Chapter 10 - Fire Protection and Prevention Flashcards
Combustion
chemical reaction between fuel and oxidizing agent that produces energy in the form of heat and light. When fuel burns, carbon reacts with oxygen and can form either carbon monoxide or carbon dioxide.
Heat of combustion
amount of heat in calories evolved by the combustion of 1 g weight of a substance
Flammable liquid
Any liquid with a flash point below 140 F and having a vapor pressure not exceeding 40 psia at 100F
Combustible liquid
Any liquid having a flash point at or above 140 F and below 200 F
Flash point
Minimum temperature at which a liquid gives off vapor within a test vessel in sufficient concentration to form an ignitable mixture with air near the surface of the liquid. The flash point is normally an indication of susceptibility to ignition
Lower flammability limit
Lower end of the concentration range of a flammable solvent at a given temperature and pressure for which air/vapor mixtures can ignite. The lower flammability limit (LFL) is usually expressed in volume percent
Upper flammability limit
Maximum concentration of a combustible substance capable of propagating a flame through a homogenous combustible mixture. The upper flammability limit (UFL) is usually expressed in volume percent.
Three primary methods of heat transfer
Radiation
Convection
Conduction
Radiation heat
The amount of thermal radiation between two or more objects (bodies). Radiation travels in wavelengths and does require that the two objects be in contact, as radiation can travel through a vacuum or space.
Heat Transfer by Convection
Process whereby thermal energy is transferred by movement of a heated fluid such as liquid or air
Heat transfer by Conduction
Transfer of thermal energy between two objects in contact with each other
Four components necessary to sustain combustion
The Fire Tetrahedron
Fuel, Oxygen, Heat, and a chain reaction
Class A Fires
Common combustibles such as wood, paper, cloth, rubber, trash, and plastics. Common in typical commercial and home settings, but can occur anywhere these types of materials are found
Class B Fires
Involve flammable liquids, gases, solvents, oil, gasoline, paint, lacquers, tars, and other synthetic or oil based products. Class B fires often spread rapidly and unless properly secured, can reflash after the flames are extinguished
Class C Fires
Involve energized electrical equipment, such as wiring, controls, motors, data processing panels, or appliances. They can be caused by a spark, power surge, or short circuit, and typically occur in locations that are difficult to reach and see
Class D Fires
Involve combustible materials such as magnesium and sodium. Combustible metal fires are unique industrial hazards that require special dry powder agents to extinguish
Class K Fires
Involve combustible cooking media such as oils and grease commonly found in commercial kitchens. Require a special wet chemical extinguishing agent that is specially suited for extinguishing and suppressing these extremely hot fires that have the ability to reflash
Fire extinguishers
Important to consider the classification of fire when selecting
The labeling system indicates which kind of fire it can be used for
Also have number ratings to indicate how large of a fire it can contain
Portable fire extinguishers shall be serviced
annually, and hydrostatically tested at 5 or 12 years depending on their shell
Portable Fire Extinguishers Hydrostatic Testing
Required
when unit has been repaired by soldering, welding, brazing, or use of patching compounds
When cylinder or shell threads are damaged
When there is corrosion that caused pitting, including corrosion under removable name plate assemblies
When the extinguisher has been burned in a fire
When a calcium chloride extinguished agent has been used in a stainless steel shell
Fire extinguisher inspections and service requirements
The employer is responsible for ensuring that inspection, maintenance, and testing of all portable fire extinguishers is conducted. Visual inspection monthly and annual servicing and testing.
Dry Pipe Sprinkler Systems
Normally installed in areas where there is a potential for freezing such as garages, unheated building or outside canopies. Water is not present in pipe until system is triggered. Only used if ambient temperature range reaches below 40F
Wet Pipe Sprinkler systems
Water present at all times. Most frequently installed system
Deluge sprinkler systems
Installed in areas where there are special hazards where the rapid spread of fire is a major concern. No water stored in the distribution system, no heat sensors on sprinkler heads. Water released by activation of a deluge valve which is activated by fire alarm. Must be manually reset.
