OSHA 2 In / 2 Out

OSHA’s “2 In / 2 Out” Regulation

The “2 In/2 Out” policy is part of paragraph (g)(4) of OSHA’s revised respiratory protection standard, 29 CFR 1910.134.  The safety of firefighters engaged in interior structural firefighting is the major focus of paragraph (g)(4) of the OSHA Respiratory Protection standard. The regulation  is quoted at the right.



OSHA’s interpretation on requirements for the number of workers required being present when conducting operations in atmospheres that are immediately dangerous to life and health (IDLH) covers the number of persons who must be on the scene before firefighting personnel may initiate an interior attack on a structural fire.  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 IDLH atmosphere and, therefore, require the use of respirators.  In those cases, at least two standby persons, in addition to the minimum of two persons inside needed to fight the fire, must be present before firefighters may enter the building.[1], [2]  This requirement is mirrored in NFPA 1500, which states that “a rapid intervention team shall consist of at least two members and shall be available for rescue of a member or a team if the need arises.  Once a second team is assigned or operating in the hazardous area, the incident shall no longer be considered in the ‘initial stage,’ and at least one rapid intervention crew shall be required.”

[1] Under the NFPA standards relating to firefighter safety and health, the incident commander may make exceptions to these rules if necessary to save lives.  The Standard does not prohibit firefighters from entering a burning structure to perform rescue operations when there is a “reasonable” belief that victims may be inside.

[2] Paula O. White, letter to Thomas N. Cooper, 1 November 1995 (OSHA)

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GIS Web-Mapping

The following shows the the area in which the 2 in / 2 out rule can be implemented within 4 minutes. The results are summarized in the table below.


Download the map in a printable PDF format.


Interpretting the Results

The 2 In / 2 Out response consists of at least 4 firefighters being assembled on-scene within 4 minutes in order to meet the OSHA requirements for interior structural firefighting. Currently, the Mansfield Fire Department is capable of initiating fire suppression and rescue operations in accordance with the “2 In/2 Out” Regulation on 48% of all City roads within 4 minutes or less, assuming all units are available to respond immediately upon dispatch. The following output table indicate the 4 minute coverage breakdown by each Engine company district:


Table 1: 2 In/ 2 Out 4 Minute Coverage – Current Deployment and Organization

Fire District

Total Street Length (ft)

Total Streets Covered in 4 Minutes (ft)

% of Streets Covered in 4 Minutes


























The preceding table indicates that the current model is grossly below the safety standard, namely for one major reason. Under the current deployment, Engine 4 and Engine 6, both staffed with 3 firefighters, must wait for an additional apparatus to arrive and assemble prior to initiating an attack according to the OSHA safety regulation. Conversely, Station 2 and Station 3, each with a total of 4 personnel, (2 Engine Company personnel and 2 Rescue Squad Personnel) can implement the rule if both units are fully staffed and in station at the time of call.


The Importance of Implementing the 2 In / 2 Out Rule within 4 Minutes

Two of the most important elements in limiting fire spread are the quick arrival of sufficient numbers of personnel and equipment to attack and extinguish the fire as close to the point of origin as possible, as well as rescue any trapped occupants and care for the injured.  Several existing National Fire Protection Association standards address this time-critical issue.  NFPA 1500 states, “while members can be assigned and arrive at the scene of an incident in many different ways, it is strongly recommended that interior fire fighting operations not be conducted without an adequate number of qualified firefighters operating in companies under the supervision of company officers.  It is recommended that a minimum acceptable fire company staffing level should be four members responding on or arriving with each engine and each ladder company responding to any type of fire.”  NFPA Standard 1710 further recommends that “fire companies whose primary functions are to pump and deliver water and perform basic fire fighting at fires, including search and rescue… shall be staffed with a minimum of four on-duty personnel,”[1] while “fire companies whose primary functions are to perform the variety of services associated with truck work, such as forcible entry, ventilation, search and rescue, aerial operations for water delivery and rescue, utility control, illumination, overhaul and salvage work… shall [also] be staffed with a minimum of four on-duty personnel.”[2] 


There exist a number of incidents in which the failure to follow “2 In/2 Out” procedures have contributed to firefighter casualties.  For example, in Lexington, Kentucky, one firefighter died and a second was severely injured following a fire where Kentucky OSHA later cited the firefighters' employer for failing to utilize “2 In/2 Out” procedures.  In a second case, two firefighters died from smoke inhalation after being overcome by toxic fumes while fighting an accidental fire in Philadelphia, PA.  Although two additional firefighters were outside the home, both were engaged in support activities (hydrant hook-up and pump operation), and neither was fully accountable for monitoring the interior personnel.


There also exist a number of success stories following the adoption of “2 In/2 Out” procedures.  In Pittsburgh, PA, the Fire Department implemented an accountability and rescue system following a fatal fire.  In one instance, four firefighters who were performing an interior attack on an apartment building fire became disoriented and were trapped in the building.  The standby personnel were able to initiate rescue operations promptly and, although the four interior firefighters and two of the rescuers were injured, all survived.[3]


It warrants emphasizing that the ability of the Fire and Rescue Service to assemble a sufficient number of firefighters to initiate “2 In/2 Out” fire suppression and rescue activities occurs within 4 minutes.  It is very likely that the first-in company may arrive in significantly less than 4 minutes, and the second-in company may arrive closer to the 8-minute mark.  This lag time between the arrival of units is significant in that if staffed with less than four firefighters, fire companies are completely unable to perform fire and rescue operations in accordance with the “2 In/2 Out” regulation.


OHSA 2 In/ 2Out Illustrated”


When confronted with occupants trapped in a burning structure and a single fire company is on scene, only a company staffed with four firefighters is able to initiate emergency search and rescue operations in compliance with “2 In/2 Out” operations.  As indicated in the previous graphic, this requires the complete engagement of every firefighter from the first-in fire company, staffed with four, to participate in the effort, and means that the driver-operator of the apparatus will not be able to tend to the pump to ensure the delivery of water to the firefighters performing the initial attack and search and rescue operations.


Regardless, when there exists an immediate threat to life, only a company of four firefighters can initiate fire suppression and rescue operations in compliance with the “2 In/2 Out” regulation, and in a manner that minimizes the threat of personal injury.  In all other instances with a four-person fire company (i.e., when there is not an immediate threat to life), the first-in company must wait until the arrival of the second-in unit to initiate safe and effective fire suppression and rescue operations. This condition underlines the importance and desirability of fire companies to be staffed with four firefighters, and stresses the benefit of four-person companies and their ability to save lives without the delay in waiting for the second-in company to arrive.


“2 In/2 Out,” Flashover, & Fire Operations:

Only those structure fires located within a limited area, as depicted in the preceding web map, where a sufficient number of personnel arriving on appropriate apparatus can arrive at a common destination within 4 minutes, will receive the equipment and personnel required to initiate safe and effective fire suppression and rescue operations in accordance with the OSHA and NFPA guidelines outlined in this report.  As the progression of a structural fire to the point of flashover generally occurs within 4 to 10 minutes, it is predicted that those structure fires at the furthest reaches and beyond the extent of the 4-minute polygons indicated in these maps are more likely to continue to burn up to and beyond the point of flashover.


NFPA 1500 and 1710 both recommend that a minimum acceptable fire company staffing level should be four members responding on or arriving with each engine and each ladder company responding to any type of fire.  Recall, however, that at the scene of an emergency, the driver/operator of the engine must remain with the apparatus to operate the pump.  Likewise, the driver/operator of the ladder truck must remain with the apparatus to safely operate the aerial device.  Such activities, which help to ensure the safe and effective delivery of fire suppression and rescue services, leave a crew of only three to two firefighters from an engine company to support the attack or complete search and rescue activities.  Due to the demands of fire ground activities which reduce the effective firefighting force deploying from each company from four or three firefighters to three or two (respectively), a fire attack initiated by a single fire company is not capable of effecting a safe and effective fire suppression and/or rescue operation in compliance with the “2 In/2 Out” regulation until a second company arrives with sufficient personnel to support the fire attack and/or rescue operation, and to assist the first company in the event of an unexpected emergency.[4]  Industry studies have confirmed that four firefighters are capable of performing the rescue of potential victims faster than a crew of three firefighters.[5]

[1] NFPA 1710, § and §

[2] NFPA 1710, § and §

[3] John B. Miles, Jr., letter to J. Curtis Varone, Esq., 29 April 1998 (OSHA)

[4] Recall that a four-person fire company may initiate emergency search and rescue operations at the order of the incident commander if there is a “reasonable” and immediate threat to life.

[5] McManis Associates and John T. O’Hagan & Associates, Dallas Fire Department Staffing Level Study, (June 1984); pp. 1-2 and II-1 through II-7; Richard C. Morrison, Manning Levels for Engine and Ladder Companies in Small Fire Departments, (1990)