Hello everyone, Welcome to FEM111 Fire Safety Management. My name is Ivan and I will be your facilitator for the course. This is the first topic of the study unit and we are going to begin by understanding the chemistry and physics of fire - Basic Fire Science. Basic fire science is one of the key elements in an effective fire safety management. Understanding the principles of fire and explosion enable us to recognise the associated fire hazards, know how a fire will start and spread, identify the fire prevention measures that we can put in place. The same applies to explosion.
At the end of this study topic, you will be able to discuss the chemistry of fire; discuss the fire dynamics in a compartment fire; and explain the hazards associated with a confined fire.
To achieve these objectives, we will approach this topic by asking layman questions, such as: What is a fire? And begin by understanding it at scientific level; looking at the chemistry of fire and the interaction between fire triangle and fire tetrahedron. How to prevent unwanted fire? With the application of the principles of fire prevention. How fire starts and spreads? Looking at the stages of combustion, principles of fire spread, and recognise the dangers of their associated fire phenomena such as thermal rollover, flashover, and backdraft. How are fires being classified? With respect to the fuel source characterisation such as flashpoint, flame-point, vapour density, etc.
With better understanding of what fire is all about, we can then move on to look at Explosion. We ask logical questions like: What is an explosion? Look at the mechanism of explosion, and associated dangerous phenomena. How to prevent unwanted explosion? Through the principles of explosion management, and area classification. How are explosions being classified? Looking at various types of explosions.
For the longest time, scientists have been trying to establish when was fire first invented, discovered, used, and controlled by mankind? Research has so far shown that fire has been used by the early human ancestor as early as 3.2 million years ago during the Early Stone Age. Cooked food was documented some 2 million years ago with evidence of flint tools having tell-tale signs of fire contact. But the widespread control of fire was only dated back to some 400,000 years ago as we continue to better understand the sciences behind fires. Now, mankind may never get to find out exactly when was fire invented or discovered. Fire has most probably existed as long as oxygen and fuel sources have been around; hence there is no need to invent fire, it is a natural reaction by itself, and has been around for millions of years. Fire has been used by mankind to cook food and heat up home during cold winter; fire has also caused many tragic events resulting in injuries and death. Therefore the need to under fire science is paramount for effective fire safety design and fire safety management. The power of fire cannot be underestimated; manage it well it will serve you as a good servant, lost control of it it can be a really bad master over you; a famous quote by Thomas Carlyle (A
Scottish Historian) in 1843; and all fire engineers around the world will testify this!! What s more critical is How well can we manage and control Fire? This stem in how well we understand this friend or fiend of ours thus the importance of fire science.
So, let s begin by asking ourselves What is a fire?
We said that fire is a reaction; a chemical reaction to be specific. For a reaction to take place constituent A will react with constituent B in the action of applied heat to give rise to product C and D. In this case, A is the fuel, B is oxygen. When the applied heat source is great enough to cause the reaction to move from left side to the right side of the equation, a chemical reaction had taken place, resulting in products C and water as product D. Examples of these are like burning or combustion of methane or propane gas in the presence of oxygen, giving rise to by-products such as carbon dioxide and water; this is exactly what we do when we turn on our cooking stove to boil water or cook our meals. Don t worry and don t freak out as yet this is probably the only time you will see chemical equation in this course. Nonetheless, to simplify learning, the visual on the right showed the chemical reaction of how fuel, oxygen and ignition heat source result in a fire combustion process, giving rise to products such as smoke (including fire gases like phosgene, hydrogen chloride gas, etc.) and heat. Notice how the heat produced feedback and contribute to back to the ignition heat source to sustain the combustion process.
Key point, Fire is therefore a chemical reaction called Combustion; a rapid oxidation process that combined fuel and oxygen in the presence of sufficient heat energy. So, to answer our very first question, What is a Fire? Fire is a chemical reaction, a rapid oxidation reaction called combustion that combined fuel and oxygen with the applied ignition source, resulting the release of products such as smoke, heat, and light in different intensity
This brings us to the all familiar fire triangle; a fundamental concept and theory to fire science. Now, you may be thinking that this is so elementary and why are we still talking about it now in a degree program? Well, don t underestimate the value of this simple yet effective fire triangle; there is more to this triangle that we need to appreciate. Being a prospective fire safety manager, you must be able to use this triangle to educate your charges as you go about implementing an effective fire prevention program.
Let s begin by asking ourselves fundamental questions about the fire triangle: Q1: Amongst the 3 elements, which element is MOST difficult, if not impossible, to control? Oxygen it is present almost everywhere and we need it to sustain life; thus almost impossible to totally control it. Q2: Which element as much as we would like to control, can almost always control, but still pretty elusive and cannot be totally eliminated? Ignition Sources there are bound to exist in our daily life as we use electrical appliances, machineries, etc. Q3: Which element we are definite that we can control effectively? Fuel we can effectively control the exposure of combustible materials to heat sources, manage loss of containment, etc. And this element is closely knitted to Housekeeping and Stowage Management
This brings us to the next question, How do we prevent unwanted fire? And obviously, based on the fire triangle, there will be 3 fundamental principles of fire prevention. With the better understanding of the fire triangle, what do you think should be the primary approach to effective fire prevention?
I hope you therefore see the logical flow that the 1 st principle of fire prevention would be effective control of fuel. This is something which we can definitely manage and control well if we put in the rigor of fire safety management. Good control of fuel will prevent any unnecessary exposure of combustible materials (regardless if the ignition sources are present). This measure alone will eliminate the fire triangle from existence. And if exposure is unavoidable due to work processes, then preventing a combustible fuel-air mixture through methods such as local exhaust ventilation, dilution ventilation, permit to work systems, and having a fire watch will ensure effective fuel control. Well, I hope you have begun to see the fire triangle slightly differently from now on.
The 2 nd principle of fire prevention would be through the effective control of ignition sources in the surrounding environment. This is something which we cannot totally manage and control because of the unlimited possibilities of trivial heat sources such as welding hot-works, smoking, cutting activities; including hot surfaces from the electrical appliances and equipment that we need to use on a daily basis. As much as possible, control of ignition sources will eliminate, avoid, reduce and prevent any probable ignition. This measure will only reduce the probable existence of fire triangle. This can be achieved through methods such as equipment bonding and grounding, area classification, equipment classification and permit to work systems to ensure effective ignition control.
The 3 rd principle of fire prevention would be through effective control of oxygen. Again, this is something which we probable find most difficult to manage and control because oxygen is everywhere. Ironically, it is needed to support life as well as the fire combustion reaction. And at the normal 21% concentration, it supports combustion; but at higher than 23% concentration, it enhances combustion process furiously. In addition, this element can also exist as a chemical compound that contribute oxygen in the reaction process, called an oxidiser. As such, the controls of oxygen become a challenging balance between life-support and combustion-support. This measure will only minimise the existence of fire triangle. This can be achieved using nitrogen or other inert gases, blanketing with vapoursuppressing foam, and engineering approach to limit oxygen concentration via the flammability diagrams of respective material.
Alright, let s stop for a quick catch-up with the big picture in fire science development. Don t go away with the idea that fire science is just all about the fire triangle. Fire triangle and its principles of fire prevention is the backbone for you as prospective fire safety manager. Fire science is more complex than the triangle. In fact, the science of fire and explosion has evolved from a 2-dimensional fire triangle, to a 3-dimensional fire tetrahedron, back to a 2-dimensional fire pentagon, and in today s context, looking at the 3-dimensional fire pentagonal pyramid; studying into complex behaviours of fire from fire initiation, to fire dynamics, to flame spread, flame colours, heat intensities, and effects on building materials, etc. It is not the intent of this topic to dive into the depth of fire science, and this stopover is just about good to put you in perspective about fire protection engineering.