(1) "Immediately dangerous to life or health" or "IDLH" means an atmosphere that poses an immediate threat to life, would cause irreversible adverse health effects, or would impair an individual's ability to escape from a dangerous atmosphere.
(2) "Interior structural fire fighting" means the physical activity of fire suppression, rescue or both, inside of buildings or enclosed structures which are involved in a fire situation beyond the incipient stage.
(3) "Self-contained breathing apparatus" or "SCBA" means an atmosphere-supplying respirator for which the breathing air source is designed to be carried by the user.
(b) In all atmospheres that are immediately dangerous to life or health, the fire department or company shall ensure that:
(1) One or, when needed, more than one firefighter, is located outside the IDLH atmosphere;
(2) Visual, voice or signal line communication is maintained between all firefighters in the IDLH atmosphere and those outside the IDLH atmosphere;
(3) All firefighters located outside the IDLH atmosphere are trained and equipped to provide effective emergency rescue;
(4) The fire department or company, or designee authorized by the fire department or company, is notified before any firefighter located outside the IDLH atmosphere enters the IDLH atmosphere to provide emergency rescue;
(5) Once notified, the fire department or company, or designee authorized by the fire department or company, provides necessary assistance appropriate to the situation;
(6) All firefighters located outside the IDLH atmospheres are equipped with:
Pressure demand or other positive pressure self-contained breathing apparatus or a pressure demand or other positive pressure supplied-air respirator with an auxiliary SCBA, and either:
(A) Appropriate retrieval equipment for removing all firefighters who enter IDLH atmospheres where retrieval equipment would contribute to the rescue of the firefighters and would not increase the overall risk resulting from entry; or
(B) Equivalent means of rescue where retrieval equipment is not required or not available.
(c) In addition to the requirements set forth under subsection (b) of this section, when firefighters are engaging in interior structural fire fighting, the fire department or company shall ensure that:
(1) At least two firefighters enter the IDLH atmosphere and remain in visual or voice contact with one another at all times;
(2) At least two firefighters are located outside the IDLH atmosphere; and
(3) All firefighters engaged in interior structural fire fighting use an SCBA.
(d) Nothing in this section is meant to preclude:
(1) The assignment of one of the firefighters located outside the IDLH atmosphere to an additional role, such as incident commander in charge, emergency officer or safety officer, so long as this firefighter is able to perform assistance or rescue activities without jeopardizing the safety or health of any firefighter working in the IDLH atmosphere; and
(2) The performance of emergency rescue activities by firefighters before an entire team has assembled.