Hazmat Technician key terms

A four-digit number assigned to a specific hazardous material and shown on placards, shipping papers, and packages to help responders quickly identify the substance involved in an incident.

A diamond-shaped warning sign affixed to vehicles and containers that communicates the general hazard class and, when present, the UN number of the material inside.

A fixed-facility marking system using a four-quadrant diamond to rate health, flammability, instability, and special hazards on a 0-to-4 severity scale for emergency responders.

A reference published for first responders that assigns guide numbers to hazardous materials by UN number or name, listing initial isolation distances and protective actions.

A standardized document provided by manufacturers that describes a chemical's hazards, physical properties, health effects, and required handling and first-aid measures.

The practice of reading non-verbal indicators at an incident, such as odors, dead vegetation, container shapes, and vapor patterns, to form preliminary hazard hypotheses before identification.

The pressure exerted by a vapor in equilibrium with its liquid at a given temperature; higher values indicate a material that evaporates readily and can produce dangerous airborne concentrations.

The weight of a gas or vapor compared with an equal volume of air; values above one mean the substance tends to settle in low areas and confined spaces.

The ratio of a liquid's density to that of water; liquids with values below one float on water and may spread fire or contaminate waterways.

The lowest temperature at which a liquid gives off enough vapor to ignite briefly when exposed to an ignition source, indicating relative fire hazard.

The range of vapor concentrations in air between the lower and upper explosive limits within which ignition and combustion can occur.

The temperature at which a material ignites spontaneously without an external ignition source, an important consideration when heating or transferring products.

The tendency of a substance to react violently with water, releasing heat, flammable gas, or toxic vapor, which dictates that water must not be used as an extinguishing agent.

Immediately Dangerous to Life or Health: the maximum airborne concentration from which a worker could escape within thirty minutes without irreversible health effects or escape-impairing symptoms.

A regulatory occupational exposure limit, typically expressed as a time-weighted average over an eight-hour shift, that defines acceptable workplace airborne concentrations of a substance.

The ability of a material to destroy living tissue or severely corrode metal, generally defined by pH extremes or measured metal loss rates.

A zero-to-fourteen scale expressing the acidity or alkalinity of an aqueous solution, with values below seven acidic and above seven basic.

The OSHA regulation requiring employers to inform workers about chemical hazards through labels, safety data sheets, and training.

The OSHA standard governing hazardous waste operations and emergency response, setting training, medical surveillance, and site safety requirements for responders.

A written or verbal plan that states incident objectives, strategies, tactics, and assigned resources for a defined operational period.

A document identifying site hazards, control measures, personal protective equipment requirements, decontamination procedures, and medical support for operations at a hazardous materials scene.

The highest level of chemical protective clothing, consisting of a fully encapsulating vapor-tight suit with self-contained breathing apparatus worn inside, used for unknown or highly hazardous atmospheres.

Chemical protective clothing offering splash protection with self-contained breathing apparatus worn outside the suit, used when the atmosphere requires respiratory protection but not full vapor encapsulation.

A respiratory protection device that supplies breathable air from an onboard cylinder, allowing work in atmospheres immediately dangerous to life or health.

An organized sequence of stations where responders and equipment are washed, rinsed, and checked to remove contaminants before leaving the hot zone.

The initial, rapid removal of the bulk of contaminants from people or equipment, often by stripping outer clothing and washing with water and detergent, before more thorough decontamination.

A more thorough, systematic cleaning process using specific solutions, tools, and verification steps to reduce contamination to acceptable levels on responders and equipment.

A monitoring instrument that measures the concentration of flammable gas or vapor in air and displays it as a percentage of the lower explosive limit.

A monitoring device that uses ultraviolet light to ionize airborne chemicals and estimate total volatile organic vapor concentrations, useful for screening unknown atmospheres.

A colorimetric sampling device in which air is drawn through a reagent-filled tube and a color change indicates the concentration of a specific chemical.

The minimum concentration of flammable vapor in air below which the mixture is too lean to ignite, expressed as a percentage of volume.

Building a barrier of soil, sand, or absorbent material around a spilled liquid to prevent it from spreading or entering drains and waterways.

Constructing a barrier across a flowing channel to stop or divert the movement of a liquid product, often used in waterways to protect downstream areas.

A containment technique in which a material such as clay, sand, or synthetic pads takes up a liquid spill so it can be collected and removed.

The contaminated area immediately surrounding a hazardous materials release where only trained personnel in appropriate protective equipment may operate.

The controlled transition area between the hot and cold zones where decontamination, equipment staging, and support functions occur.

The uncontaminated area outside the control line where the command post, medical support, and other support operations are located.

A standardized, modular management structure that organizes personnel, resources, and communications around common objectives during emergency incidents.

An incident management arrangement in which agencies with jurisdiction or responsibility jointly set objectives and coordinate operations under a single command structure.

Chemical, biological, radiological, nuclear, or explosive devices or agents intended to cause mass casualties, disruption, or fear among a population.

An illegal operation for manufacturing drugs or chemical agents, often improvised and containing unstable mixtures, toxic vapors, and improvised equipment that pose severe hazards to responders.

An additional explosive or weapon placed to injure responders and civilians who gather after an initial attack, a common tactic in terrorist incidents.

A bomb constructed from non-standard components and often concealed or delivered unconventionally, requiring bomb technicians rather than hazmat personnel to handle.

Immediate, improvised washing of victims using available water and equipment to remove contaminants and reduce exposure before formal decontamination.

The process of sorting patients by injury severity and treatment urgency so that limited resources are directed to those most likely to benefit.

The tactics used to confine, contain, and recover released hazardous materials, including diking, damming, absorption, and vapor suppression.

The final phase of an incident in which operations are concluded, equipment and personnel are accounted for, decontamination is verified, and documentation and critique are completed.

The visible or invisible cloud of vapor, smoke, or aerosol that travels downwind from a release, used to predict affected areas and protective action distances.

The tendency of a substance to undergo chemical change, especially violently, when mixed with other materials, heated, or exposed to air, water, or light.

A written or verbal plan that states incident objectives, strategies, tactics, and assigned resources for a defined operational period.