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
Types of Electrical Energy
- Resistance
- Arcing
- Sparking
- Static Electric Charge
- Lightning
9 primary classes of hazardous material
Class 1: Explosives.
Class 2: Gases.
Class 3: Flammable and Combustible Liquids.
Class 4: Flammable Solids.
Class 5: Oxidizing Substances, Organic Peroxides.
Class 6: Toxic Substances and Infectious Substances.
Class 7: Radioactive Materials.
Class 8: Corrosives.
Class 9: Miscellaneous Hazardous Materials
What is Class 1?
Explosives: Any chemical compound, mixture, or device, the primary purpose of which is to function by explosion, with substantially instantaneous release of gas and heat
What is Class 2?
Gases: Any compressed gas meeting the requirements for lower
flammability, flammable range, flame projection or propagation.
Class 3 ?
Flammable and Combustible Liquids
Flammable liquids - any liquids having a flash point
below 100°F.
* Combustible liquids - any liquids with a flash point at or
above 100°F
What is Class 4 ?
Flammable Solids
Any solid material, other than an explosive, likely to cause
fire through friction-contained heat
What is Class 5 ?
Oxidizers: Any substance that yields oxygen readily to stimulate the combustion of organic matter.
What is Class 6?
Poisons & Infectious Substances
* Poison A - Immediately Dangerous to Life or Health (IDLH)
* Poison B - health hazard
* Irritating materials - fumes, tear gas
* Etiological agents - microorganisms that may cause
human disease, anthrax, rabies, tetanus
What is Class 7 ?
Radioactive Materials: Any material or combination of materials that emits poisoning
radiation.
What is Class 8 ?
Corrosives: Any material or solid that causes visible destruction of human skin or a liquid that has a severe corrosion rate on steel.
What is Class 9 ?
Miscellaneous: Other nasty stuff that doesn’t meet the other criteria like Hazardous waste
NFPA 704 Diamond helps to
determine
what, if any, specialty equipment should be used,
procedures followed, or precautions taken during
the first moments of an emergency response
NFPA 704 Diamond red represents
flammability hazard
NFPA 704 Diamond blue represents
health hazard
NFPA 704 Diamond yellow represents
reactivity hazard
Stages of Fire Development
- Ignition
- Growth
- Flashover
- Fully-developed
- Decay
What is Ignition Stage?
Stage where fuel and oxygen are exposed to heat, resulting in a sustained chemical reaction
What is Growth Stage?
Plume development and development of ceiling layer
What happens in the plume development ?
Plume begins to develop and the temperature of fire gases decreases as these gases move away from centerline of plume
What happens in the development of ceiling layer stage?
Overall temperature in compartment increases and the temperature of gas layer at ceiling increases
What is the Flashover Stage?
The stage of a fire at which the combustible contents of a compartment are totally in flame.
What is Fully-developed Stage?
A fully developed fire is the hardest to suppress because, at this point, the fire is at maximum temperatures and causing the most heat damage. If you’ve failed to suppress it before this point, then your odds of stopping the fire are much smaller.
What is Decay Stage?
The decay of a fire is the phase when the fire decreases in intensity until it is either a smolder or non-existent.
Factors that affect fire development
- Ventilation openings
2.Compartment volume - Compartment’s thermal properties 4. Ceiling height
- Initial fuel package
- Additional fuel targets
What is Thermal layering?
Thermal layering is the tendency of gases to form layers according to temperature
What is Heat stratification?
Heat stratification is when the hottest gases form top layers; cooler gases form bottom layers
What is thermal balance?
Thermal balance is where there is no disruption of heat stratification
What is thermal imbalance?
Thermal imbalance is the Disruption of heat stratification (hot gases mix throughout compartment)
5 FIRE/FUEL CLASSES
Class A
Class B
Class C
Class D
Class K
What are Class A Fire Type?
Ordinary Combustibles such as wood, paper and cloth.
What are Class B Fire Type?
Flammable Liquids and Gases
What are Class C Fire Type?
Live Electrical Equipment
What are Class D Fire Type?
Combustible Metals
What are Class K Fire Type?
Combustible Cooking
How to extinguish a Class A fire type?
- Cooling with Water
- Quenching with Water or Class A Foams
How to extinguish a Class B fire type?
- Inhibiting Chemical Chain Reaction
*Smothering/Blanketing - Removing Fuel
- Reducing Temperature
How to extinguish a Class C fire type?
- Nonconducting
Extinguishing Agent
(Halon, Dry Chemical,
Carbon Dioxide) - Deenergizing and Treating as Class A or Class B Fire
How to extinguish a Class D fire type?
Blanketing with Special Agents, Especially Fuel Specific Dry Powders
How to extinguish a Class K fire type?
Saponification is the quickest and most effective way to fight class K fires
How to extinguish a Class C fire type?
Blanketing with Special Agents, Especially Fuel Specific Dry Powders
What is Autoignition?
Autoignition is defined as the self-ignition of the vapors emitted by a liquid heated above its ignition temperature and that, when escaping into the atmosphere, enter into their explosive range.
