Heat Transfer

Heat Transfer and its Methods

  • Heat transfer is fundamental to understanding the principles of how fires start, spread and can be controlled.
  • It’s important to know that heat always moves from a warmer object to a cooler one.
  • There are three methods of heat transfer: conduction, convection, and radiation.


  • Conduction occurs when heat moves between two objects in direct contact with each other.
  • An example of this is a metal spoon heating up when it’s placed in a hot drink; heat from the hot liquid moves to the cooler spoon until their temperatures are equal.
  • Solids, especially metals, are generally good conductors of heat, while liquids and gases are less effective.


  • Convection is the heat transfer method that occurs in fluids, which include both gases and liquids.
  • It involves the movement of warmer fluid particles rising and being replaced by cooler fluid particles in a circular motion.
  • In a fire, hot gases created by combustion rise due to this principle.
  • Convection can allow a fire to spread along ceilings and other upper areas even though the primary fire source may be located lower.


  • Radiation is the only method of heat transfer that doesn’t require a medium (like a gas, liquid, or solid) to move through.
  • Radiant heat travels in straight lines and can be reflected, absorbed, or transmitted when it meets a surface.
  • Fire spreads by radiation when the heat radiates out from the flames and heats up surrounding materials.
  • Once these materials reach their ignition temperature, they can also catch fire, allowing the fire to spread further.

Fire Investigation Importance

  • Understanding the methods of heat transfer is crucial in fire investigation.
  • This knowledge can help pinpoint the start of the fire, the materials first set on fire, and the direction the fire spread.
  • It also can assist in validating witness statements and assessing possible causes of the fire.

Remember, being able to identify and comprehend these fundamental science principles can be extremely useful, not only in understanding how fires behave, but also in how to prevent, control, and investigate fires.