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Glossary

Adsorption
In this guidebook, means a process by which a gas adheres to the surface of a solid but does not penetrate it, such as in adsorption of gases by activated carbon (charcoal).
AEGL(s)
Acute Exposure Guideline Level(s), AEGLs represent threshold exposure limits for the general public after a once-in-a-lifetime, or rare, exposure and are applicable to emergency exposure periods ranging from 10 minutes to 8 hours. Three levels AEGL-1, AEGL-2 and AEGL-3 are developed for each of five exposure periods (10 and 30 minutes, 1 hour, 4 hours, and 8 hours) and are distinguished by varying degrees of severity of toxic effects; see AEGL-1, AEGL-2 and AEGL-3.
AEGL-1
AEGL 1 is the airborne concentration (expressed as parts per million or milligrams per cubic meter [ppm or mg/m3]) of a substance above which it is predicted that the general population, including susceptible individuals, could experience notable discomfort, irritation, or certain asymptomatic, non sensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.
AEGL-2
AEGL 2 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience irreversible or other serious, long lasting adverse health effects or an impaired ability to escape.
AEGL-3
AEGL 3 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience life threatening health effects or death.
Alcohol-resistant foam
A foam that is resistant to "polar" chemicals such as ketones and esters which may break down other types of foam.
Biological agents
Living organisms that cause disease, sickness and mortality in humans. Anthrax and Ebola are examples of biological agents. Refer to Guide 158.
Blister agents (vesicants)
Substances that cause blistering of the skin. Exposure is through liquid or vapor contact with any exposed tissue (eyes, skin, lungs). Mustard (H), Distilled Mustard (HD), Nitrogen Mustard (HN) and Lewisite (L) are blister agents.
Symptoms: Red eyes, skin irritation, burning of skin, blisters, upper respiratory damage, cough, hoarseness.
Blood agents
Substances that injure a person by interfering with cell respiration (the exchange of oxygen and carbon dioxide between blood and tissues). Hydrogen cyanide (AC) and Cyanogen chloride (CK) are blood agents.
Symptoms: Respiratory distress, headache, unresponsiveness, seizures, coma.
Burn
Refers to either a chemical or thermal burn, the former may be caused by corrosive substances and the latter by liquefied cryogenic gases, hot molten substances, or flames.
Carcinogen
A substance or mixture which induces cancer or increases its incidence.
Category A
An infectious substance that poses a high risk to the health of individuals and/or animals or public health. These substances can cause serious disease and can lead to death. Effective treatment and preventative measures may not be available.
Category B
An infectious substance that poses a low to moderate risk to individuals and/or animals and/or public health. These substances are unlikely to cause serious disease. Effective treatment and preventative measures are available.
CBRN
Chemical, biological, radiological or nuclear warfare agent.
Choking agents
Substances that cause physical injury to the lungs. Exposure is through inhalation. In extreme cases, membranes swell and lungs become filled with liquid (pulmonary edema). Death results from lack of oxygen; hence, the victim is "choked". Phosgene (CG) is a choking agent.
Symptoms: Irritation to eyes/nose/throat, respiratory distress, nausea and vomiting, burning of exposed skin.
CO2
Carbon dioxide gas.
Cold zone
Area where the command post and support functions that are necessary to control the incident are located. This is also referred to as the clean zone, green zone or support zone in other documents. (EPA Standard Operating Safety Guidelines, OSHA 29 CFR 1910.120, NFPA 472).
Combustible liquid
Liquids which have a flash point greater than 60°C (140°F) and below 93°C (200°F). U.S. regulations permit a flammable liquid with a flash point between 38°C (100°F) and 60°C (140°F) to be reclassed as a combustible liquid.
Compatibility Group
Letters identify explosives that are deemed to be compatible. The definition of these Compatibility Groups in this Glossary are intended to be descriptive. Please consult the transportation of dangerous goods/hazardous materials or explosives regulations of your jurisdiction for the exact wording of the definitions. Class 1 materials are considered to be "compatible" if they can be transported together without significantly increasing either the probability of an incident or, for a given quantity, the magnitude of the effects of such an incident.

A
Substances which are expected to mass detonate very soon after fire reaches them.
B
Articles which are expected to mass detonate very soon after fire reaches them.
C
Substances or articles which may be readily ignited and burn violently without necessarily exploding.
D
Substances or articles which may mass detonate (with blast and/or fragment hazard) when exposed to fire.
E & F
Articles which may mass detonate in a fire.
G
Substances and articles which may mass explode and give off smoke or toxic gases.
H
Articles which in a fire may eject hazardous projectiles and dense white smoke.
J
Articles which may mass explode.
K
Articles which in a fire may eject hazardous projectiles and toxic gases.
L
Substances and articles which present a special risk and could be activated by exposure to air or water.
N
Articles which contain only extremely insensitive detonating substances and demonstrate a negligible probability of accidental ignition or propagation.
S
Packaged substances or articles which, if accidentally initiated, produce effects that are usually confined to the immediate vicinity.
Control zones
Designated areas at dangerous goods incidents, based on safety and the degree of hazard. Many terms are used to describe control zones; however, in this guidebook, these zones are defined as the hot/exclusion/red/restricted zone, warm/contamination reduction/yellow/limited access zone, and cold/support/green/clean zone. (EPA Standard Operating Safety Guidelines, OSHA 29 CFR 1910.120, NFPA 472).
Cryogenic liquid
A refrigerated, liquefied gas that has a boiling point colder than -90°C (-130°F) at atmospheric pressure.
Decomposition products
Products of a chemical or thermal break-down of a substance.
Decontamination
The removal of dangerous goods from personnel and equipment to the extent necessary to prevent potential adverse health effects. Always avoid direct or indirect contact with dangerous goods; however, if contact occurs, personnel should be decontaminated as soon as possible. Since the methods used to decontaminate personnel and equipment differ from one chemical to another, contact the chemical manufacturer, through the agencies listed on the inside back cover, to determine the appropriate procedure. Contaminated clothing and equipment should be removed after use and stored in a controlled area (warm/contamination reduction/yellow/limited access zone) until cleanup procedures can be initiated. In some cases, protective clothing and equipment cannot be decontaminated and must be disposed of in a proper manner.
Dry chemical
A preparation designed for fighting fires involving flammable liquids, pyrophoric substances and electrical equipment. Common types contain sodium bicarbonate or potassium bicarbonate.
Edema
The accumulation of an excessive amount of watery fluid in cells and tissues. Pulmonary edema is an excessive buildup of water in the lungs, for instance, after inhalation of a gas that is corrosive to lung tissue.
ERPG(s)
Emergency Response Planning Guideline(s). Values intended to provide estimates of concentration ranges above which one could reasonably anticipate observing adverse health effects; see ERPG-1, ERPG-2 and ERPG-3.
ERPG-1
The maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 hour without experiencing more than mild, transient adverse health effects or without perceiving a clearly defined objectionable odor.
ERPG-2
The maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptoms that could impair an individual's ability to take protective action.
ERPG-3
The maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 hour without experiencing or developing life-threatening health effects.
Flammable liquid
A liquid that has a flash point of 60°C (140°F) or lower.
Flash point
Lowest temperature at which a liquid or solid gives off vapor in such a concentration that, when the vapor combines with air near the surface of the liquid or solid, a flammable mixture is formed. Hence, the lower the flash point, the more flammable the material.
Hazard zones (Inhalation Hazard Zones)
HAZARD ZONE A:
Gases: LC50 of less than or equal to 200 ppm,

Liquids: V equal to or greater than 500 LC50 and LC50 less than or equal to 200 ppm,
HAZARD ZONE B:
Gases: LC50 greater than 200 ppm and less than or equal to 1000 ppm,

Liquids: V equal to or greater than 10 LC50; LC50 less than or equal to 1000 ppm and criteria for Hazard Zone A are not met.
HAZARD ZONE C:
LC50 greater than 1000 ppm and less than or equal to 3000 ppm,
HAZARD ZONE D:
LC50 greater than 3000 ppm and less than or equal to 5000 ppm.
Hot zone
Area immediately surrounding a dangerous goods incident which extends far enough to prevent adverse effects from released dangerous goods to personnel outside the zone. This zone is also referred to as exclusion zone, red zone or restricted zone in other documents. (EPA Standard Operating Safety Guidelines, OSHA 29 CFR 1910.120, NFPA 472).
IED
Immiscible
In this guidebook, means that a material does not mix readily with water.
Improvised Explosive Device
A bomb that is manufactured from commercial, military or homemade explosives.
Large spill
A spill that involves quantities that are greater than 208 liters (55 US gallons) for liquids and greater than 300 kilograms (660 pounds) for solids.
LC50
Lethal concentration 50. The concentration of a material administered by inhalation that is expected to cause the death of 50% of an experimental animal population within a specified time. (Concentration is reported in either ppm or mg/m3).
Mass explosion
Explosion which affects almost the entire load virtually instantaneously.
MAWP
Maximum Allowable Working Pressure: The maximum allowable internal pressure that the tank may experience during normal operations.
mg/m3
Milligrams of a material per cubic meter of air.
Miscible
In this guidebook, means that a material mixes readily with water.
mL/m3
Milliliters of a material per cubic meter of air. (1 mL/m3 equals 1 ppm).
Mutagen
An agent giving rise to an increased occurrence of mutations in populations of cells and/or organisms. Mutation means a permanent change in the amount or structure of the genetic material in a cell.
Narcotic
A substance which acts as a central nervous system depressor producing effects such as drowsiness, narcosis, reduced alertness, loss of reflexes, lack of coordination, and vertigo. These effects can also be manifested as severe headache or nausea, and can lead to reduced judgment, dizziness, irritability, fatigue, impaired memory function, deficit in perception and coordination, reaction time, or sleepiness.
Nerve agents
Substances that interfere with the central nervous system. Exposure is primarily through contact with the liquid (via skin and eyes) and secondarily through inhalation of the vapor. Tabun (GA), Sarin (GB), Soman (GD) and VX are nerve agents.
Symptoms: Pinpoint pupils, extreme headache, severe tightness in the chest, dyspnea, runny nose, coughing, salivation, unresponsiveness, seizures.
n.o.s.
These letters refer to "not otherwise specified". The entries which use this description are generic names such as "Corrosive liquid, n.o.s." This means that the actual chemical name for that corrosive liquid is not listed in the regulations; therefore, a generic name must be used to describe it on shipping papers.
Noxious
In this guidebook, means that a material may be harmful or injurious to health or physical well-being.
Oxidizer
A chemical which supplies its own oxygen and which helps other combustible material burn more readily.
P
Packing Group
The Packing Group (PG) is assigned based on the degree of danger presented by the hazardous material:

PG I :
Great danger
PG II :
Medium danger
PG III :
Minor danger
PG
pH
pH is a value that represents the acidity or alkalinity of a water solution. Pure water has a pH of 7. A pH value below 7 indicates an acid solution (a pH of 1 is extremely acidic). A pH above 7 indicates an alkaline solution (a pH of 14 is extremely alkaline). Acids and alkalies (bases) are commonly referred to as corrosive materials.
PIH
Poison Inhalation Hazard. Term used to describe gases and volatile liquids that are toxic when inhaled. (Same as TIH).
Polar
Polymerization
A chemical reaction that often produces heat and pressure. Once initiated, the reaction is accelerated by the heat that it produces. The uncontrolled buildup of heat and pressure can cause a fire or an explosion, or can rupture closed containers. The letter (P) following a guide number in the yellow-bordered and blue-bordered pages identifies a material that may polymerize violently under high temperature conditions or contamination with other products. It is also used to identify materials that have a strong potential for polymerization in the absence of an inhibitor due to depletion of this inhibitor caused by accident conditions.
ppm
Parts per million. (1 ppm equals 1 mL/m3)
Includes both respiratory and physical protection. One cannot assign a level of protection to clothing or respiratory devices separately. These levels were accepted and defined by response organizations such as U.S. Coast Guard, NIOSH, and U.S. EPA.

Level A:
SCBA plus totally encapsulating chemical resistant clothing (permeation resistant).
Level B:
SCBA plus hooded chemical resistant clothing (splash suit).
Level C:
Full or half-face respirator plus hooded chemical resistant clothing (splash suit).
Level D:
Coverall with no respiratory protection.
Pyrophoric
A material which ignites spontaneously upon exposure to air (or oxygen).
Radiation Authority
As referred to in GUIDES 161 through 166 for radioactive materials, the Radiation Authority is either a Federal, state/provincial agency or state/province designated official. The responsibilities of this authority include evaluating radiological hazard conditions during normal operations and during emergencies. If the identity and telephone number of the authority are not known by emergency responders, or included in the local response plan, the information can be obtained from the agencies listed on the inside back cover. They maintain a periodically updated list of radiation authorities.
Radioactivity
The property of some substances to emit invisible and potentially harmful radiation.
Refrigerated liquid
Respiratory sensitizer
A substance that induces hypersensitivity of the airways following inhalation of the substance.
Right-of-way
A defined area on a property containing one or more high-pressure natural gas pipelines.
Shelter in-place
People should seek shelter inside a building and remain inside until the danger passes. Sheltering in-place is used when evacuating the public would cause greater risk than staying where they are, or when an evacuation cannot be performed. Direct the people inside to close all doors and windows and to shut off all ventilating, heating and cooling systems. In-place protection (shelter in-place) may not be the best option if (a) the vapors are flammable; (b) if it will take a long time for the gas to clear the area; or (c) if buildings cannot be closed tightly. Vehicles can offer some protection for a short period if the windows are closed and the ventilating systems are shut off. Vehicles are not as effective as buildings for in-place protection.
Skin corrosion
The production of irreversible damage to the skin following the application of a test substance for up to 4 hours.
Skin irritation
The production of reversible damage to the skin following the application of a test substance for up to 4 hours.
Skin sensitizer
A substance that will induce an allergic response following skin contact.
Small spill
A spill that involves quantities that are less than 208 liters (55 US gallons) for liquids and less than 300 kilograms (660 pounds) for solids.
Specific gravity
Weight of a substance compared to the weight of an equal volume of water at a given temperature. Specific gravity less than 1 indicates a substance is lighter than water; specific gravity greater than 1 indicates a substance is heavier than water.
Straight (solid) stream
Method used to apply or distribute water from the end of a hose. The water is delivered under pressure for penetration. In an efficient straight (solid) stream, approximately 90% of the water passes through an imaginary circle 38 cm (15 inches) in diameter at the breaking point. Hose (solid or straight) streams are frequently used to cool tanks and other equipment exposed to flammable liquid fires, or for washing burning spills away from danger points. However, straight streams will cause a spill fire to spread if improperly used or when directed into open containers of flammable and combustible liquids.
Toxic Inhalation Hazard. Term used to describe gases and volatile liquids that are toxic when inhaled. (Same as PIH).
V
Saturated vapor concentration in air of a material in mL/m3 (volatility) at 20°C and standard atmospheric pressure.
Vapor density
Weight of a volume of pure vapor or gas (with no air present) compared to the weight of an equal volume of dry air at the same temperature and pressure. A vapor density less than 1 (one) indicates that the vapor is lighter than air and will tend to rise. A vapor density greater than 1 (one) indicates that the vapor is heavier than air and may travel along the ground.
Vapor pressure
Pressure at which a liquid and its vapor are in equilibrium at a given temperature. Liquids with high vapor pressures evaporate rapidly.
Viscosity
Measure of a liquid's internal resistance to flow. This property is important because it indicates how fast a material will leak out through holes in containers or tanks.
Warm zone
Area between Hot and Cold zones where personnel and equipment decontamination and hot zone support take place. It includes control points for the access corridor and thus assists in reducing the spread of contamination. Also referred to as the contamination reduction corridor (CRC), contamination reduction zone (CRZ), yellow zone or limited access zone in other documents. (EPA Standard Operating Safety Guidelines, OSHA 29 CFR 1910.120, NFPA 472).
For the purposes of this guidebook, produces significant toxic gas when it comes in contact with water.
Water-sensitive
Substances which may produce flammable and/or toxic decomposition products upon contact with water.
Water spray (fog)

Method or way to apply or distribute water. The water is finely divided to provide for high heat absorption. Water spray patterns can range from about 10 to 90 degrees. Water spray streams can be used to extinguish or control the burning of a fire or to provide exposure protection for personnel, equipment, buildings, etc. (This method can be used to absorb vapors, knock-down vapors or disperse vapors. Direct a water spray (fog), rather than a straight (solid) stream, into the vapor cloud to accomplish any of the above).

Water spray is particularly effective on fires of flammable liquids and volatile solids having flash points above 37.8°C (100°F).

Regardless of the above, water spray can be used successfully on flammable liquids with low flash points. The effectiveness depends particularly on the method of application. With proper nozzles, even gasoline spill fires of some types have been extinguished when coordinated hose lines were used to sweep the flames off the surface of the liquid. Furthermore, water spray carefully applied has frequently been used with success in extinguishing fires involving flammable liquids with high flash points (or any viscous liquids) by causing frothing to occur only on the surface, and this foaming action blankets and extinguishes the fire.

Date Modified:
2016-08-25