Fire Hazards Glossary

 Acid gas: A gas that forms an acid when dissolved in water.

Adapter: A device for making a connection when threads do not match or when they are different sizes.

Alarm: Any signal indicating the need for emergency response; also, the device that transmits an alarm.

Alcohol: The hydrocarbon derivative in which a hydroxyl radical (-OH) is substituted for a hydrogen atom and which has the general formula R-OH.

Aldehyde: A hydrocarbon derivative with the general formula R-CHO.

Alkanes: An analogous series of saturated hydrocarbons with the general formula CnH2n+2

Alkyl: The general name for a radical of an alkane; an alkyl halide is a halogenated hydrocarbon whose hydrocarbon backbone originated from an alkane.

Alkynes: An analogous series of unsaturated hydrocarbons with the general formula CnH2n_2; the alkynes all contain just one triple bond between carbon atoms.

Amine: The hydrocarbon derivative in which an amine group (NH2) is

substituted for a hydrogen atom and which has the general formula R-NH2.

Analogue: A compound in one analogous series that has a property common with a compound in another analogous series; for example, methyl chloride is an analogue of methyl fluoride.

Aromatic: The name originally given to cyclical compounds containing the benzene “ring” because the first benzene-type compounds isolated smelled “good”.

Arson: Arson is the willful and malicious burning of the property of another. This meaning has been broadened by statute in many jurisdictions to include one’s own property.

B

Backdraft: The term given to a type of explosion caused by the sudden influx of air into a mixture of gases, which have been heated to above the ignition temperature of at least one of them.

BLEVE (Boiling Liquid Expanding Vapor Explosion): See Boilover; the same phenomenon may occur in a pressurized container, resulting in an explosion or bursting of the tank or vessel in which a fire is occurring. The term is almost exclusively used to describe a disastrous effect from a crude oil fire.

Boiling Point: The temperature at which the vapor pressure of a liquid just equals atmospheric pressure.

Boilover: Crude oil often contains some entrained water and/or an emulsion layer. In addition, crude-oil storage tanks will have some accumulations of water on the uneven tank bottoms. In a fire, when a heat wave is formed and comes in contact with any water, a steam explosion occurs, thus agitating the hot oil above it with great force. The evolution of the steam explosion can be understood by examining the reaction of water to high temperatures. When water is heated to its boiling point of 2120F., water vapor, or steam, is generated. The steam that is produced expands approximately 1,700 times in volume over the volume of the water that boiled away. Should a heat wave of a temperature well above 2120F. contact any water entrained in the oil, or some of the bottom water, which is usually in larger quantities, it can be readily imagined that this instantaneous generation of steam will act like a piston, causing the oil to be flung upward with considerable violence. When the reaction is so strong, it causes the oil to overflow the tank shell. This sudden eruption is what is known as a boilover. Boilovers of sufficient

magnitude, to cascade enough burning crude oil out of the tank to not only cover the entire dike area but even enough to overflow the dike wall as well, have occurred. When the hot oil and steam reaction takes place, the oil is made frothy, or sudsy, which in turn further increases its volume. The reaction resulting from the heat wave contacting entrained water can be expected to be of lesser activity than from contact with bottom water. The reason for this difference is that the quantities of water converted to steam in a given spot are usually less. Of course, with entrained water, there possibly can be several of these “frothover”-type eruptions during the progress of the fire.

Branching: A configuration in which a carbon atom attaches itself to another

carbon atom that has two or three other carbon atoms attached to it, forming

a branch, or side chain. When the carbon attaches to another carbon that has

only one other carbon attached to it, a straight chain is formed, rather than

a branched chain.

BTU: British Thermal Unit: The amount of energy required to raise one

pound of water 1°F.

Building codes: There are several building codes that are widely adopted

throughout the United States: (1) The Southern Standard Building Code; (2)

The Uniform Building Code; (3) The Basic Building Code; (4) The National

Building Code; and (5) Building Officials and Code Administrators (BOCA).

The purpose of the building codes are to regulate the safe construction of

buildings.

Building survey: That portion of the pre-fire planning process that involves

the gathering of all the necessary information to develop a pre-fire plan of

a building or property.

C

Calorie: The amount of energy required to raise one gram of water 10C.

Carbonyl: The functional group with the structural formula -C-.

Carcinogen: A cancer-causing agent.

Chain: The way carbon atoms react with each other, producing covalent

bonds between them, resembling a chain with carbon atoms as the links.

Combustible liquids: Any liquid having a flash point temperature above

100 0F.

Combustion: A chemical reaction caused by oxidation that produces light

and heat. The production of light in the combustion process is the difference

between oxidation and combustion: Oxidation, regardless of slowness, will

give off heat but no light will be produced.

Common name: The name originally given to a compound upon its

discovery, prior to the adoption of an organized system of assigning proper

names.

Compressed gas: A gas that is under pressure, either still in the gaseous

state, or liquified.

Conduction: The transfer of heat through a medium.

Convection: The transfer of heat with a medium.

Cracking: The breaking of covalent bonds, usually between carbon atoms.

Critical pressure: The pressure required to liquify a gas at its critical

temperature.

Critical temperature: The temperature above which it is impossible to

liquify a gas.

Cryogenic gas: A gas with a boiling point of -1500F. or lower.

Cyclical: The structure of certain molecules where there is no end to the

carbon chain; the molecule is a closed structure resembling a ring, where

what would be the “last” carbon in the chain is bonded to the “first” carbon

in the chain. There are cyclical compounds in which the closed structure

contains the atoms of other elements in addition to carbon.

D

Derivative: A compound made from a hydrocarbon by substituting another

atom or group of atoms for one of the hydrogen atoms in the compound. “Di-“: The prefix that means two.

Diatomic: Two atoms, as in a diatomic molecule, which contains two atoms

bound covalently to each other.

Diffusion flame: The flame produced by the spontaneous mixture of fuel

vapors or gases and air.

Dry chemical: A term applied to an extinguishing agent suitable for use on

flammable liquids and electrical fires.

Dry-pipe sprinkler systems: A fire protection sprinkler system that has air

instead of water under pressure in its piping; dry systems are often installed

in areas subject to freezing.

Dry-pipe valve: A valve in a dry-pipe sprinkler system designed so that

moderate air pressure will hold back a much greater water pressure.

Dry powder: A term applied to the extinguishing agent suitable for use on

combustible metals.

E

Elevated storage system: A system of storing impounded water supplies

above the grade level at which the water will be used.

Emergency action plan: A written statement covering the actions employers

and employees must take to insure employee safety from fire and other

emergencies.

Endothermic: The absorption of heat.

Essential plant operations: Plant operations such as the monitoring of plant

power supplies, water supplies, and other essential services which cannot be

shut down for every emergency alarm. They may also include chemical or

manufacturing processes that must be shut down in stages or steps.

Ester: The hydrocarbon derivative with the general formula R-C-O-O-R’.

Ether: A hydrocarbon derivative with the general formula R-O-R1.

Evacuation warden: An employee designated to assist in the evacuation of

employees from the workplace.

Evaporation: The process by which molecules of a liquid escape through the

surface of the liquid into the air space above.

Exothermic: The liberation of heat.

Explosive range: The explosive range tells us that a certain mixture of fuel

vapor and air is required for the vapor to become ignitable. It is essentially

a concentration range for fuel in air, in which the vapors of a flammable

material will burn. The terms flammable limit and combustible limit are often

used to describe the explosive range. These three terms have identical

meaning and are interchangeable with each other. See lower explosion limit

and upper explosion limit.

Exposure: Property that may be endangered by a fire.

E

Fire brigade: An organization of industrial plant personnel who are trained

to use the fire fighting equipment and to carry out fire prevention activities

within the plant.

Fire brigade organization statement: A written statement, that identifies the

scope of the fire brigade, organizational structure, training requirements,

brigade size, and functions of the brigade members. Fire department connection: Connections provided at ground level through

which the fire department supplies sprinkler systems or standpipe systems.

Fire detection devices: The devices and connections installed in a building

for the purpose of detecting the presence of heat, smoke, and/or flame.

Fire door: A specially constructed, tested, and approved door installed for

the purpose of preventing the spread of fire.

Fire hazards: Conditions that are conducive to fire or are likely to increase

the extent or severity of fire. The terms hazard or hazardous are also used

to indicate the type of material or rate of burning.

Fire point temperature: The temperature a liquid must be before the

released vapor is in sufficient quantity to continue to burn, once ignited.

Fire prevention: Fire protection activities that deal with preventing fires

starting by eliminating fire hazards through inspection and education

programs.

Fire prevention code or ordinance: A law enacted in a political jurisdiction

for the purpose of enforcing fire prevention and safety regulations.

Fireproof: The word fireproof is a misnomer as it means that something

absolutely will not burn. Other terms such as fire resistive or fire resistant

should be used to indicate the degree of resistance to fire.

Fire protection engineer: A graduate of an accredited institution of higher

learning who has specialized in engineering problems related to fire

protection.

Fire pump: A water pump used in private fire protection for providing

additional water supply to installed fire protection systems.

Fire report: The official report of a fire, generally prepared by the person

in charge of the fire incident.

Fire resistive: Material and design of building construction meant to

withstand the maximum effect of a fire for a specific period of time.

Fire stream: A stream of water from a fire nozzle, used to control and

combat fires.

Fire tetrahedron: A four-sided, solid geometric figure that resembles a

pyramid, with one of the sides forming the base. Each side indicates one of

the four elements required to have fire.

Fire triangle: A plane geometric figure in which the three sides of an

equilateral triangle represent oxygen, heat, and fuel, the elements necessary

to sustain combustion.

Flammable liquids: Any liquid having a flash point temperature below

1000F.

Flashover: The stage of a fire in which a room or other confined area

becomes heated to the point that flames flash over the entire surface of the

area.

Flash point temperature: The lowest temperature a liquid may be and still

have the capability of liberating flammable vapor at a sufficient rate that,

when united with the proper amounts of air, the air-fuel mixture will flash

if a source of ignition is presented. The amounts of vapor being released at

the exact flash point temperature will not sustain the fire and, after flashing

across the liquid surface, the flame will go out. Foam: A sudslike extinguishing agent formed by mixing a foam-producing

compound with water. Mechanical foam is produced by agitation, chemical

foam is produced when two or more chemicals react.

Foam generators: Devices for mixing chemical or mechanical foam in

proper proportion with a stream of water to produce foam.

Fog stream: A water stream of finely divided particles used for fire control.

Frangible disc: A safety release device that will burst at a predetermined

pressure.

Free burning: The second phase of burning in which materials or structures

are burning in the presence of adequate oxygen.

Free radical: An atom or group of atoms bound together chemically with at

least one unpaired electron. A free radical is formed by the introduction of

energy to a covalently bonded molecule, when that molecule is broken apart

by the energy. It cannot exist free in nature and, therefore, must react

quickly with other free radicals present.

Freezing point: The temperature at which a liquid changes to a solid.

Fuel: Anything that will burn.

Functional Group: An atom or group of atoms, bound together chemically,

that has an unpaired electron, which when it attaches itself to the

hydrocarbon backbone, imparts special properties to the new compound thus

formed.

Fusible link: A connecting link device that fuses or melts when exposed to

heat. Used in sprinkler heads, fire doors, and ventilators.

Fusible plug: A safety relief device that will melt at a predetermined

temperature.

G

Gas: A state of matter defined as a fluid with a vapor pressure exceeding

40 psia at 100° F.

Gated wye: A hose appliance that has one female inlet and two or more male

outlets with a gate valve on each of the male outlets.

General formula: The general molecular formula for an analogous series of

compounds that will give the actual molecular formula for any member of the

series as long as the number of carbon atoms in the compound is known.

This number is substituted for the letter “n” in the formula.

Glycerol: A series of substituted hydrocarbons with three hydroxyl radicals

substituted for hydrogen atoms.

Glycol: A hydrocarbon derivative with two hydroxyl radicals substituted for

two hydrogen atoms.

Gravity tank: An aboveground water storage tank for fire protection and

water service. A water level of 100 feet provides a static pressure head of

43.3 psi minus friction loss in piping when water is flowing.

Grid system water mains: An interconnecting system of water mains in a

criss-cross or rectangular pattern.

H

H.A.D.(Heat Actuating Devices): Thermostatically controlled devices used

to activate fire equipment, alarms, or appliances.

Halide: A halogenated compound. Halogenated: A compound that has had a halogen atom substituted for

another hydrogen atom. A halogenated hydrocarbon is a hydrocarbon that

has had at least one hydrogen atom removed and replaced by a halogen.

Halogenation: The chemical reaction whereby a halogen is substituted for

another atom, usually a hydrogen atom.

Halogens: The elements of group VIIA: fluorine, chlorine, bromine, iodine,

and astatine.

HaIon: Halogenated extinguishing agent. Halon extinguishes fires by

inhibiting the chemical reaction of fuel and oxygen.

Handline: Small hoselines that can be handled and maneuvered without

mechanical assistance.

Heat: A form of energy; the total amount of vibration in a group of

molecules.

Heat transfer: The movement and dispersion of heat by conduction,

convection, or radiation.

Hose cabinet (rack): A recessed cabinet in a wall that contains a wall

hydrant and connected length of hose.

Hose clamp: A mechanical device for compressing fire hose to stop the flow

of water.

Hose reel: Cylinders around which fire hose may be manually or

mechanically rolled to keep it neat and orderly.

Hydrant hose house: A structure built around a yard hydrant containing fire

hose, nozzles, axes, and other fire fighting tools.

Hydrant wrench: A specially designed tool used to open or close a hydrant

and to remove hydrant caps.

Hydrocarbon: A covalent compound containing only hydrogen and carbon.

Hydrocarbon Backbone: The molecular fragment that remains after

hydrogen atom is removed from a hydrocarbon; the hydrocarbon portion of

a hydrocarbon derivative.

Hydrocarbon Derivative: A compound that began as a hydrocarbon, had a

hydrogen atom removed from the chain somewhere, and had functional

group attached to replace the hydrogen atom.

Hydroxyl: The functional group of the alcohols; the structural formula is

-O-H, usually written -OH.

I

Ignition continuity: The continuation of burning caused by the radiated heat

of the flame.

Ignition temperature: The exact minimum temperature that has the

capability of igniting a flammable vapor mixture.

Incipient stage fire: A fire in its beginning stage that can be controlled or

extinguished using portable fire extinguishers, Class II standpipe, or small

hose systems without the need for protective clothing or breathing

equipment.

Indirect application: A method of extinguishing fire by applying water fog

into a superheated atmosphere to obtain the maximum heat absorption and

steam generation for smothering and cooling the fire area.

Input heat: The amount of heat required to produce the evolution of vapors

from a solid or liquid.

Interior structural fire fighting: The act of fire suppression and rescue

inside buildings or enclosed structures where a fire has gone beyond the

incipient stage.

“Iso: The prefix (meaning the same) given to a compound having the same

number and kind of atoms as another compound, as in isomer.

Isomer: A compound with a molecular formula identical to another

compound but with a different structural formula. That is, a compound may

possess exactly the same elements, and exactly the same number of atoms of

those elements as another compound, but those atoms are arranged in a

different order from the first compound.

K

Ketone: A hydrocarbon derivative with the general formula R-C-R’.

Kinetic molecular theory: A theory that states all molecules are in constant

motion at all temperatures above absolute zero; molecules will move (or

vibrate) faster at higher temperatures because of the energy absorbed.

L

Latent heat of vaporization: The amount of heat a substance must absorb

when it changes from a liquid to a vapor or gas.

Liquid: A fluid with a vapor pressure no higher than 40 psia.

Liquified gas: A gas that has been converted to a liquid by pressure and/or

cooling.

Local alarm system: A combination of alarm components designed to detect

a fire and to transmit an alarm on the immediate premises.

Looped water main: A water main arranged in a complete circuit so water

will be supplied to a given point from more than one direction. Also called

a grid system.

Lower explosion limit (LEL) : The LEL is expressed as a percentage of the

total volume of the air-fuel mixture; it is the lowest concentration of vapor

fuel in air under which spontaneous combustion will occur. An example is

gasoline. A mixture containing 1.5% gasoline vapor in air (concentration of

air being 98.5% in this mixture) will spontaneously combust. The LEL in

this example is 1.5% or simply 1.5. Below this concentration, the mixture

is described as being too “lean”; or in other words, there is insufficient fuel

for spontaneous combustion to occur.

Melting point: The temperature at which a solid changes to a liquid.

Molecular formula: A method of representing a molecule by a written

formula, listing which atoms and how many of them are in the molecule,

without showing how they are bonded to each other.

“Mono-“: The prefix that means one.

Monomer: A simple, small molecule that has the special capability of

reacting with itself to form a giant molecule called a polymer.

N

“Neo-“: A prefix given to an isomer of another compound. It exists in

compounds that were named long ago and is used only when the compound

it best known by its common name. NFPA : National Fire Protection Association

“Normal”: The designation given to a straight-chain compound that has

isomers. The designation in the molecular formula is an “n-” in front of the

formula.

Q

Olefins: A synonym for the alkene series.

OS & Y Valve: A type of outside screw and yoke valve used on piping or

in pits connected to sprinkler systems. The position of the stem shows the

valve to be either open or closed.

Oxidation: The chemical combination of any substance with oxygen.

P

Paraffin series: An older name given to the alkanes.

Pendent sprinkler: An automatic sprinkler head designed for placement and

operation with the head pointing downward from the piping.

Peroxide: The hydrocarbon derivative with the general formula R-O-O-R’;

also the name of the peroxide radical which has the structural formula -0-0-.

Personal protective clothing: Clothing and equipment such as coat, boots,

pants, helmet, gloves, and breathing apparatus that shield the body from

heat, smoke, fumes, and other harmful conditions.

Phases of fire: A degree of flame progression. Phase I, fire in incipient

stage and beginning to grow. Phase II, freeburning, flame propagation is at

its greatest. Phase III, oxygen is deficient in the burn area, producing a

smoldering phase.

Phenyl: The general name for the radical of benzene.

Polymerization: The chemical reaction in which a special compound, called

a monomer, combines with itself to form a long-chain molecule called a

polymer.

Polymerize: The chemical reaction whereby a compound reacts with itself

to form a polymer.

Post indicator valve (PFV): A post-type valve that provides a visual means

of indicating “open” or “shut” position. It is found on the supply main of

installed fire protection systems.

Pre-action system: A type of automatic sprinkler system in which

thermostatic devices are employed to charge the system with water before

individual sprinkler heads are fused.

Pre-fire planning: The act of preparing to fight a fire in a particular building

or group of buildings by advance planning of possible fire fighting

operations.

Pressurized gas: A gas that is still in the gaseous state, but under higher

pressure than 14.7 psia.

Products-of-combustion: Materials given off or released during the burning

process.

Proper name: An agreed-upon system of naming organic compounds

according the longest carbon chain in the compound.

Proportioner: A device for inducing the correct amount of agent into

streams of water, especially for foam and wetting agents.

Proportioning: The occurrence of intermolecular collisions between oxygen and hydrocarbon molecules.

Proprietary system: A fire protection system that is owned and operated by

the owner of the property.

Pyrolysis: The breakdown of a molecule by heat.

E

Radiation: The transfer of heat with no medium.

Radiation heat: The transmission of heat through the medium of heat rays.

Radical: An atom or group of atoms bound together chemically that has one

or more unpaired electrons; it cannot exist in nature in that form, so it reacts

very fast with another radical present, to form a new compound; also known

as a “free” radical.

Rate-of-rise alarm system: One of the systems installed for detecting fire

by an abnormal rate of increase of heat; operates when a normal amount of

air in a pneumatic tube expands rapidly when heated and exerts pressure on

diaphragms.

Reducer couplings: Couplings with a large and small connector for

connecting hose couplings of two different sizes.

Remote alarm system: An alarm signaling system with a direct, privately

owned circuit that goes to a fire department into privately owned receiving

equipment.

Resonance: A phenomenon whereby a structure, to satisfy the rules of

covalent bonding, should be fluctuating (resonating) back and forth between

two alternate molecular structures, both of which are “correct” for the

molecule. It is a way of explaining what cannot be explained using only the

rules of covalent bonding.

Rope hose tool: A piece of rope spliced to form a loop through the eye of

a metal hook. Used for securing hose to ladders or other objects.

S

Saturated: A hydrocarbon possessing only single covalent bonds between

carbon atoms.

Siamese: A hose appliance that has two or more female inlets and one male

outlet; two or more inlets for one outlet.

Slopover: see also Boilover. Basically, the same principles that are

responsible for a boilover are the cause of a “slopover”. The fundamental

difference is that in a slopover the reaction is from water that has entered the

tank since the start of a fire. Usually this introduction is the result of the

firefighters’ activities as they attempt to extinguish the crude oil (or liquid of

similar characteristics) fire. A slopover will occur at some moment after the

heat wave has been formed – which may be from only a few minutes of

burning – and water or foam is being applied to the liquid surface. Either the

water from the hose streams or, after the bubbles collapse, the water in the

foam will sink into the oil, contacting the heat wave, where it is converted

to steam, and the agitation of the liquid surface spills some amount of oil

over the tank rim. Historically, slopovers, although still exposing the

firefighters to the danger of the escaping, burning oil, are not as violent as

are boilovers. Regardless of the term used to describe the occurrence – that

is, boilover, slopover, frothover, or whatever – the likelihood of some event that will cause the oil to cascade over the tank shell and down into the dike

area is always present when crude oil burns.

Solid stream: A hose stream that stays together as a solid mass, as opposed

to a fog or spray.

Spanner wrench: A tool used by firefighters for tightening or loosening

couplings.

Specific gravity: A measure of the weight of a material (liquid or solid) as

related to the weight of an equal volume of water.

Specific heat: The ratio between the amount of heat necessary to raise the

temperature of a substance and the amount of heat necessary to raise the

same weight of water the same number of degrees.

Sprinkler connection: A Siamese connection used by the fire department for

increasing the water supply and pressure to a sprinkler system.

STEL: Short Term Exposure Limit (STEL) refers to a safe level of exposure

(see also TLV) from inhalation for a continuous period of time that is short

(by OSHA standards either a 15 minutes or 5 minutes of continuous

exposure). The concentration established by the STEL (usually in ppm)

should not be exceeded during that period of exposure, and further, the time

limit of continuous exposure should not be exceeded, else there is a health

risk.

Straight chain: The configuration of the molecule of a hydrocarbon when

a carbon atom attaches itself to another carbon atom that has only one other

carbon atom already attached to it.

Structural effect: The effect upon certain properties of an analogous series

of compounds by branching. Properties such as boiling point, flash point,

ignition temperature, and others change as branches are added to compounds,

including isomers.

Structural formula: A drawing of the molecule, showing all the atoms of

the molecule and how they are bonded to each other atom.

Substituted: A compound that has had one or more of its atoms removed and

replaced by atoms of other elements in the molecule. A substituted

hydrocarbon is a compound that has had a hydrogen atom removed and

another atom substituted for it.

Synthesize: To make a molecule to duplicate a molecule made in nature.

1

“Tetra-“: The prefix that means four.

Thermal degradation: The term refers to the decomposition or degradation

of a material due to exposure to heat or energy. Materials can be thermally

degraded into three principal ways: anaerobic pyrolysis, oxidative pyrolysis

(“smoldering”), and flaming combustion.

TLV: The TLV or Threshold Limit Value refers to a safe level of exposure by

inhalation. The definition was established by the American Conference of

Governmental Hygienists. There are several variations or criteria levels for

the TLV. As an example, hydrogen sulfide has a TLV for short-term exposure

limits (STEL) of 15 minutes of only 5 ppm. Comparing this to the TLV-STEL

of 400 ppm for carbon monoxide provides an indication of the need to be

extremely careful when H2S is suspected. Under OSHA Standards, and particularly on MSDS (Material Safety Data Sheets) compounds are

associated with a time weighted average (TWA) TLV, which is the allowable

concentration for an 8-hour continuous exposure period. For firefighting

purposes, the short-term exposure is likely more realistic.

“Tri-“: The prefix that means three.

U

Unit: A molecular fragment that repeats itself in a series.

Unsaturated: A hydrocarbon with at least one multiple bond between two

carbon atoms somewhere in the molecule.

Upper explosion limit: The UEL is expressed as a percentage of the total

volume of the air-fuel mixture; it is the highest concentration of vapor fuel

in air under which spontaneous combustion will occur. An example is

gasoline. A mixture containing 7.6% gasoline vapor in air (concentration of

air being 92.4% in this mixture) will spontaneously combust. The UEL in

this example is 7.6% or simply 7.6. Above this concentration, the mixture

is described as being too “rich”; or in other words, there is too much fuel

and not enough oxygen for spontaneous combustion to occur.

V

Vapor density: A measurement of the weight of vapor compared to the

weight of air.

Vapor pressure: The pressure exerted by vapor molecules on the sides of

a container, at equilibrium.

Venting devices: A device that is designed to relieve excessive pressure

from the vapor space of a container. To accomplish this, the device will be

located on the tops of containers above the normal level of liquid of the full

tank. Some vents are installed to allow for the venting of the tank during

routine operations. Movement of liquid into or out of a container without the

space above the liquid level having the ability to breathe will result in

damage to the shell. Additional venting capacity is required to keep the

internal pressures at a safe level during fire emergencies. The various types

of venting devices in use include fusible plugs, spring-loaded relief valves,

pop-up-type hatch covers, pressure/vacuum vents, and weighted caps.

Vinyl: The general name for the radical of ethylene.

Volatilization: The changing of a liquid to a vapor.

W

Water solubility: A measure of the ability of a liquid to mix with water.

Weight effect: The change produced in certain properties, including flash

point, boiling point, and water solubility, as the molecular weight (calculated

by adding the atomic weights of all the atoms in the molecule) of compounds

in an analogous series is increased or decreased.

Wet-pipe sprinkler system: An automatic sprinkler system in which the

pipes are constantly filled with water under pressure.

Wet-standpipe system: A building standpipe system constantly filled with

water. Sections of small diameter fire hose are connected to the standpipe

system on each floor. Y

Yard hydrant: Similar to all other fire hydrants; they derive their name

from being located in the yard of an industrial complex and are installed for

private fire protection.