Fire Safety Management Past Paper PDF

School of Architecture & the Built Environment **Fire Safety Management BE6810** **1.0 [FIRE CHEMISTRY]** **Learning Outcomes** **At the end of this lesson, learners will be able to:** - **Explain the triangle of combustion.** - **Describe the stages of combustion.** - **Identify fuel s...

School of Architecture & the Built Environment **Fire Safety Management BE6810** **1.0 [FIRE CHEMISTRY]** **Learning Outcomes** **At the end of this lesson, learners will be able to:** - **Explain the triangle of combustion.** - **Describe the stages of combustion.** - **Identify fuel sources.** - **Differentiate between ignition and combustion.** - **Identify the products of combustion.** - **Explain the effect of heat on material properties.** - **Identify the classes of fire.** - **Differentiate fire from explosion.** 1. **Definition** **Fire** -- a chemical reaction brought about by the combining of fuel and oxygen and the application of sufficient heat to cause ignition. **Combustion --** a chemical reaction that feeds a fire more heat and allows it to continue. In summary, ignition is **[the beginning of a fire]** and combustion is **[the continuation of a fire]**. **1.2 The Standard Fire Triangle** The fire triangle is a representation of the three components necessary for a fire to start and once started to continue to burn. They are: 1. Fuel - any kind of combustible material (in solid, liquid or gas form). 2. Oxygen - to sustain the combustion. 3. Applied heat - **[any kind of combustible material (can be in solid, liquid or gas form).]** Without any one of the above components, fire will not start. Once a fire starts, a fourth component, **[combustion heat],** which is the heat generated by the reaction must be taken into consideration. This fourth component becomes significant when considering methods of extinguishing fire. Once combustion is in progress, removal of **[one component]** will cause the fire to be extinguished. In fires involving buildings, the most common component selected is the removal of **[heat],** (i.e. by pouring large quantities of water onto the fire and its surrounding to remove both the applied and combustion heat). The advantage of using water is, it is low cost and plentiful supply but the disadvantage is water in itself can also cause considerable damage. **[Fuel Characterisation] (see Fig. 2)** **There are different types of fuels: solids, liquids, and gases. All materials e.g. solid, liquid, gas will burn when sufficient heat is applied. It is the vapor that burns, not the material.** **Some important concepts are:** - **The flashpoint is the temperature in which a material (solid/ fuel) that gives off sufficient vapor to flash across the surface temporarily.** - **The fire point is the temperature in which heat from the combustion process is sufficient to cause the material (solid/ liquid) to give off more vapor that sustain the combustion chain reaction.** - **The melting point is the temperature in which the solid material melts.** - **The boiling point is the temperature in which the liquid material boils.** - **The vapor pressure is the pressure of the vapor acting on the container wall.** - **The vapor density is the density of a gas in relation to an equal volume of air.** - **The flammability range (FR)** **refers to the concentration range of a flammable gas or vapor in air that can ignite and sustain combustion when exposed to an ignition source. It indicates the lower and upper limits of the gas or vapor concentration required for combustion to occur.** - **The FR is typically expressed in terms of percentage volume or percentage lower explosive limit (LEL) and upper flammable limit (UEL).** - **The LEL represents the minimum concentration of the gas or vapor in air below which it is too lean to burn, while the UEL represents the maximum concentration above which it is too rich to burn e.g. the flammability range of gasoline is between 1.4% -7.6%.** ***Fig. 2*** **1.2.1 Combustion of Solid Fuel** When heat is applied to a solid, its temperature will increase. Flammable vapours will also be released. These vapours will then ignite and burn to form a flame. The combustion of vapours will release heat. This heat will be transferred to the fuel resulting in the releasing of more flammable vapours to enter what is now a "**closed feedback loop**." (see Fig. 3). The source of the heat is usually an external source (e.g. flame, heat from friction, sparks, etc.). It should be noted that a thin fuel (e.g. a sheet of paper) ignites more readily than a thick fuel (e.g. a book or a plank of wood) because less heat is required to raise the temperature to the point at which fuel vapours are produced. The combustion of vapour will release more heat. This heat will be transferred to the fuel... releasing of more flammable vapour. **1.2.2 Combustion of Liquid Fuel** **[Liquid Fuel]** Liquid fuel (e.g. cooking oil) behave in a similar manner to solids. They require high heat to raise the temperature to a point where they will ignite. The ***"Flash Point"*** of a liquid is defined as "the **lowest temperature at which the liquid gives off enough vapour** to be ignited" (start burning) at the surface of the liquid. **[Combustible liquids]** have a flash point between **[38 °C and 94 °C]**. Other liquids (e.g. paraffin and white spirit) require much less heat to release sufficient vapour for ignition to occur. Note: Liquid fuels themselves do not burn. It is a mixture of vapours and air that cause them to burn. **[Flammable Liquid]** These are classified as **[flammable]** liquids and have a flash point below 38 °C and they pose a greater hazard than combustible liquids. These **flammable** liquids (e.g. petrol and ether) will produce sufficient vapour at normal temperature that can be easily ignited by a spark. (see Fig. 4) They are particularly hazardous and require special precautions to ensure that the vapour is not permitted to come into contact with a source of ignition. **1.2.3 Ignition Sources (Heat)** Common sources of heat include open flame and those caused by mechanical or electrical action. Friction between two surfaces (mechanical action) produces heat. Resistance, arching, static and lightning are electrical sources of heat. **1.2.4 Fire Extinguishment** A fire can be extinguished by: a. **Removing the Fuel** When circumstances permit, remove the unburnt solid combustible material from the fire area. For liquid and gas fuels, shut-off the pipe valves to cut off the supply. \(b) **Cooling the Burning material** Water is a common extinguishing agent. Water will cool the fuel so that it no longer releases sufficient vapour to sustain combustion. \(c) **Excluding Oxygen** Foam applied to the surface of a burning liquid acts as a physical barrier, which prevents the release of vapour into the combustion zone above the surface of the liquid. The foam will also reduce the effect of radiation from the flame onto the fuel surface. The action of carbon dioxide and other inert gases will reduce the oxygen concentration sufficiently to stop the combustion process. **1.2.5 Classification of Fire** *(Singapore Standard SS578:2019)* In order to consider the suitability of different extinguishing agents for different types of fire, fires are grouped into classes according to the nature of the fuel. ***Class A*** - Fires involving ordinary **combustible** **solids** (e.g. wood, textiles, paper, plastic, rubber). To extinguish such fires, use water, foam or dry powder fire extinguishers. ***Class B*** - Fires involving **flammable** or **combustible** **liquids** (e.g. oil, paints, thinner, liquefiable solids). To extinguish such fires, use foam or carbon dioxide fire extinguishers. ***Class C*** - Fires involving **flammable** **gas**. The proper way to extinguish Class C fire is to switch off the main gas switch. There is no classification for electrical fires under the SS578:2019) ***Class D*** - Fires involving **combustible metals** (e.g. potassium, magnesium, sodium, etc.). Use Class D fire extinguishers for such materials. ***Class F*** - Fires involving **cooking medium** (e.g. vegetable or animal oils and fats) in cooking appliances. To extinguish such fire, use wet chemical fire extinguisher or fire blankets to throw over the fire to extinguish such flames. **Note**: SS578 defines classes of fires according to the materials undergoing combustion. Hence, it **[does not define a particular class of fire involving an electrical risk. ]** **1.3 Products of Combustion** The following are the products of combustion: \(a) Thermal - Flame Damage to property due mainly to thermal effects. \(b) Non-Thermal --Smoke \- Gases The damage to property is due mainly to thermal effects although smoke and gases can also cause considerable damage. Some gases produced during combustion are corrosive or become corrosive when mixed with water. Most fire deaths or injuries, however, may be attributed to smoke or gases (more details in topic on smoke control). Heat from a fire can destroy a building. Steel begins to soften at temperature above 400°C. When steel loses its strength, it will result in a collapse of the building. Heat from a fire will also help to raise the fuel temperature, resulting in an increase in the severity of a fire. **1.4 Types of Explosion**  Explosion is a "super-fast and violent oxidation reaction" that gives off heat, smoke, light, and overpressure in much greater intensities. There are two types of explosion: physical explosion and chemical explosion. **Case Study 1** [Tuas Explosion](https://www.channelnewsasia.com/singapore/sim-card-post-paid-mobile-phone-line-scam-syndicate-arrest-3536091) An explosion in a Tuas industrial building killed three people and injure seven others in the explosion at 32E Tuas Avenue 11 on Feb 24, 2021. The company, Stars Engrg\'s core business is the installation of fire protection systems, and the work site was used to manufacture fire-retardant wraps. It was found that a ruptured oil jacket in the mixer machine led to the initial blast. This ignited potato starch powder that had accumulated in the air, causing subsequent flash fires. In a walk through scan of the workshop in March 2021, it was discovered that a part of the wall near the machine, which is shared with a neighbouring unit was missing. **Case Study 2** [Ubi Explosion at Audi Service Centre](https://www.straitstimes.com/singapore/flammable-vapours-from-waste-oil-tank-caused-audi-service-centre-explosion-wsh-council) On 7 March 2023, an explosion blew open a section of the Audi service centre in Ubi, resulting in one injury and the evacuation of 100 people. The explosion was also felt by those working in nearby buildings and sent some running for cover. A person was taken to hospital and about 100 people were evacuated after an explosion. The SCDF noticed that a section of the exterior wall on the side of the building had collapsed. Preliminary investigations have shown that the explosion was caused by the accumulation of flammable vapours in a waste oil tank placed inside a lift motor room.  **1.4.1 Classification of Explosion** Explosion can be classified as a **chemical explosion**, **deflagration** (involving low explosives) or **detonation** (involving high explosives) There are two types of **chemical explosion** involving flammable gas/vapor or combustible dust. The key to explosion prevention is avoiding and eliminating: - **Explosive atmosphere** (e.g. installing exhaust ventilation, regular removal of dust accumulation) and - **Ignition probability (**e.g. use of intrinsically safe equipment, classifying hazardous and equipment areas) The hazardous area and equipment classification is based on [International Electro-Technical Commission (IEC)](https://www.iec.ch/homepage) e.g. the work areas are classified as Zone 0, 1, 2 for areas where there are flammable vapors. (see Fig. 5) *Fig. 5* Updated: 30 August 2024 \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_