-
What is a fire?
A fire is a chemical reaction involving rapid oxidation (combustion) of fuel
-
What is usually the oxidizer and reducing agent in a fire?
The oxidizer (gives electrons away to become reduced) is usually oxygen, and the reducing agent (which becomes oxidized) is the fuel.
-
What are the elements of of a fire triangle?
- - Fuel (reducer)
- - Oxygen (the oxidizer)
- - Heat (needs to approprate temperature to ignite fuel)
-
What are the four classes of fire?
- - A - Ordinary combustibles (paper, clothing)
- - B - Flammable liquids (petroleum oil)
- - C - Electrical Fires
- - D - fire in combustible metals.
-
What percentage of the air is oxygen?
21%
-
Which of the following requires the the lowest time to ignite? gas, vapour or solid.
Gas and vapour may be ignited with a spark, where as a solid may require longer heat source.
-
What does vapor density tell us?
A vapor density greater than air, the vapor will settle at ground level, and vapor density less than air would move upwards.
-
What is a flash point?
The minimum temperature at which the vapor above a liquid will first support a combustion transient (or "flash")
-
What are the two types of flash points usually given? Which is usually higher?
Usually, open cup and a closed cup flash point is given relating to how the flash point was found. Usually the open cup is a few degrees higher than the closed cup.
-
What does the term flammable mean?
Flammable is used for liquids with flash point below 100 degree F or 37.8 C
-
What does the term combustible mean?
The term combustible is used for liquids with a flash point above 100 degree F or 37.8 C
-
What is the fire point?
It is the temperature at where the flash becomes self sustaining.
-
What is the lower flammable limit (LFL) or lower explosive limit (LEL)?
The lowest concentration of a chemical (by volume of partial pressure) in air that will support combustible (fuel)
-
What is the upper flammable limit (UFL) or the upper explosive limit (UEL)?
The upper flammable limit is the maximum concentration of a chemical (by volume or partial pressure) in air that would be combustible.
-
What is the autoignition temperature?
Autoignition temperature at which the solid, liquid or vapour will spotaneously ignite resulting in a self sustaining fire.
-
What is minimum ignition energy?
Minimum ignition energy is the lowest energy that would be required to ignite a flammable mixture via electrical discharge
-
What is burning velocity?
Burning velocity is the speed at which the smooth flame moves into a stationary mixture of reactants.
-
What is the stoichiometric ratio?
- Stoichiometric ratio is the optimal ratio between fuel and oxidizer that will result in the optimal combustion and heat release.
- "lean" means not enough fuel
- "rich" means enough fuel or too much
-
What are the three methods of heat transfer?
- Conduction
- Convection
- Radiation
-
What is conduction?
- Conduction is heat transfer through a solid
- can be through molecular motion or movement of free electrons
-
What is convection?
- Convection is heat transfer through a fluid
- Forced convection and natural convection
-
What is radiation heat transfer?
- Radiation does not require a medium to transfer heat (i.e. thermal radiation)
- Reflected, absorbed or transmitted
- (through)
-
The tw oeffects of confined fires are
- confining the flame and combustion products
- restricting the ventilation supply of fresh air to the fire
-
For a liquid to ignite, three conditions must be satisfied:
- liquid must vaporize
- vapor must mix with air
- ignition source to obtain self-propagation of the flame must be available
|
|
