Firefighter Certification key terms

A rule requiring at least two firefighters to enter an IDLH atmosphere as a team while two more remain outside, ready to rescue them. It applies to structural firefighting and is tied to accountability.

The radio term a firefighter uses to announce that they are lost, trapped, out of air, or otherwise in immediate danger and need rescue. It signals a switch to emergency traffic.

A planned rest and recovery period at an incident where crews are checked, cooled or warmed, rehydrated, and monitored before returning to work. It reduces heat stress and fatigue-related injuries.

A model of combustion showing four required elements: fuel, oxygen, heat, and an uninhibited chemical chain reaction. Removing any one element stops the burning.

The near-simultaneous ignition of all exposed combustible surfaces in a compartment, caused by heat buildup and radiant feedback. It marks the transition from a growing fire to a fully developed fire.

A violent explosion that occurs when oxygen suddenly enters a hot, fuel-rich, ventilation-limited space and ignites, often when a door or window is opened. It is signaled by pressurized smoke and inward air movement.

The chemical breakdown of a solid material by heat into combustible gases, occurring before those gases actually ignite. It explains why solid fuels burn with flames in the gas phase.

Building methods using engineered components such as trusses and thin gusset plates instead of heavy solid members. These assemblies fail quickly under fire, so crews must limit interior time and watch for collapse indicators.

An arched roof truss with a curved top chord and a straight bottom chord, often found in older commercial buildings. Its hidden connections are prone to early failure and it can collapse without warning.

A piped network of heat-activated heads that discharge water onto a fire automatically. It controls or extinguishes a fire in its early stage and is among the most effective built-in fire protection features.

A fixed piping system with hose outlets at various levels of a building that lets firefighters connect hose and get water high up without stretching lines from the street.

A backpack-mounted unit supplying filtered compressed air through a facepiece so the wearer can breathe safely in smoke, toxic gas, or oxygen-deficient atmospheres. It includes a cylinder, regulator, and low-air alarm.

A personal alert safety system worn by firefighters that sounds a loud alarm if the wearer stops moving for a set time or manually activates it, helping rescuers locate a downed member.

The ensemble of coat, pants, helmet, hood, gloves, and boots designed to shield firefighters from heat, flame, and water. It does not protect against all chemical or electrical hazards.

The process of blocking and bracing a vehicle or object so it cannot move during rescue operations. It is completed before rescuers enter or lift, preventing sudden shifts that injure patients and crews.

Stacked wooden or plastic blocks placed under a lifted object to hold it in position. Rescue teams build box cribs so the load stays supported even if hydraulic tools lose pressure.

The paired hand tools of a flat-head axe and a pry bar, commonly a halligan. Together they allow firefighters to pry, strike, gap, and force most common doors and windows.

Cutting an opening in the roof or highest point of a structure to release hot smoke and gases upward. It improves interior visibility and reduces flashover potential when coordinated with fire attack.

Using a fog stream directed out a window or door to create air movement that pulls smoke from a room. The nozzle is placed near the opening so the cone covers most of it.

A ground ladder with two or more sections that slide or rope-operate to reach greater heights. Firefighters raise it to windows and roofs for access, rescue, and ventilation.

The angle at which a ground ladder leans against a building, recommended near 75 degrees, roughly one-quarter of the ladder length out from the wall. Too steep or too shallow reduces stability.

A rapid, systematic search of the fire area for victims, done early and often before hose lines are fully in place. Speed and thoroughness in the most threatened spaces matter most.

A slower, more thorough search conducted after the fire is knocked down, covering all spaces including hidden ones to confirm no victims remain. It is not a substitute for the primary search.

The pressure lost as water moves through hose, pipes, and fittings because of turbulence and contact with the walls. It increases with flow rate, hose length, and smaller diameter.

A pressure surge caused by suddenly stopping or changing water flow in a pipe or hose, which can damage hose, pumps, and plumbing. Operators close valves slowly to prevent it.

The pressure measured at the nozzle needed to produce the desired stream, such as 50 psi for a handline smooth bore. It is a key input when calculating pump discharge pressure.

The volume of water per minute needed to control a fire in a given building or space. It is estimated from the size and construction of the involved area and drives water supply decisions.

The stage after fire control where crews open concealed spaces and wet down smoldering material to prevent rekindling. It is also when evidence of fire cause is protected and discovered.

A heavy, water-resistant canvas or synthetic sheet used to protect furniture, stock, and undamaged areas from water and smoke damage. Properly placed covers reduce loss beyond the fire itself.

The specific location where a fire started, determined from burn patterns, witness statements, and analysis. Identifying it is the first step before determining the cause.

A reference book used at hazardous materials incidents to find initial isolation distances, protective actions, and hazard information by a material's four-digit identification number or placard.

Immediately dangerous to life or health: an atmosphere that can cause death, irreversible harm, or impair a person's ability to escape. Firefighters need full respiratory protection and often chemical protective clothing in these conditions.

The contaminated area at a hazardous materials incident where only trained personnel in appropriate protective equipment may work. Entry is controlled through a decontamination corridor at its boundary.

A planned route where people and equipment leaving the hot zone are cleaned to remove hazardous material. It sits between the contaminated and clean areas and prevents spreading the substance.

A written or verbal plan for an operational period that states objectives, strategies, tactics, and assignments. It gives responders a common picture and is updated as conditions change.

The number of people or resources one supervisor can effectively direct, commonly three to seven with five as a target. Exceeding it calls for splitting the unit into smaller groups.

The principle that each responder reports to only one supervisor at an incident. It prevents conflicting orders and confusion during fast-moving operations.

A roll-call confirmation that all assigned members are accounted for, typically requested at benchmarks or after a Mayday. Crews report by team so missing members are identified quickly.