In firefighting, the policy of two-in, two-out refers to United States Occupational Safety and Health Administration policy 29 CFR 1910.134(g)(4)(i) that mandates that firefighters never go into a dangerous situation in a fire or rescue incident alone, and that there be two firefighters outside the hazard area to initiate a rescue of the firefighters inside, should they become in trouble, during the initial stages of the incident where only one crew is operating in the hazard area. Once a second crew is assigned or operating in the hazard area, the incident is no longer considered in the initial stages and a dedicated firefighter assist and search team or rapid intervention crew is required.
There should always be (at least) two firefighters together when they enter a location that is considered a hazard area that is considered "Immediately Dangerous to Life or Health" (IDLH), i.e., the interior of the structure fire. Firefighters operating in the hazard area must operate in a buddy system and maintain voice or visual contact with one another at all times. This assists in assuring accountability within the team. They must operate together as a team the entire time they are in the hazard area. At no time, under any circumstances are they permitted to separate from one another. If one firefighter has to exit the hazard area, for any reason, such as their air supply getting low, they must both exit.
OSHA requires that one of the two firefighters outside must be dedicated to accounting for the two firefighters inside, and, if necessary, initiate a fire fighter rescue. The other firefighter is permitted to take on other roles, such as incident commander in charge of the emergency incident, safety officer or equipment/pump operator. However, the second firefighter outside cannot be assigned tasks that are critical to the safety and health of any other employee working at the incident.
These rules also apply to all training with live fires inside structures, and are even more important when inexperienced trainees are inside.
Exception for immediate action (OSHA)
Emergency rescue activities can be performed prior to assembling an entire team, without violating this section of the regulations, under 29 CFR 1910.134(g), Note 2. Responders may still be limited by local safety procedures, by command, and by the exercise of reasonable prudence under the circumstances.
Rapid intervention crew
The National Fire Protection Association (NFPA) defines the policy that refers to a safety system to protect firefighters, known as rapid intervention crew (RIC) or firefighter assist and search team (FAST), where two or more firefighters enter a building and at least two more remain outside, near the entrance, fully equipped and ready to help in case of emergency. Firefighters enter a building in teams to extinguish the fire and/or make a rescue. 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. By some interpretations, the rule requires at least two more firefighters to remain outside, even when the standby team has gone in to find and rescue the first team. 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.
The two firefighters who are specifically designated as standing by outside are referred to in different ways by many localities. The NFPA designated term is "RIC"., some also referred to as a rapid intervention team, while others are referred to as a F.A.S.T. truck (as in the Fire Department of New York).
Where there are teams working inside multiple entrances of a large structure fire, there may be standby teams designated at each entry point, although the rule does not necessarily mean two firefighters ready outside for every two inside.
Other tactics work within the rule to "stage" the next team, ready to relieve the inside team when their air supplies run low. When the third team arrives to serve as the RIT, the second team enters, follows the hose line to the first team and relieves them. This is naturally smoother with good radio communications between officers.
Application in France
Until 1999, the firefighting in France was performed according to the "Rules of instruction and maneuvers" (Règlement d'instructions et de manoeuvres, RIM). The firefighters acted in teams of three members, called "trinomial" (trinôme): one chief, one deputy chief and one support; a fire engine with eight people thus had two trinom, an engine chief (chef d'agrès) and a driver. In the 1990s, the Paris Fire Brigade started to work with teams of two people, called "binomial teams" (équipes en binôme) or shortly "binomials" (binômes). This organisation was generalised to the whole France in a departmental order signed by the minister of Internal Affairs the 3 February 1999. An engine with eight people now has three binomials, an engine chief and a driver; an engine with six people has two binomials, an engine chief and a driver.
A binomial can be assigned two types of missions:
- exploration and attack mission (binôme d'attaque, BAT);
- water supply and support mission (binôme d'alimentation, BAL).
The mission can change during an intervention, i.e., an attack binomial can become a supply binomial or vice versa.
The "usual" intervention (simple fire with only one fire engine and six people, no casualty, no specific risk) thus involves two binomials.
- The engine chief makes a reconnaissance with an attack binomial. The other binomial stands by outside, ready to help the reconnaissance team.
- The attack binomial unrolls the fire hoses at the "attack point" defined by the engine chief and prepare to go to the target also defined by the engine chief. The supply binomial joins the attack point to the fire engine with hoses.
- The attack binomial starts the firefighting. The supply binomial joins the fire engine to the hydrant.
- The supply binomial stands by, ready to help the attack binomial.
The overall organisation is the same when more engines are involved.
- "OSHA 29 CFR 1910.134(g)(4)(i) Procedures for interior structural firefighting". Occupational Safety and Health Administration.
- "NFPA 1500: Standard on Fire Department Occupational Safety and Health Program 2013 Edition". National Fire Protection Association. Retrieved 30 Jan 2013.