Glossary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Absorption
Additive
A liquid such as foam concentrates, emulsifiers, and hazardous vapor suppression liquids and foaming gents intended to be injected into the water stream at or above the water pressure.
Additive Proportioning
Additive proportioning is the method (such as premix, metered, or balanced pressure) used for the introduction of an additive or additive mixture at the recommended percent ratio into the water stream.
Adherence
See viscosity
Adhesion
The act of binding together substances of unlike compositions.
Aeration
The introduction of air into a foam solution to create bubbles that result in finished foam.
Air Aspirating Discharge Devices
These devices are specially designed to aspirate and mix air into the foam solution to generate foam. The foam then is discharged in a specific design pattern.
Alcohol-Resistant Foam Concentrate
This concentrate is used for fighting fires on water-soluble materials and other fuels destructive to regular AFFF or FFFP foams as well as for fires involving hydrocarbons. Alcohol-resistant foam concentrates are generally used in concentrations of 3% to 10% solutions depending on the nature of the hazard to be protected and the type of concentrate. This foam can also have film-forming and fluoroprotein characteristics on hydrocarbon fuels.
Anchor Point
A safe, secure area where a wildfire attack begins. The anchor point prevents the fire from outflanking the crew members and dangerously surrounding them.
Aqueous Film-Forming Foam (AFFF) Concentrate
This concentrate is based on fluorinated surfactants plus foam stabilizers and usually is diluted with water to a 1%, 3% or 6% solution. The foam formed acts as a barrier both to exclude air or oxygen and to develop an aqueous film on the fuel surface that is capable of suppressing the evolution of fuel vapors. The foam produced with AFFF concentrate is dry chemical compatible and thus is suitable for combined use with dry chemicals.
ARFF
Aircraft Rescue and Fire Fighting
Around-the-Pump Proportioner
The pressure drop between the discharge and suction side of the water pump of the system is used to induct foam concentrate into water by suitable variable or fixed orifices connected to a venturi inductor in a bypass between the pump suction and the pump discharge.
Aspirate
To draw in air; nozzle aspirating systems draw air into the nozzle to mix with the foam solution.
Authority Having Jurisdiction
The organization, office, or individual responsible for approving equipment, an installation, or a procedure.
Backdraft
Instantaneous explosion or rapid burning of su¬perheated gases that occurs when oxygen is introduced into an oxygen-depleted confined space. It may occur because of inadequate or improper ventilation procedures.
Backfire
Technique used in the indirect attack method for natural cover fires; intentionally setting a fire between the control line and the advancing fire. The intent is for the backfire to meet the advanc¬ing fire some distance from the control line.
Back Pressure
Pressure loss or gain created by changes in elÂevation between the nozzle and pump.
Bank-Down Method
This method of foam application may be employed when an elevated object is near or within the area.
Batch Mix
Manual addition of foam concentrate to a water storage container or tank to make foam solution.
Batch-Mixing
The making of foam solution by pouring an appropriate amount of foam concentrate into the water tank.
Biodegradable
Capable of being broken down into innocuous products by the action of living things, such as microorganisms.
Blanket
A layer of foam.
BLEVE
Acronym for Boiling Liquid Expanding Vapor Explosion.
Boil over
Overflow of crude oil from its container when the heat wave reaches the water level in the tank the water flashes to steam causing a violent expulsion of the material as a froth.
British Thermal Unit (Btu)
The amount of heat needed to raise the temperature of one pound of water one degree Fahrenheit.
Bubble
The building block of foam composed of a film of fluid enclosing a volume of air. Bubble characteristics of water's content and durability influence foam performance.
Burn back Resistance
The ability of a foam blanket to resist direct flame impingement such as would be evident ii a partially extinguished petroleum fire.
Chemical Foams
Foams produced as a result of a reaction between two chemicals.
Class A Fire
A fire in ordinary combustible materials, such as vegetation, wood, cloth, paper, rubber, and many plastics.
Class A Foam
Foam intended for use on Class A fires. An aggregation of bubbles having a lower density than water. The foam bubbles and the solution draining from them attach to and penetrate Class A fuels due to the reduced surface tension imparted to the water by the foam concentrate. The bubbles hold moisture and release it as the foam breaks down, prolonging the time the moisture may be absorbed by the fuels. When applied in adequate quantities, the foam acts to exclude air from the fuel-air interface, envelope combustible vapors and resist disruption due to wind, heat and flame.
Class B Fire
Fires in flammable liquids, combustible liquids, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, alcohols, and flammable gases.
Class B Foam
Foam intended for use on Class B fires. An aggregation of bubbles of lower density than oil or water that exhibits a tenacity for covering horizontal surfaces. It flows freely over a burning liquid surface and forms a tough, air-excluding, continuous blanket that seals volatile combustible vapors from access to air. It resists disruption from wind and draft or heat and flame attack and is capable of resealing in case of mechanical rupture. Fire Fighting foams retain these properties for relatively long periods of time.
Class C Fire
Fires that involve energized electrical equipment. When electrical equipment is de-energized, the fire might continue to burn as a Class A, Class B, or Class D fire.
Class D Fire
Fires in combustible metals, such as magnesium, titanium, zirconium, sodium, and potassium.
Cohesion
The act of binding together substances of like composition.
Combination Nozzle
Also called an "adjustable fog nozzle." This nozzle is designed to provide either a solid stream or, fixed spray pattern suitable for water or wet water application.
Combustible Liquid
Liquid having a flash point at or above 100°F ;37.8°C) and below 200°F (93.3°C).
Compressed Air Foam System (CAFS)
A foam system that combines air under pressure with foam solution to create foam in the hose or mixing chamber. A CAFS consists of a pressurized air source, water pump, means to apply the foam (hose, nozzle, turret, etc.) and source of foam solution.
Concentrate
A substance that has been concentrated; specifically a liquid that has been made denser, as by the removal of some of its water.
Conduction
Transfer of heat energy from one body to another through a solid medium.
Conductivity
The ability of a substance to conduct an electrical current.
Confinement
1) The process of controlling the flow of a spill and capturing it at some specified location. (2) fire fighting operations required to prevent fire from extending to uninvolved areas or strucÂtures.
Consistency
Uniformity and size of bubbles.
Containment
The act of stopping the further release of a mateÂrial from its container.
Convection
Transfer of heat by the movement of fluids or gases; usually in an upward direction.
Cooling
The act of lowering the temperature of the fuel and adjacent surfaces.
Corrosives
Those materials that cause harm to living organÂisms by destroying body tissue.
Degradation
The act of degrading or being degraded in rank, status, or condition.
Density
Weight per unit of volume of a substance. The density of any substance is obtained by dividing the weight by the volume. The amount of foam solution in the foam (note difference from "expansion").
Diked Areas
Areas that are bounded by either natural or manmade barriers intended to keep spilled fuel within these boundaries.
Direct Attack
Firefighting operations involving the application of extinguishing agents directly onto the burning fuel. (1) To attack a natural cover fire directly at or close to the burning edge. (2) Application of a fire stream directly onto a burning fuel.
Drainage Dropout Rate
See Drain Time.
Drainage Rate
See Drain Time.
Drain Time
The amount of time it takes foam to break down. Also called Drainage Rate and Drainage Dropout Rate. The time (minutes) it takes for foam solution to drop out from the foam mass for a specified percent of the total solution contained in the foam to revert to liquid and drain out of the bubble structure
Dry Foam
Foam that has a very high air-to-foam solution ratio. This foam will cling to horizontal surfaces.
Durability
The effective life span of foam bubbles.
Eductor
A device that uses the Venturi principle to introduce a proportionate quantity of foam concentrate into a water system. The pressure at the throat is below atmospheric pressure, allowing concentrate at atmospheric pressure in storage to flow into the water stream.
Ejector
Occasionally an injector is used to proportion mixes; this type of equipment is frequently referred to as in "ejector," though sometimes as an "injector."
Envelopment
Attacking key or critical segments around the entire fire perimeter at the same time.
Expansion
See Aeration.
Expansion Ratio
See Flammable Limit.
Explosive Limit
See Flammable Range.
Explosive Range
See Flammable Range.
Exposure Protection
Application of an agent to uninvolved areas to limit absorption of heat to a level that will minimize damage and prevent ignition, whether the source of heat is external or internal. Covering any object in the immediate vicinity of the fire with water or foam.
Film-Forming Fluoroprotein Foam Concentrate (FFFP)
This concentrate uses fluorinated surfactants to produce a fluid aqueous film for suppressing hydrocarbon fuel vapors. This type of foam utilizes a protein base plus stabilizing additives and inhibitors to protect against freezing, corrosion, and bacterial decomposition, and it also resists fuel pick-up. The foam is usually diluted with water to a 3% or 6% solution and is dry chemical compatible.
Fire Flow
(1) Quantity of water available for fire fighting in a given area. It is calculated in addition to the normal water consumption in the area. (2) The amount of water required to extinguish a fire in a timely manner.
Fire Point
Temperature at which a liquid fuel produces sufficient vapors to support combustion once the fuel is ignited. The fire point is usually a few degrees above the flash point. Also called Burning Point.
Fire Retardant
Any substance that by chemical or physical action reduces the flammability of combustibles.
Fire Tetrahedron
Model of the four elements required to have a fire. The four sides represent fuel, heat, oxygen, and chemical chain reaction.
Fire Triangle
Plane geometric figure in which the three sides of an equilateral triangle represent oxygen, heat and fuel the elements necessary to sustain combustion.
Flammable Limit
Percentage of a substance in air that will burn once it is ignited. Most substances have an upper (too rich) and lower (too lean) flammable limit Also called Explosive Limit.
Flammable Liquid
A liquid that has a closed-cup flash point that is below 37.8°C (100°F) and a maximum vapor pressure of 2068 mm Hg (40 psia) at 37.8°C (100°F).
Flammable Range
The range between the upper flammable limit and lower flammable limit in which a substance can be ignited. Also called Explosive Range.
Flank
Sides of a natural cover fire.
Flanking
Attacking the sides of the fire from a less active area or from an anchor point; the intent being to have the two crews attacking the flanks meet at the head of the fire.
Flashover
Stage of a fire at which all surfaces and object within a space have been heated to their ignition temperature and flame breaks out almost at once over the surface of all objects in the space.
Flash Point
Minimum temperature at which a liquid gives off enough vapors to form an ignitable mixture with air near the liquid's surface.
Fluid Foam
A shaving cream like foam that will hold peaks and cling to vertical surfaces. Used for protection of fuels
Foam
A stable aggregation of small bubbles of lower density than oil or water that exhibits a tenacity for covering horizontal surfaces.
Foam Application Rate
The amount of foam solution in liters or gallons per minute expressed as a relationship with a unit of area, usually square meter or square foot.
Foam Blanket
A covering of foam over the surface of combustible materials or flammable liquids to provide extinguishment and/or prevent ignition.
Foam Burn Back Resistance
The ability of a foam blanket to retain aerated moisture and resist destruction by heat and flame.
Foam Chemicals
A generic name for the liquid foam concentrate, foam solution, and foam in whatever form it is being used.
Foam Concentrate
The foaming agent as received from the supplier that, when mixed with water, becomes foam solution.
Foam Concentrate Type
A classification of a foam concentrate that includes chemical composition as defined under foam concentrate, including use percentage, the minimum usable temperature, and the fuels on which the concentrate is effective.
Foam Discharge Device
Any device that, when fed with a foam-water solution, produces foam. These devices shall be permitted to be non-air-aspirating (e.g., sprinklers, water nozzles) or air-aspirating (e.g. foam-water sprinklers, directional foam-water nozzles, foam nozzles). All discharge devices have a special pattern of distribution peculiar to the particular device.
Foam Drain Time
The foam drain time, commonly the 25% drainage time, is the time required for 25 percent of the original foam solution (foam concentrate plus water) to drain out of the foam.
Foam Expansion
The ratio between the volume of foam produced and the volume of solution used in its production.
Foam Generation
The foam production process of solution agitation in a hose, mix chamber, or nozzle.
Foam Generators - Aspirator Type
Foam generators, fixed or portable, n which jet streams of foam solution aspirate sufficient amounts of air that is then entrained on the screens to produce foam, and which usually produce foam with expansion ratios of not more than 250:1.
Foam Generators-Blower Type
Foam generators can be fixed or portable. The foam solution is discharged as a spray onto screens through which an airstream developed by a foam or blower is passing. The blower can be powered by electric motors, internal combustion engines, air, gas, or hydraulic motors or water motors. The water motors are usually powered by foam solution.
Foam Line
A body of foam placed along areas to be protected from fire; also used as an anchor for indirect attack in place of hand-made fire trail.
Foam Monitor Stream
A large capacity foam stream from a nozzle that is supported in position and can be directed by one person.
Foam Nozzle
A specially designed hose line nozzle designed to aspirate air that is connected to a supply of foam solution.
Foam Pattern
The ground area over which foam is distributed during the discharge of a foam-making device.
Foam Proportioner
Device that injects the correct amount of foam concentrate into the water stream to make the foam solution
Foam Proportioning System
The apparatus and techniques used to mix concentrate with water to make foam solution.
Foam Solution
(1) A homogeneous mixture of water and foam conÂcentrate in a proportion that meets the needs of the user. The dilute working-form of foam concentrate to which air is added to produce foam. (2) Mixture of foam concentrate and water after it leaves the proportioner but before it is discharged from the nozzle and air is added to it.
Foam Stability
The relative ability of a foam to withstand sponÂtaneous collapse or breakdown from external causes.
Foam Systems
The apparatus and techniques used to mix conÂcentrate with water to make solution, pump and mix air and solution to make foam, and transport and eject foam. (Systems defined here include compressed air foam and nozzle aspirated.)
Foam Tetrahedron
Model of the four elements required to create foam. The four sides represent water, foam concentrate, air and agitation.
Foam Type
A combined measure of drain time and expansion to describe durability, consistency, viscosity, and density.
Frontal Attack
Where the crew begins the attack from an anchor point at or near the head of the fire and then proceeds to the flanks.
Gpm
Gallons per minute.
Heat Resistance
Foam's ability to resist the actual heat of the liquid or surface on which it is applied.
High Expansion Foam
A device or system that adds the energy of a pressurized air source to the energy of a pressurized water source to create foam.
High-Energy Foam Systems
A homogeneous foam concentrate and water mixture, in the mix ratio required to meet the needs of the user, to which air is added to produce foam.
Homogeneous
A substance having uniform structure or composition throughout.
Hot-Smoldering Phase
Phase of combustion when the level of oxygen in a confined space is below that needed for flaming combustion. The hot smoldering phase is characterized by glowing embers, high heat at all levels of the room, and heavy smoke and fire gas production.
Hydrocarbon
Organic compound containing only hydrogen and carbon and found primarily in petroleum products and coal.
Hydrolyze
A chemical process of decomposition involving splitting of a bond and the addition of the elements of water.
Handline Nozzle
Any nozzle that can be safely handled by one to three firefighters and flows less than 350 gpm.
Incipient Phase
First phase of the burning process where the substance being oxidized is producing some heat, but the heat has not spread to other substances nearby. During this phase, the oxygen content of the air has not been significantly reduced.
Indirect Attack
(1)Firefighting operations involving the application of extinguishing agents to reduce the buildup of heat released from a fire within a structure without applying the agent directly onto the burning fuel. (2) Directing the fire stream at the ceiling level to generate steam. The steam helps darken the fire and cool the area enough so that firefighters may safely enter and make a direct attack to extinguish the fire. (3) A method of controlling a wildfire where a control line is constructed or located some distance from the edge of the main fire.
Inductor
A control mechanism that allows a regulated quantity of foam concentrate to be introduced into the main hose line.
Ingestion
To take things into the body (food, drugs, etc.) by swallowing.
Ingredient
Each chemical component used in the formulation of a product.
Intergranular Corrosion
A corrosive attack on metal at the grain boundary.
LC50
The concentration at which 50% of test animals die within a specified time frame.
LEL
Abbreviation for Lower Explosive Limit.
LD50
The dosage at which 50% of test animals die within a specified time frame.
Listed
Equipment, materials, or services included in a list published by an organization that is acceptable to the authority having jurisdiction and concerned with evaluation of products or services, that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services, and whose listing states that either the equipment, material, or services meets appropriate designated standards or has been tested and found suitable for a specified purpose.
Low Energy Foam System
A device or system that uses only energy produced by the velocity of the water stream to create foam.
Low Expansion Foam
Foams with expansion ratios up to 20:1.
Manual Regulation
A proportioning method or device that requires a manual adjustment to maintain a desired mix ratio over a changing range of water flows and pressures.
Mechanical Foams
Foams produced by a physical agitation of a mixture of water, air, and a foaming agent.
Medium Expansion Foam
Foams with expansion ratios ranging from 20:1 to 200:1.
Metered Proportioning
A separate foam concentrate pump is used to inject foam concentrate into the water stream. Orifices or venturis, or both, control or measure the proportion of water to foam concentrate. Either manual or automatic adjustment of foam concentrate injection by pressure or flow control can be utilized. Another type of proportioning uses a pump or diaphragm tank to balance the pressure of the water and the concentrate. Variable orifices proportion automatically through a wide range of solution requirements.
MIL-SPEC Foams
Foams that meet military specifications.
Miscibility
The property of being capable of mixing in any ratio without separation of two phases.
Mix Ratio
The ratio of liquid foam concentrate to water, usually expressed as a percent.
Mixed Solution
The combination of water and foam concentrate used to prodvuce the foam used for fire suppression.
Mixing Chamber
A tube drilled, with deflectors or baffles, that produces tiny, uniform bubbles in a short distance (1 to 2 feet).
Monitor
A turret-type nozzle usually mounted on an engine.
MSDS
Acronym for Material Safety Data Sheet.
Nozzle Aspirated Foam System (NAFS)
A foam generating device that mixes air at atmospheric pressure with foam solution in a nozzle chamber.
Overhaul/Mop-Up
The final stages of fire control, following suppression of the main body of fire, during which smoke conditions and visibility gradually improve, and pockets of fire are sought out to complete extinguishment.
Oxidation
Chemical reaction in which oxygen combine; with other substances. Fire, explosions, and rusting are examples of oxidation.
Oxidizer
Substance that yields oxygen readily and may stimulate the combustion of organic and inorganic matter.
Polar Solvents
Flammable liquids that have an attraction for water, much like a positive magnetic pole attracts a negative pole; examples include alcohols, ketones, and lacquers.
Positive Heat Balance
When heat is fed back to the fuel. A positive heat balance is required to maintain combustion.
Premixing
Mixing pre measured portions of water and foam concentrate in a container. Typically, the premix method is used with portable extinguishers
Proportioner
Pumps foam concentrate, as demanded, into the hose line.
Proportioning
The mixing of water with an appropriate amount of foam concentrate to form a foam solution.
Protein Foam Concentrate
A concentrate consisting primarily of products from a protein hydrolysate, plus stabilizing additives and inhibitors to protect against freezing, to prevent corrosion of equipment and containers, to resist bacterial decomposition, to control viscosity, and otherwise to ensure readiness for use under emergency conditions. They are diluted with water to form 3% to 6% solutions depending on the type. These concentrates are compatible with certain dry chemicals.
Pyrolysis
Chemical decomposition caused by heat that gen¬erally results in the lowered ignition tempera¬ture of the material.
Quarter Drain Time
See Quarter Life.
Quarter-Life
The time required in minutes for one-fourth of the total liquid solution to drain from a foam blanket. Also called 25 Percent Drain Time and Quarter Drain Time.
Radiation
Transfer of heat energy through light by electro¬magnetic waves. Also called Radiated Heat.
Radiative Feedback
Radiant heat providing energy for continued vaporization.
Rain-Down Method
This method of foam application directs the stream into the air above the fire and allows the foam to float gently down onto the surface of the fuel.
Rate Of Vaporization
The speed at which a liquid evaporates or vaporizes.
Refractometer
A device used to measure the amount of foam concentrate in the solution. This device operates in the principle of measuring the velocity of light that travels through the foam solution.
Resistance to Freezing
A foam concentrate's usefulness after it has frozen and thawed. Some concentrates freeze at lower temperatures than others; most can be used after freezing and thawing.
Retention
The characteristic of Class A foam and foam solution to remain on and in the fuel, reduce the fuel temperature, and increase the fuel moisture content.
Roll-On Method
This method of foam application directs the foam stream on the ground near the front edge of the liquid pool on fire. The foam then rolls across the surface of the fuel.
Rollover
Unburned combustible gases released during the incipient or early steady-state phase accumulate at the ceiling level. These superheated gases are pushed, under pressure, away from the fire area and into uninvolved areas where they mix with oxygen. When their flammable range is reached, they ignite and a fire front develops, expanding very rapidly and rolling over the ceiling.
Scrubbing
The process of agitating foam solution and air within a confined space (usually a hose) that produces tiny, uniform bubbles - the length and type of hose determine the amount of scrubbing and, therefore, foam quality.
Semi subsurface Injection
A system that discharges the foam through a flexible hose that rises from the bottom of the tank, up through the fuel, to the surface.
Separating
The act of creating a barrier between the fuel and the fire.
Shall
Indicates a mandatory requirement.
Short-Term Retardant
A viscous, water-based substance wherein water is the fire suppressing agent.
Should
Indicates a recommendation or that which is advised but not required.
Size-Up
Mental evaluation made by the operational officer in charge that enables him or her to determine a course of action to accomplish the mission; a mental process of evaluating all influencing factors before committing personnel and equipment to a course of action. Size-up includes such factors as time, location, nature of occupancy, life hazard, exposures, property involved, nature and extent of fire, weather, and fire fighting facilities.
Slug Flow
In CAFS only, when foam solution is not rich enough to mix with air, inadequate mixing occurs; this sends pockets (or plugs) of water and air to the nozzle.
Solubility
Degree to which a solid, liquid, or gas dissolves in a solvent (usually water).
Specific Gravity
Weight of a substance compared to the weight of water
Stability
See Viscosity.
Standard
A document, the main text of which contains only mandatory provisions using the word "shall" to indicate requirements and which is in a form generally suitable for mandatory reference by another standard or code or for adoption into law. Nonmandatory provisions shall be located in an appendix or annex, footnote, or fine-print note and are not to be considered a part of the requirements of a standard.
Standard Cubic Feet per Minute (SCFM)
An expression of air flow rate in which the air flow rate is corrected to standard temperature and pressure. The metric conversion is shown as SCMS (Standard Cubic Meters per Second).
Static Source
Body of water that is not under pressure or in a supply piping system and must be drafted from in order to be used. Static sources include ponds, lakes, rivers, wells, and so on.
Steady-State Burning Phase
Generally considered the phase of the fire where sufficient oxygen and fuel are available for fire growth and open burning to a point where total involvement is possible.
Structure Fire
Fire that involves a building, enclosed structure, or like property.
Subsurface Injection
A process by which foam is pumped into the bottom of a burning petroleum tank and allowed to float to the top to form a fire extinguishing blanket.
Suppressing
Sometimes referred to as smothering. The act of preventing the release of flammable vapors and therefore reducing the possibility of ignition or reignition.
Suppressant
An agent used to extinguish the flaming and flowing phases of combustion by direct application to the burning fuel.
Surface Tension
The elastic-like force in the surface of a liquid, tending to minimize the surface area and causing drops to form. (Expressed as Newton's per meter or dynes per centimeter; there are 1,000,000 dynes per Newton.)
Surface-To-Mass Ratio
The ratio of the surface area of the fuel to the mass of the fuel.
Surfactant
(1) A chemical that lowers the surface tension of a liquid. ( 2) A surface active agent; any wetting agent.
Surge
The sudden decompression of a discharge line caused by the rapid opening of the discharge appliance.
Synthetic Foam Concentrate
Synthetic-foam concentrate is based on foaming agents other than hydrolyzed proteins and includes Aqueous Film-Forming Foam (AFFF) concentrates, medium and high expansion foam concentrates, and other synthetic foam concentrates.
Training Concentrates
Foam concentrates that are designed especially for training. They are specifically formulated for hydrocarbon fuel fire training. Training concentrates generally reproduce the white color, appearance, expansion ratio, and drain time of Class B foam.
Tube Seal
A type of seal used on a floating roof fuel storage tank. The seal is constructed of urethane foam that is contained within an envelope. The seal connected to the edge of the roof around the entire circumference of the tank. A secondary weather shield is usually installed above this main seal.
Turret
Large master stream appliance mounted on a pumper or trailer and connected directly to a pump. Also called Deck Gun or Deck Pipe.
Twenty Five (25) Percent Drain Time
See Quarter-Life.
UEL
Abbreviation for Upper Explosive Limit.
Uniform Corrosion
Removal of metal by chemical means over the entire surface.
Use Level
The appropriate ratio of liquid foam concentrate to water recommended by the chemical manufacturer for each class of fire.
Vapor Density
Weight of a given volume of pure vapor or gas compared to the weight of an equal volume of air at the same temperature and pressure. Vapor density less than 1 indicates a vapor lighter than air; a vapor density greater than 1 indicate a vapor heavier than air.
Vaporization
Passage from a liquid to a gaseous state. Rate of vaporization depends on the substance involved heat, and pressure.
Vapor Suppression
The action taken to reduce the emission of vapor at a fuel spill.
Variable
See Automatic.
Venturi
When a fluid is forced under pressure through a restricted orifice, there is a decrease in the pressure exerted against the side of the constriction. Because the surrounding air is under greater pressure, it rushes into the area of lower pressure.
Viscosity
(1) A liquid's thickness or ability to flow. (2) An indication in the ability of the foam to spread and cling, as well as to cling to itself, upon delivery.
Volatility
The ability of a substance to vaporize easily at a relatively low temperature.
Water, Artificial Sea
A solution that consists of 1.10% magnesium chloride hexahydrate, 0.16% calcium chloride dihydrate, 0.40% anhydrous sodium sulfate, 2.5% sodium chloride, and 95.84% deionized or distilled water.
Water, fresh
Deionized or distilled water to which 140 ppm of calcium chloride have been added.
Water Retention
A foam's ability to retain its water content.
Wet Water
Water with added chemicals, called wetting agents, that increase water's spreading and penetrating properties due to a reduction in surface tension.
Wetting Ability
The ability of solution to penetrate and soak into a solid.
Wetting Agent
A chemical added to water to reduce surface tension, allowing the solution to spread and penetrate more effectively than water alone.
Wildfire
An unplanned, unwanted, and uncontrolled fire involving vegetative fuels that often threatens structures.
Wildfire Mop-up
See Wildfire Overhaul.
Wildfire Overhaul
Operations involving extinguishing hot spots and hidden fires after the main body of fire has been knocked down. Also known as Mop-Up.