FAQs FIRE FIGHTING

Glossary

A list of terms commonly used in the the fire fighting foam industry and what they mean.

Aeration

The introduction (or entraining) of air into a foam solution to create bubbles that result in finished foam.

AFFF

See Aqueous Film-Forming Foam.

Alcohol Resistant (AR)

A foam concentrate for use on polar solvents in addition to hydrocarbons.

Alcohol Resistant Aqueous Film- Forming Foam (AR-AFFF)

AFFF that is suitable for use on polar solvents in addition to hydrocarbons.

Alcohol Resistant Film-Forming FluoroProtein (AR-FFFP)

FFFP that is suitable for use on polar solvents in addition to hydrocarbons.

Application Rate

The rate at which foam solution is applied to a fire. Expressed as litres of foam solution per square metre of fire area per minute (l/m²/min) - typically between 4 and 10 l/m²/min.

Application Time

The duration of time over which foam is applied.

Approval

Certificate that ensures a foam concentrate meets the requirements of a foam Standard.

Aquatic Toxicity

A measure of how poisonous foam is to creatures living in the water environment.

Aqueous Film-Forming Foam (AFFF)

A synthetic foam concentrate containing detergent and fluorocarbon surfactant. Forms a foam capable of producing a vapour-suppressing aqueous film on the surface of some hydrocarbon fuels. Provides rapid flame knockdown on short preburn, shallow spill fires (eg. aircraft crash fires), but not suited for use on long pre-burn, deep-seated fires (eg. storage tank fires). 

AR

See Alcohol Resistant.

AR-AFFF

See Alcohol Resistant Aqueous Film-Forming Foam.

AR-FFFP

See Alcohol Resistant Film-Forming FluoroProtein.

Aspirated Foam

Foam blanket obtained by mixing water, foam concentrate, and air. Expansion ratio typically 2:1 or more. Also called Finished or Expanded Foam.

AVGAS

Aviation gasoline. Similar to gasoline used in cars except that AVGAS has a higher octane rating.

Avtur

Aviation kerosene.

Backboard

Metal sheet attached to back of test fire tray that enables foam to be applied gently on to a fire. Particularly important for Alcohol Resistant foams.

Balanced Pressure Proportioner (BPP)

A foam concentrate proportioning system designed to inject automatically the correct quantity of foam concentrate into a water stream over wide flow and pressure ranges by balancing the pressure of a foam concentrate with that of the water supply. Used in combination with a bladder tank or balance valve.

Balance Valve

A device that controls the flow of foam concentrate into a BPP at a pressure that is balanced to water line pressure.

Biodegradable

Capable of being broken down into innocuous products by the action of living creatures such as micro-organisms.

BPP

Balanced Pressure Proportioner.

British Standards Institute (BSI)

An independent national organisation that facilitates the production of standards, tests products, and assesses organisations against the national standard for quality management systems BS EN ISO 9001 : 2000. A member of ISO. Publishes BS 5306: Section 6.1:1988 Specification for Low Expansion Foam Systems.

Bund

An area surrounding a storage tank which is designed to contain the liquid product in the event of a tank rupture. Also referred to as Dike.

Burnback Resistance

The ability of a foam blanket to resist direct flame and heat impingement such as would be evident in a partially extinguished fire.

CAFS

Compressed-Air Foam System.

CFR

Crash, Fire and Rescue.

Civil Aviation Authority (CAA)

Organisation responsibile for civil aviation.

Unleaded Gasoline (ULG)

Gasoline in which lead has been replaced with, for example, an oxygenate such as MTBE.

PFOS

Perfluorooctanesulfonic acid. A man-made fluorosurfactant used in the manufacture of Fire Fighting Foam until 2005 when it was discovered to be toxic, bioaccumulative and very persistent in the environment. Classified as a persistent organic pollutant in 2009.

Class A Fire

A fire in materials such as wood and paper where the cooling effect of water is of paramount importance in extinguishing the risk (CEN definition). Fires which occur in ordinary combustible materials, ie. wood, paper, rubber, and certain plastics, etc. (NFPA 10 definition).

Class A Foam

Specially formulated for use on Class A fires. Essentially wetting agents that reduce the surface tension of water and allow it to soak into combustible materials easier than plain water.

Class B Fire

A fire involving a flammable liquid where a blanket or smothering effect is of first importance in extinguishment (CEN definition). Fires which occur in flammable liquids, oils, tars, lacquers, etc. and flammable gases (NFPA 10 definition). Fires in flammable and combustible liquids, gases, and greases (UL 162 definition).

Class B Foam

Foam formulated to be used on fires or spills of flammable and combustible liquids.

Class C Fire

Fires involving gases or liquefied gases in the form of a liquid spillage, or a liquid or gas leak (CEN definition). Fires involving energised electrical equipment where the electrical non-conductivity of the extinguishing agent is particularly important (NFPA 10 definition).

Class D Fire

A fire involving a metal such as magnesium, sodium, lithium, and potassium, etc (CEN definition). Fires which occur in metals such as magnesium, zirconium, lithium and potassium, etc. (NFPA 10 definition).

Control

A reduction in fire intensity of approximately 90 percent.

Critical Application Rate (CAR)

The minimum rate at which foam solution needs to be applied to a fire in order to achieve extinguishment.

CEN

Comite Europeen de Normalisation (French) or European Committee for Standardization (English).  Brussels-based association of national standards bodies from the eighteen member countries of the European Union (EU) and the European Free Trade Association (EFTA). Currently drafting four new foam standards for low expansion foam on hydrocarbons, low expansion foam on polar solvents, medium expansion foam, and high expansion foam.

Combustible Liquid

Liquid having a flash point at or above 37.8C (100F).

Det Norske Veritas (DNV)

The Norwegian Testing House. An independent foundation with the object of safeguarding life and property at sea and ashore. Approves foam concentrates and foam equipment.

Dike

See Bund.

Discharge Device

A fixed, semi-fixed, mobile, or portable device that directs the flow of foam on to a fire.

DIN

Deutsches Institut fur Normung. The German national standards body. Coordinates and publishes standards governing foam concentrate performance.

DNV

See Det Norske Veritas. Drainage Time (DT): The time required in minutes for 25% (usually) or 50% of the total foam solution to drain from aspirated foam. A method of measuring foam stability. Also referred to as drainage Rate.

EC50

The Effective Concentration in water of a material such as foam concentrate that would produce a particular response in 50% of a test batch of animals (eg. Immobilisation of Daphnia) or a 50% reduction in a particular response (eg. Inhibition of the growth of algae).

Eductor

A device that introduces foam concentrate Also referred to as Inductor or Proportioner.

Eduction Rate

The percentage of foam concentrate mixed or introduced into the water supply line to produce foam solution. Also called Induction Rate or Proportioning Rate or Pick-Up Rate.

Expanded Foam

Foam blanket obtained by mixing water, foam concentrate, and air. Expansion ratio typically 2:1 or more. Also referred to as Aspirated Foam or Finished Foam.

Expansion Ratio (ER)

The ratio of final foam volume to original foam solution volume before adding air.

Extinction Time (ET)

The time taken by foam to extinguish a fire.

F3

Fluorine free foam. Also known as FFF.

Factory Mutual International (FMI)

The US industrial and commercial property insurer specialising in loss prevention engineering and risk management services. Internationally recognized as an approved testing body for loss prevention, equipment, materials, and services. Approves foam concentrates and foam equipment.

FDA

See Foam Destroying Action.

Federal Aviation Administration (FAA)

The US authority responsible for civil aviation.

FFF

Fluorine-Free Foam. Also known as F3.

FFFP

See Film-Forming FluoroProtein.

Film-Forming

A foam concentrate containing fluorocarbon surfactants that has a spreading coefficient greater than zero and so forms a foam capable of producing a vapour-suppressing aqueous film on the surface of some hydrocarbon.

Wicking Effect

Occurs when non-aspirated AFFF applied to unignited spillage of low volatility/high flash point fuels (eg. aviation kerosene) causes fuel to ignite more readily.

PFOA

Perfluorooctanoic acid. PFOA has been discovered to be an unintentional byproduct of the telomer manufacturing process used in the production of fluorosurfactants. A man-made chemical with a carbon chain length of C7, PFOA was first synthesised in 1947. It is toxic, bioaccumulative and very persistent and has been found at very low levels in the environment and in the blood of the general population since 1960. PFOA has also been shown to cause adverse effects in laboratory animals.

Film-Forming FluoroProtein (FFFP)

A natural protein-based foam concentrate containing fluorocarbon surfactants that forms a foam capable of producing a vapour-suppressing aqueous film on the surface of hydrocarbon fuels. Developed in the 1980s. Combines rapid knockdown of top quality AFFF with high post-fire security and low environmental impact of top quality FP.

Finished Foam

Foam blanket obtained by mixing water, foam concentrate, and air. Expansion ratio typically 2:1 or more. Also referred to as Aspirated Foam or Expanded Foam.

Fixed System

Complete installation that generates aspirated foam and discharges it.

Flame Transmission

Faint flames that flicker over the surface of an AFFF foam blanket. If the foam blanket does not completely cover the fuel, the flames may ignite exposed fuel. Also referred to as AFFF Ghosting Effect.

Flammable Liquid

Any liquid having a flash point below 37.8C (100F).

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 Range

The range between the upper flammable limit and lower flammable limit in which a substance can be ignited. Also called Explosive Range.

Flashback

Reignition of flammable liquid caused by exposure of its vapours to a source of ignition such as a hot metal surface or a spark.

Flash Point

The lowest temperature at which a flame can propogate in the vapours above a liquid.

Fluororocarbon Surfactant

Fluorocarbon surface active agent component in some foam concentrates to improve fuel tolerance and fluidity.

FluoroProtein (FP)

A natural protein-based foam concentrate containing flurorocarbon surfactants. Extensively used in oil and petrochemical industries.

Foam Concentrate

A concentrated liquid foaming agent supplied by a manufacturer for mixing with the appropriate amount of water and air to produce finished foam. Also called Foam Compound.

Foam Destroying Action

The ability of polar solvents to collapse standard foam blankets.

Foam Generator

A device designed to introduce air into a pressurised foam solution flow. Also called Foam Maker.

Foaming Agent

A component in foam concentrate responsible for foaming properties. Usually natural protein or synthetic detergent.

Foam Maker

A device designed to introduce air into a pressurized foam solution flow. Also called Foam Generator.

Foam Pourer

A device designed to deliver aspirated foam gently on to a burning liquid.

Foam Quality

A measure of a foam’s physical characteristics expressed in terms of its 25% drainage time and expansion ratio.

Foam Solution

A homogeneous mixture of water and foam concentrate in the correct proportions. Called Premix Solution when in storage.

Foam Spray

Discharge outlet which delivers aerated foam of typical expansion ratio 6-10:1 in a spray pattern.

Forestry Foam

Foam concentrate for use on Class A fuels in vegetation and structural fires.

Freezing Point

The temperature at which foam concentrate solidifies.

Freeze/Thaw Cycle

The process of freezing and thawing out a foam concentrate to assess its storage stability.

Fuel Tolerance

The ability of aspirated foam to withstand contamination by hydrocarbon fuels.

Foam-Water Sprinkler System (FWSS)

A system that is designed to discharge either finished foam through aspirating open sprinkler heads, or non-aspirated foam solution through closed sprinkler heads.

Gelling

AR-AFFF foams that contain polymer can “set” or turn into a gel particularly when stored at low temperatures or when exposed to metal ions.

Glycol Ether

Environmentally hazardous ingredient commonly found in AFFF and AR-AFFF.

Ground Monitor

A monitor designed to be operated at ground-level.

GPM

Gallons per minute.

Gum

Water-soluble ingredient in AR-AFFFs that comes out of solution when brought into contact with polar solvent flammable liquids to form a physical barrier or “raft” that separates the foam blanket from the polar solvent. Also called Polymer. 

Hand Monitor

Monitor designed to be operated by hand.

Hazmat

Abbreviation for Hazardous Material.

Heat Resistance

The ability of a foam blanket to withstand the effects of exposure to heat.

High Expansion

Foam with expansion ratio in the range 201:1 to 2000:1.

High Fluidity

Modern polymerfree Alcohol Resisant foam concentrate.

Hydrocarbon

Fuel based exclusively on chains or rings of linked hydrogen and carbon atoms. Hydrocarbon fuels are not miscible in water.

Hydrocarbon Surfactant

Alternative term for synthetic detergent.

IBC

See Intermediate Bulk Container.

ICAO

See International Civil Aviation Organization

IMO

See International Maritime Organization.

Inductor

A device (portable or fixed) that introduces foam concentrate into the water stream. Also called Eductor or Proportioner.

Intermediate Bulk Container (IBC)

1000 litre capacity container used to supply foam concentrates.

International Civil Aviation Organization (ICAO)

A United Nations (UN) agency which is charged with matters dealing with the development, co-ordination, and preservation of international civil aviation. Publishes “Annex 14 to the Convention on International Civil Aviation, International Standards and  Recommended Practices, Aerodromes, Paragraph 9.2.8” which concludes with a “Note” directing the reader to a test procedure in the ICAO “Airport Service’s Manual, Part 1, Chapter 8 (3rd edition, 1990)”. This test procedure is the most advanced and stringent method for assessing the suitability of foam concentrates for use at modern civilian airports. 

International Maritime Organisation (IMO)

A United Nations (UN) agency which formulates and publishes conventions concerned with maritime safety. Publishes International Convention for Safety of Life at Sea (SOLAS). Publishes standards for foam systems.

Induction Rate

The percentage of foam concentrate mixed or introduced into the water supply line to produce foam solution. Also referred to as Proportioning Rate or Eduction Rate or Pick-Up Rate.

ISO

International Organization for Standardization. Geneva-based worldwide federation of national standards bodies from about 100 countries. Shouldn’t the acronym be “IOS”? Yes, if it were an acronym - which it is not. In fact, “ISO” is a word derived from the Greek “isos” meaning “equal”. From “equal” to “standard”, the line of thinking that led to the choice of “ISO” as the name of the organization is easy to follow. In addition, the name has the advantage of being valid in each of the organization’s three official languages - English, French, and Russian.

Jet-A

Kerosene-grade jet fuel. Also called JP-5.

Jet-B

Jet fuel that is a blend of gasoline and kerosene. Also called JP-4.

Jet Ratio Controller (JRC)

In-line venturi proportioner that proportions foam concentrate as a rich solution (over 60%) to a self inducing large capacity monitor such as Angus Fire Colossus. Allows foam concentrate stocks and operating personnel to be a safe distance from the fire.

JOIFF

Joint Oil and Industry Fire Forum. Leading international organisation for emergency services management in high risk industry.

LASTFIRE

A study of the fire related risks associated with large diameter open-top floating roof storage tanks. Sixteen oil companies are involved in the project which is co-ordinated by Resource Protection International. The LASTFIRE test is designed specifically to determine foam performance related to storage tank fires. Separate nozzle types are used to simulate different application techniques.

LEX

See Low Expansion.

Lloyd’s Register (LR)

World’s leading ship classification society. Approves foam concentrates and foam equipment for marine and offshore applications. Also undertakes independent witness testing.

Low-Expansion (LEX)

Foam with expansion ratio in the range 2:1 to 20:1.

Lowest Use Temperature (LUT)

The lowest temperature at which foam concentrate can be used through conventional equipment such as venturi proportioning devices.

LUT

See Lowest Use Temperature.

Material Safety Data Sheet (MSDS)

Document that communicates hazards associated with a product to  the user. With the introduction of the UK Chemicals (Hazard Information and Packaging) Regulations 1993 and subsequent Regulations (CHIP 2 and amending CHIP 96 Regulations), it has become a mandatory  requirement for the supplier of potentially hazardous products to send an MSDS to the customer. What is  more, this MSDS must contain certain information presented in a standard format with 16 headings.

Marine Safety Agency (MSA)

UK agency that publishes regulations concerning safety on ships and the prevention of marine pollution. Approves foam concentrates and foam equipment.

Medium-Expansion (MEX)

Foam with expansion ratio in the range 21:1 to 200:1.

Methyl Tertiary Butyl Ether (MTBE)

Mildly polar flammable liquid used as a component in unleaded  gasoline. Alcoseal and FP70 Plus are UL Listed for use on MTBE.

MEX

See Medium Expansion.

MIL-F

US military specification MILF- 24385F. Limited to testing AFFF and so cannot be used for more advanced FFFP foams. Today largely superceded at civilian airports by new ICAO foam standard. See Qualified Products List.

Ministry of Defence (MOD)

UK Minstry of Defence publishes Defence Standards 42-40 (hydrocarbon type foams) and 42-41 (alcohol resistant foams).

Monitor

A portable, fixed or truck-mounted device to which a large-throughput foam nozzle or cannon is attached to allow the operator to direct the water or foam as required. eg. Angus Fire Streamline range.

MSDS

See Material Safety Data Sheet.

MTBE

See Methyl Tertiary Butyl Ether.

National Fire Protection Association (NFPA)

US organisation that is committed to protecting people, property, and the environment from the effects of fire. It has a membership of over 60,000 from over 85 countries. It develops, publishes, and disseminates many standards relating to foam (eg. NFPA 11 Standard for Low-Expansion Foam).

NATO (North Atlantic Treaty Organisation)

Paris-based alliance of over 15 countries near or on the North Atlantic Ocean and the Mediterranean Sea. Provides joint action in time of war, and joint military and economic cooperation in time of peace. Issues stock numbers for foam concentrates and foam equipment.

Newtonian

Foam concentrate that displays constant viscosity at various shear rates.

NFPA

See National Fire Protection Association.

Non-Aspirated

Foam with expansion ratio in the range 1-2:1. The only aeration is the result of air entrainment and impact. Only filmforming foam concentrates are suitable for non-aspirating applications. Also referred to as Unaspirated.

Non-Newtonian

Foam concentrate that displays different viscosity at different shear rates.

OECD (Organisation of Economic Cooperation and Development)

Paris-based economic think-tank for the world’s richest nations. Publishes guidelines for the environmental testing of chemicals such as foam concentrates.

pH

Measurement of acidity to alkalinity on a scale of 1 to 14. Neutral is 7. Acidic is less than 7. Alkaline is greater than 7.

Phase Separation

What happens when AR-AFFF separates into two phases - a thin phase (water and solvent) and a thick phase (hydrated polymer).

Pick-Up Rate

The percentage of foam concentrate mixed or introduced into the water supply line to  produce foam solution. Also referred to as Induction Rate or Eduction Rate or Proportioning Rate.

Polar Solvent

A liquid whose molecules possess a permanent electric moment (eg. alcohols, amines, ethers, esters, aldehydes, ketones). In fire fighting any flammable liquid that destroys standard foam is generally referred to as a polar solvent. Polar solvents are generally miscible with water.

Polymer

Water-soluble ingredient in AR-AFFFs that comes out of solution when brought into contact with polar solvent flammable liquids to form a physical barrier or “raft” that separates the foam blanket from the polar solvent. Also called Gum.

Polymer-Free

Modern AR-FFFP, such as Niagara, no longer use polymer to achieve alcohol resistance.

Portable Foam Equipment

Foam production equipment that is easily transportable by hand.

Portable Foam Inductor

Inductor that is easily transportable by hand.

Post-Fire Security

Ability of foam to prevent heat sources from reigniting fuel after extinguishment.

Pour Point

The lowest temperature at which foam concentrate is fluid enough to pour. Generally a few degrees above its freezing point.

Pre-burn Time

The time between ignition of a fire and the commencement of foam application.

Premix

A mixture of foam concentrate and water in the correct proportions which can be stored for a  specified time.

Protein (P)

Foam concentrate based on natural protein foaming agent. Also known as Standard Protein or Regular Protein.

Proportioner

A device that introduces foam concentrate. Also referred to as Inductor or Eductor.

Proportioning Rate

The percentage of foam concentrate mixed or introduced into the water supply line to produce foam solution. Also referred to as Induction Rate, Eduction Rate or Pick-Up Rate.

UL 162 (7th Edition) and NFPA 11 (1994) both state that foam proportioning must be not less than the recommended concentration, and no more than 30% above the recommended concentration, or 1% above the recommended concentration, whichever is less. What this means is that 1% concentrates must be proportioned in the range 1.0 - 1.3%; 3% concentrates must be proportioned in the range 3-0 - 3.9%; and 6% concentrates must be proportioned in the range 6.0 - 7.0%.

Pseudoplastic

A non-Newtonian foam concentrate that displays a decreasing viscosity with an increasing shear rate. Also called Shear-Thinning.

Pump

Foam concentrate pumps are usually either positive displacement pumps (recommended by NFPA for foam concentrates) or centrifugal foam pumps (limited to low viscosity foam concentrates).

Qualified Products List (QPL)

AFFF products that have been qualified under US military specification MIL-F-24385F.

RIV

Rapid Intervention Vehicle

Refractometer

A device used to measure the amount of foam concentrate in solution. This device operates on the principle of measuring the velocity of light that travels throught the foam solution.

Remote Control Monitor

Commonly used to protect jetties, offshore platforms, oil tankers, chemical carriers, and on fire fighting tugs.

Refractive Index (RI)

As measured using a Refractometer. Determines the amount of foam concentrate in solution on the principle of measuring the velocity of light that travels throught the foam solution.

Rimseal Foam Generator (RFG)

Device permanently installed on floating roof storage tank that is designed to produce aspirated foam from foam solution.

Rimseal Foam Pourer (RFP)

Device permanently installed on floating roof storage tank that is designed to discharge aspirated foam gently on to the rimseal area.

SCBA

Self-Contained Breathing Apparatus.

SHE

Safety, Health and Evironment.

Sediment

The proportion in percentage by volume of solid matter which can be centrifuged out of a foam concentrate. Also called Sludge or Undissolved Solids.

Semi-Fixed

Foam equipment that is easily transportable and operates without supervision.

Semi-Subsurface Injection

A system used to the protection of fixed roof hydrocarbon and water soluble fuel storage tanks where foam is directed to the fuel surface from the bottom of the tank through a flexible hose normally contained in a sealed container.

SG

See Specific Gravity.

Shear-Thinning

A non-Newtonian foam concentrate that displays a decreasing viscosity with an increasing shear rate. Also called Pseudoplastic.

Shear Rate

The rate at which foam is subjected to shearing.

Specific Gravity (SG)

Density of foam concentrate divided by density of water. Liquids with an SG less than one are lighter than water and will therefore float on water. Those with an SG greater than one are heavier than water and will sink to the bottom.

Spreading Coefficient (SC)

A foam solution that has a spreading coefficient greater than zero is  film-forming. Defined as the surface tension of cylohexane minus the surface tension of foam solution minus the interfacial tension of cyclohexane and foam solution.

Sprinkler - Foam-Water Type

An air aspirating open type sprinkler constructed to discharge water or foam-water solutions.

Sprinkler - Standard

A non-air aspirating type sprinkler that discharges water or film-forming foam solutions.

Stability

A term used with foam concentrates to determine the performance and security of a foam blanket.

Storage Stability

The ability of foam concentrate to withstand long-term storage under varying environmental conditions.

Surface Tension

The tension in the interface between foam solution and air. Unit is dyne/cm which is equivalent to mN/m. Typical values are water 72 dyne/cm, Protein 40 dyne/cm, FluoroProtein 20-30 dyne/cm, FFFP/AFFF <20 dyne/cm.

Surfactant

Abbreviation for Surface Active Agent. Chemical that reduces the surface tension of water. Examples used in foam concentrates include Hydocarbon Surfactants (also called Detergent) and Fluorocarbon Surfactant.

Synthetic

Foam whose main ingredient is synthetic detergent. eg. AFFF, AR-AFFF (as opposed to Protein Foams).

Training Foam

Foam concentrate that is formulated especially for training exercises.

Transit Time

The time taken for foam solution to pass from the point where foam concentrate is induced into the water supply to where aeration takes place.

Ullage

A space that should be allowed above a foam concentrate in a bulk storage tank to accommodate  the differences in thermal expansion coefficient between the tank construction material and the foam  concentrate. Generally a meaure of 5 to 10% of the tank volume is more than adequate.

Unaspirated

Foam with expansion ratio in the range 1: 1 to 2:1.

Underwriters Laboratories (UL)

US organisation with a high reputation for independent assurance of foam concentrate and foam equipment product quality. The names of companies that have demonstrated an ability to manufacture produts that meet UL requirements are published annually in the UL Fire Protection Equipment Directory. The standard used to evaluate products is UL 162 Standard for Foam Equipment and Liquid Concentrates (7th edition). Further information on UL 162 can be found here.

Undissolved Solids

See Sludge.

Rf

Fully fluorinated (in regards to carbon chain lengths)

Variable Inductor

A portable foam inductor capable of inducing foam at various percentages, usually in the range 1% to 6%.

Vapour Suppression

The use of foam to suppress hazardous vapours or prevent ignition in the event of an accidental spillage of a hazardous liquid. Products include VapourShield (Alkali) and VapourShield (Acid) C6.

Venturi

A constricted portion of a pipe or tube which will increase water velocity, thus momentarily reducing its pressure, and simultaneously creating a vacuum.

Viscosity

The thickness of a liquid or its ability to flow. Normally measured in Ostwald U-tube viscometers giving kinematic viscosities in Centistokes (cs) which are equivalent to mm²/sec (SI units). Viscosities can also be quoted in a wide range of other units, most commonly as dynamic viscosity in Centipoise or Poise. Kinematic Viscosity is the same as Dynamic Viscosity divided by Density. eg. Water at 20⁰C with density 1g/cm³, kinematic viscosity = 1 cs, and dynamic viscosity = 1 centipoise.