Chapter 15: Fire Hazards and Life Safety
Flammable liquids have a flash point below...
99.8 degrees Fahrenheit (37.7C)
Exit discharge
Any part of the exit route that leads directly outside of the building or to an open space that has access to the outside
fire safety programs include (possible essay?)
Assessment planning awareness and prevention
Class D fires
Fires involving combustible metals such as magnesium, titanium, zirconium, sodium, and potassium.
OSHA 29 CFR 1910.134
Respiratory Protection
Conduction
The direct transfer of heat from one substance to another substance that it is touching. direct thermal energy transfer
Radiation
The transfer of energy (heat to solid) by electromagnetic waves
Class A fires
Usually involve wood, paper, cloth, or cardboard and typically happen in dry-storage areas, dining areas, garbage areas, and restrooms.
Fire (combustion)
a chemical reaction between oxygen and a combustible fuel
Carbon monoxide
a colorless, odorless toxic flammable gas formed by incomplete combustion of a fuel. Most fires lack oxygen and produce heavy amount of monoxide
Fire is a chain reaction. For combustion to continue there must be...
a constant source of fuel, oxygen, and heat
Exit routes
a continuous and unobstructed path of travel from any point within a workplace to a place of safety. three components: exit access, exit, and exit discharge (2 are generally required and must be unlocked from inside)
Hypergolic reaction
a violent reaction occurring when a fuel and oxidizer are mixed. The mixing of liquid hydrogen and liquid oxygen is also an example of this reaction.
Hot work
according to OSHA standards, any riveting, welding, flame cutting or other operation which produces sparks and/or fire. Programs should be in place for these jobs
Exit
any part of the exit route that provides a means of access to the exit discharge
Combustible liquids have a flash point
at or higher than flammable liquids
Almost everything in an industrial environment
can burn
The number one killer in fires
carbon monoxide
Smoke
combination of gases, air, and suspended particles
Explosive range (flammable range)
concentrations of a vapor or gas in the air that can ignite from a source
Fire hazards
conditions that favor fire development or growth
Heat transfer is accomplished by...
conduction radiation convection
Endothermic reaction
consumes more heat they they generate
Exothermic reaction
create heat
Photoelectric Fire sensors
detect changes in infrared energy that is radiated by smoke (often from smoke particles obscuring the photoelectric beam)
National Fire Protection Association (NFPA)
devised the NFPA 704 system for quick identification of hazards when presented substances burn used red (flammability), yellow (reactivity), white (special information), and blue (health) triangles that are used on product labels, shipping cartons, and building. ratings in each triangle go from 0 to 4 with 4 being the most severe hazard level
Permissible exposure limit
expressed in parts of vapor per million parts of contaminated air (important because many vapors present inhalation hazards as well as fire hazards)
Special category fires
extremely active oxidizers or mixtures, flammables containing oxygen, nitric acid...
Fire extinguisher systems
fire brigades standpipe and hose systems automatic sprinkler systems (fixed)
Products of combustion
gases, flame (light), heat and smoke
Heat always flows from
higher temperature to lower temperature
A major cause of industrial fires is
hot, poorly insulated machinery and processes
Spontaneous combustion
ignition of a substance (as oily rags) resulting from an internal oxidation process (rare)
The principle method of fire suppression..
is passive (the absence of sufficient heat)
By-products of combustion
light and smoke
During the combustion process
materials are broken down into basic elements. loose atoms form bonds with each other to create molecules of substances that were not originally present
Interior structural fire brigade
may fight any type of fire provided it has been issued the appropriate protective clothing and equipment
Performance based standard example
may specify that materials used have a one, two, or four hour fire resistance rating
The major cause of industrial fires is
mishandling flammable liquids and flammable gases
Synthetic polymers
often form deadly fumes when consumed by fire
Elements required to start and sustain fire
oxygen fuel heat
The trend in fire safety standards is toward _____ and away from ____
performance based standards Traditional specification based approach
Explosion
rapid, contained fire
A fire may be extinguished by
removing the fuel source, starving it of oxygen, or cooling it below the combustion point
Traditional specification based approach example
require that brick, concrete, or steel material to be used in a given type of building
OSHA regulations for fire brigades
scope prefire planning organizational statement physical capability training and education firefighting equipment protective clothing respiratory protective devices
Pyrophor hypergolic fuels
self-ignite in the presence of oxygen found at the normal atmospheric concentrations
Fuels occur as
solids, liquids, vapor, and gases
Ultraviolet detectors or infrared detectors
sound an alarm when the radiation from fire flames is detected
What is needed for a reaction to start?
source of ignition (spark or open flame) or a high enough temperature
Electrical lines and sources of heat are also
sources of ignition
OSHA standards for fire protection appear in
29 CFR 1910.156 (subpart L)
Most people die in fires due to
suffocation or breathing smoke and toxic fumes. Many fire extinguishers use carbon dioxide because of its ability to starve the fire of oxygen while simultaneously cooling the fire
Ignition temperature or combustion point
temperature at which a given fuel can burst into flames
The properties of the fuel directly correspond to
the best means of combatting the fire
Fire hazards typically involve...
the mishandling of fuel or heat
Lower flammable limit
the percentage of vapor in the air above which a fire cannot occur because there is insufficient fuel (the mixture is too lean)
Upper flammable limit
the percentage of vapor in the air above which there is insufficient air for a fire (the mixture is too rich)
Combustion
the process where fire converts fuel and oxygen into energy (usually in the form of heat)
In order for liquids and solids to burn
they have to be converted into a flammable vapor by heat
The best way to reduce fires is
to prevent them
Excess heat from a fire is...
transferred to surrounding objects which may ignite, explode, or decompose
Thermal expansion detectors
use a heat sensitive metal link that melts at a predetermined temperature to make contact and sound an alarm
Ionization or radiation sensors
use the tendency of a radioactive substance to ionize when exposed to smoke. the substance becomes electrically conductive with the smoke exposure and permits the alarm circuit to be completed
Incipient fire brigade
used to control only small fires. Requires no special clothing or equipment
If a flammable liquid is lighter than water
water cannot be used to put out the fire
Vapor density
weight of a vapor compared to air
Carbon dioxide is produced
when there is more oxygen than the fire needs. not toxic but can reduce concentration of oxygen in the air
OSHA fire prevention plans
Make a list of all fire hazards in the workplace. record the proper handling and storage procedures for all hazardous materials in the workplace. List potential ignition sources in the workplace and their means of control. record the type(s) of fire protection equipment needed to control all fire hazards in the workplace. Develop and record procedures to control flammable and combustible waste materials.
Fire Tetrahedron
Model of the four elements/conditions required to have a fire. The four sides of the tetrahedron represent fuel, heat, oxygen, and chemical chain reaction.
Auto ignition temperature
The lowest temperature at which a combustible material ignites in air without a spark, source of ignition, or flame.
Flash point
The lowest temperature to which a substance must be heated in order for the substance to give off vapors which will burn when exposed to a flame or ignition source.
Fire point
The minimum temperature at which enough vapors are given off to support continuous burning.
Exit access
The portion of the means of egress that leads to an exit.
Convection
The transfer of thermal energy by the circulation or movement of a liquid or gas
Fires are classified according to:
Their properties: the type of fuel feeding the fire
Class B fires
Usually involve flammable liquids and gases and typically start in kitchens and maintenance areas.
Class C fires
Usually involve live electrical equipment and typically occur in motors, switches, cords, circuits, and wiring.