Chemistry & Physics of Fire Flashcards
What are the three (3) essential elements for ignition?
Fuel, Heat, Oxygen
What are oxidizers?
Substances that acquire electrons from fuel in a chemical reaction and release oxygen during combustion.
What are some of the most common oxidisers in combustion?
Fluorine, chlorine, hydrogen peroxide, nitric acid, sulfuric acid
What is an Ignition Source?
The Heat energy is required to start the combustion process.
What is combustion?
An exothermic chemical reaction between some substance and oxygen (oxidation).
What is oxidation?
This is a chemical reaction in which two materials—an oxidizing agent and a reducing agent - combine to form a product less reactive than the parent materials.
Instant oxidation can lead to
an explosion
Rapid oxidation can lead to
a fire
Very slow oxidation can lead to
rust and yellowing paper
What are the products of combustion?
- Fire gases
- Flame
- Heat
- Smoke
Products of Fire Gases
Carbon monoxide, Carbon dioxide, Hydrogen cyanide, Hydrogen chloride, Acrolein, Oxygen Deficiency
5 Unique Fire Phenomena
Explosion
Deflagration
Detonation
Flashover
Backdraft
What is the main difference between a fire and an explosion?
The rate at which energy is released
What is Deflagration?
Deflagration is the burning of a gas or aerosol that is characterised by a combustion wave.
What is Detonation?.
Detonation is the burning of a gas or aerosol characterized by a shock wave with a sonic “boom”.
When does flashover happens?
The temperature reaches the ignition temperature of the majority of combustibles in the area, there is spontaneous combustion of the combustibles in the area.
What is Backdraft?
Backdraft is a fire in an enclosed area that consumes the oxygen supply and generates CO and heat.
Signs of Potential Backdraft
- Pressurized smoke exiting small openings
- Black smoke becoming dense gray yellow
- Confinement and excessive heat
- Little or no visible flame
- Smoke leaving the building in puffs or at intervals
- Smoke-stained windows
What is Heat?
Heat is energy transferred from one body to another when temperatures are different
What is temperature?
Temperature is a measure of warmth or coldness or an object
based on some standard (usually freezing and boiling points).
Temperature Units
- Celsius
- Fahrenheit
- Kelvin
- Rankine
Heat Units
- Joule
- Calorie
- British Thermal Unit (Btu)
Heat Transfer Types
- Conduction
- Radiation
- Convection
What is Conduction?
Conduction is the transfer of thermal energy from one substance to another through direct contact
What is radiation?
Heat is energy and has the ability to travel in a straight line through space until it is stopped by some object.
What is Convection ?
Convection is heat energy can be transferred by circulation of a fluid,
such as air or a liquid
4 Sources of Heat Energy
- Chemical
- Electrical
- Mechanical
- Nuclear