It also does not prohibit firefighters from entering a burning structure to perform rescue operations (Search) when there is a reasonable belief that victims may be inside.
An interior structural fire (an advanced fire that has spread inside of the building where high temperatures, "heat" and dense smoke are normally occurring) would present an "Immediately Dangerous to Life or Health" (IDLH) atmosphere and therefore, require the use of respirators.
There should always be at least two firefighters together when they enter a location that is deemed a hazard area that is considered IDLH (i.e., the interior of the structure fire).
It also does not prohibit firefighters from entering a burning structure to perform rescue operations when there is a reasonable belief that victims may be inside.
Until those persons arrive on the scene, fire fighters may fight the blaze from outside the structure and carry out rescue activities.
When a team enters an IDLH atmosphere (the "two-in"), two more firefighters (the "two-out") stand by at the entrance in full personal protective equipment (to include bunker gear and self-contained breathing apparatus), and ready with rescue tools, in order to rapidly enter the building if the team inside becomes endangered.
However, the rule specifically exempts an emergency rescue with fewer personnel on hand (i.e., no additional "two-out" required if they go in to find the "two-in"), although the increased risk to all four should be obvious if further backup is not on-scene.
Until 1999, the firefighting in France was performed according to the "Rules of instruction and maneuvers" (Règlement d'instructions et de manoeuvres, RIM).
This organisation was generalised to the whole France in a departmental order signed by the minister of Internal Affairs the 3 February 1999.
German fire services regulations (FwDV) demand that firefighters must always operate in teams of two, called a Trupp; and that an interior attack with breathing apparatus may only be undertaken if there's at least a Staffel on scene, which consists of six firefighters: two Trupps, a commander, and an engineer.