thus creating a physical fire enclosure, which will inhibit the spread or growth of fire. The obvious opposite is open areas or rooms not constructed from suitable materials, which have little if any effect upon the containment of fire growth. Consider fire growth in a domestic house fire and compare a room with a closed door to an open area such as a staircase. Open burning fires and physically enclosed fires In an open burning fire outside a building, such as a bonfire, the hot gases of combustion rise into the atmosphere with very little effect on the temperature of the materials involved in the fire. As a result, the speed of fire growth is generally much slower than it would be in an enclosed space. Most people will be familiar with a fire outdoors, which people can move back from as it grows. If the wind is blowing the smoke towards them, they can move right away from the fire to a place of safety because they have a choice of escape routes not affected by heat or smoke. A fire in a physical enclosure A fire in an enclosed room is however a very different phenomenon to an open burning fire. The speed of fire growth can be devastating, with two fire phenomena of specific note: • Flashover. • Backdraught. Flashover A flashover can occur when a fire is free-burning in a room. For this to happen there must be a good supply of air, either from the large dimensions of the room, an open door, an open window or a ventilation system. As the item that was initially ignited burns and the fire grows, the radiated heat heats up all the other materials in the room until they reach their spontaneous ignition temperature. Items in the room will then instantly ignite, creating the impression that the fire has flashed from one side of the room to the other. Although this phenomenon is very serious, it is not the most dangerous, as it is obvious that there is a severe fire in progress.

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