One of the more common emergencies that happen in residential and office buildings is a fire. It can happen for any number of reasons, most of which are avoidable, if only with the practice of due diligence and care. Not only is it destructive to property, it is also highly dangerous for the lives of the people trapped in it. In fact, it is not necessarily the fire that brings the most harm to the occupants, but rather, the smoke, which could travel fast, clog up the hallways, and suffocate the people.
Reasons Why Fire Spreads
The following are the reasons why fire could spread in the workplace:
- No fire detection system in place
- No alarm system in place
- Workers not knowing or confusing the sound of an alarm
- The fire starts in an unoccupied area
- Fire starts out of normal work hours
- Absence of compartments in building structure
- Inappropriate storage of materials
Principles of heat transmission and fire spread
Fire transmits heat in several ways, which need to be understood in order to prevent, plan escape from, and fight fires. Heat can be transmitted in the following ways:
- Convection
- Conduction
- Radiation
- Direct burning.
Understanding these can help us in firefighting and prevention in the workplace.
- Convection
This is defined as the transmission of heat within a liquid or gas and is due to their difference in density. Heated liquid or gas expands and becomes lighter, thereby becoming displaced by its heavier counterpart. When this happens, oxygen is drawn in, further inciting the chemical chain reactions.
The rising gases, meanwhile, go up to fuel the upper floors. In an enclosed setting, such as in a confined office space, the movement of the fire will most likely force the gases lower in height as the heated gases spread along ceilings and walls. Superheating then occurs in the fire, thereby causing it to rise further, but this time, carrying with it products of incomplete combustion, such as embers.
- Conduction
This is the transmission of heat through a material with sufficient intensity to melt or destroy the fabric and ignite combustible materials which come into contact or close to a hot section.
Metals like copper, steel and aluminium are very effective or good conductors of heat. Other materials like concrete, brickwork and insulation materials are very ineffective or poor conductors of heat.
Poor conductors or good insulators are used in fire protection arrangements. When a poor conductor is also incombustible, it is ideal for fire protection. Care is necessary to ensure that there are no other issues, such as health risks, with these materials.
- Radiation
Often in a fire, the direct transmission of heat through the emission of heat waves from a surface can be so intense that adjacent materials are heated sufficiently to ignite. A metal surface glowing red-hot would be typical of a severe radiation hazard in a fire.
- Direct Burning
This is the simplest way to spread fire through direct application. A lit match can easily burn paper, for example. The more objects the fire gets in contact with, therefore, the bigger the probability that the fire will be able to spread faster. Because of the characteristics of fire, which is very transient and can affect other objects, it makes it very susceptible to spreading. Once it spreads, it can go from one place to another, making it very difficult to control.
Fire and Smoke spread in buildings
Where fire is not contained and people can move away to a safe location, there is a little immediate risk to those people. However, where fire is confined inside buildings the fire behaves differently.
The smoke rising from the fire gets trapped inside the space by the immediate ceiling, then spreads horizontally across the space deepening all the time until the entire space is filled.
The smoke will also pass through any holes or gaps in the walls, ceiling or floor and get into other parts of the building. It moves rapidly up staircases or lift wells and into any areas that are left open, or rooms which have open doors connecting to the staircase corridors.
The heat from the building gets trapped inside, raising the temperature very rapidly. The toxic smoke and gases are an added danger to people inside the building, who must be able to escape quickly to a safe location.
Another thing that must be noted when it comes to fire is that it has that which is called the flashpoint. This is the lowest temperature at which enough vapour is given off to produce a flammable mixture with air.
This will then cause a momentary flash upon application of the flame, although it will not necessarily continue to burn. If the liquid temperature is below the flashpoint, then the vapour will not ignite.
Containing Fire spread using the principles of fire extinction
With the many possible ways for fire to spread, it is all the more important that proper techniques and methods are taught to building occupants so that they may implement it to contain fire.
The sooner that an attempt to quell it is made, the bigger the chances fire won’t spread and get bigger. Briefly, there are four methods of fire extinction that could prove to be a lot of help in fire fighting and prevention.
- Cooling
Reducing the ignition temperature by taking the heat out of the fire using water to limit or reduce the temperature.
- Smothering
Limiting the oxygen available by smothering and preventing the mixture of oxygen and flammable vapour by the use of foam or a fire blanket.
- Starvation
Limiting the fuel supply By removing the source of fuel by switching off electrical power, isolating the flow of flammable liquids or removing wood and textiles, etc.
- Chemical reaction
This is by interrupting the chain of combustion and combining the hydrogen atoms with chlorine atoms in the hydrocarbon chain.
When attempting to extinguish a fire, remember though that sometimes the fire is just too big, and spreads too fast, such that taking on these measures is only going to make it even more dangerous for the responders.
In this case, the next best thing is to make sure that everyone is removed from the proximate area of the emergency, and that they are safe not only from the fire but also from the dangers of possible smoke inhalation.
With the many possible ways for fire to spread, it is all the more important that proper techniques and methods are taught to building occupants so that they may implement it to contain fire.
Fire safety becomes everyone’s job at a worksite. Employers should train workers about fire hazards in the workplace and about what to do in a fire emergency. If you want your workers to evacuate, you should train them on how to escape. If you expect your workers to use fire fighting equipment, you should give them appropriate equipment and train them to use the equipment safely.
Gabson Professional School of Safety and Engineering provides various health and safety training.
Contact us: www. gabsonschool.com.ng. Call us at +234 818 430 4186 or at info@gabsonschool.com.ng for more information.
