Sem#2 Chap 6 Flashcards
Define Fire and how its made (not like flame lol)
Fire is combustion
combination of oxygen with carbon and organic material (fuel) in a rapid chemical reaction that produces flame, heat, and light.
Corrosion
An oxidation-reduction reaction in which
a metal is oxidized, and oxygen is reduced, usually in the presence of moisture.
Also known as rusting. Identical to the combustion reaction, only much, much slower
How does fire occur? What must be present?
Fire occurs when fuel, oxygen and heat are
present in the right combination; these three
critical components are referred to as the fire
triangle.
Any combustible material is fuel.
Heat Release Rate
is rate at which fire releases energy — also known as power — and is measured in units of Watts (W).
Heat Flux
rate of heat energy transferred per unit surface area — and is measured in units of kW/m^2
Heat is ALWAYS transferred from ________ object to _____ object
hotter object to cooler object
Three types of heat transfer
- radiation,
- conduction, and
- convection
Rate of Heat Transfer Fromula: Electro Magnetic Waves
Slide #7 Lect #6
Conduction is heat transfer within solids or
between contacting solids: Formula
Slide #8 Lect6
Thermal conductivity of Common building materials
High to Low
Copper = 387
Steel = 45.8
Glass = 0.76
Brick = 0.69
Water = 0.58
Gypsum = 0.48
Oak = 0.17
Pine = 0.14
PPE = 0.034 - 0.136
Air = 0.026
Convection
is heat transfer by movement of
currents of liquids or gases.
Structural Fires
Fire starts in a structure with doors and windows closed
Early growth has adequate oxygen to mix with heated gases, which results in flaming combustion.
As oxygen level within structure is depleted, fire decays, heat release decreases and temperature decreases.
Structural Fire are limited by???
The amount of oxygen
FLASHOVER
When a structural fire has a vent opened (like a door or window)
Transition phase in development of a contained fire in which surfaces exposed to thermal radiation, from fire gases in excess of 600°C, reach ignition temperature more or less simultaneously and fire spreads rapidly through the space. The most dangerous and most smokey stage of fire development.
How to Operate a Fire Extinguisher
P: Pull
A: Aim
S: Squeeze
S: Sweep
Most fire deaths are caused by??
Smoke inhalation
The Major Causes of House Fire Fatalities
House fires can incapacitate or kill by reducing oxygen
levels,
* either by consuming the oxygen,
* or by displacing it with other gases.
Heat is also a respiratory hazard, as superheated gases burn the respiratory tract. When the air is hot enough, one breath can kill.
Smoke is made of components:
- Particles: Unburned, partially burned, and
completely burned substances can be so small they penetrate the respiratory system’s protective filters, and lodge in the lungs. Some are actively toxic; others are irritating to the eyes and digestive system. - Vapors: fog-like droplets of liquid can poison if inhaled or absorbed through the skin.
- Toxic Gases
A. Carbon monoxide (CO): the most common; can be deadly, even in small quantities, as it replaces oxygen in the bloodstream.
B. Hydrogen cyanide: results from burning plastics, such as PVC pipe, and interferes with cellular respiration.
C. Phosgene: formed when household products, such as vinyl materials, are burned. At low levels, phosgene can cause itchy eyes and a sore throat; at higher levels it can cause pulmonary edema and death.
Carbon monoxide (CO):
the most common; can be deadly, even in small quantities, as it replaces oxygen in the bloodstream.
Carbon Monoxide formation
When any fire burns, in an enclosed room, the amount of oxygen available gradually decreases.
* At the same time the amount of carbon dioxide increases.
* As the amounts of these two gases change, this causes the combustion process to alter from one of complete combustion to one of incomplete combustion.
* This results in the release of increasing amounts of CO.
Hydrogen cyanide:
results from burning plastics, such as PVC pipe, and interferes with cellular respiration.
Phosgene:
formed when household products, such
as vinyl materials, are burned. At low levels,
phosgene can cause itchy eyes and a sore throat; at higher levels it can cause pulmonary edema and death.
Fire Proof the Inside of Your House
Slide #20 Lect #6
Wild Fires have Limited and Unlimited what?
Limited: Fuel
Unlimited: Oxygen
Photosynthesis
In photosynthesis, plants take in water (H2O), carbon dioxide (CO2) and use energy (the sunlight) to build their organic material.
* Oxygen is given off as a by-product.
Wildfire Photosynthesis
In fire, plant material (such as cellulose, main component of wood) is heated to ignition, and combustion occurs, when oxygen begins combining rapidly (explosively) with the organic material.
In effect, the combustion (burning) of forest vegetation is photosynthesis reaction in reverse, where solar energy stored by plants during their growth is released to the atmosphere
during fire.
Why Does Nature Need Wild Fires?
Through photosynthesis, plants grow and collectively produce large volumes of trunks, branches, leaves, needles, grasses, and such.
- Photosynthesis causes buildup and storage of chemical potential energy in plants that is released during fire.
The mass of organic material is recycled either:
* by the combined effects of slow decomposition (basically very, very slow combustion) through rotting and digestion
* or by the rapid burning through wildfire.
Where Wildfire are not needed to clean house
Deserts and Tropics
In a tropical rain forest with abundant warmth and moisture, rotting decomposes dead vegetation and recycles the nutrients for the production of new plant material via photosynthesis.
In deserts, there is little moisture for either plant growth or decomposition, Here wildfire does not need to be frequent in deserts; not much plant material/fuel to burn to begin with.
