escape respirator

Applications

Escape breathing apparatus are a class of self contained atmosphere supplying or air purifying breathing apparatus for use in emergencies, intended to allow the user to pass through areas without a breathable atmosphere to a place of relative safety where the ambient air is safe to breathe. These are ambient pressure systems, and include:

Helicopter escape set

Mine escape set

Submarine escape set

Amphibious Tank Escape Apparatus

Smoke hood

Railroad tunnels used by diesel locomotives

Early escape sets were often rebreathers and were typically used to escape from submarines that were unable to surface. Escape sets are also used ashore, in the mining industry, and by the military for escape from tanks.

The small open-circuit scuba Helicopter Aircrew Breathing Device has the similar purpose of providing breathing gas to escape from a ditched helicopter.

Selection

Escape breathing apparatus have the function of allowing a person working in an environment that is normally safe, enough time to escape from respiratory hazards that may occur without sufficient warning to evacuate without respiratory protection. Therefore, selection relies mainly on the time required to escape, and the probability of IDLH or oxygen deficiency, rather than assigned protection factors.

Calculation of the time likely to be needed for escape and the recommended escape route is the responsibility of the employer, and should take into account the reasonably foreseeable emergencies that might require escape.

An air purification type escape respirator includes a filter or absorbent cartridge suitable for the environment in which it is intended to be used. They are unsuitable for escape through potentially oxygen depleted environments. An escape respirator that provides autonomous gas will allow the user to escape most environments that require only respiratory protection. They are generally available with endurance ratings from 3 to 60 minutes. 10 and 15 minutes are common specifications. An escape respirator provides no chemical or environmental protection to the rest of the user's body, and the need for eye protection must be considered when choosing the user respiratory interface.

Types

Autonomous breathing gas supply

These breathing apparatus carry a supply of breathing gas calculated to be sufficient for most users to escape within the specified time-frame.

Atmospheric air contains about 21% oxygen. In normal breathing the body uses about 4% and replaces it with carbon dioxide. A volume of air can be breathed several times before its oxygen content is exhausted, but carbon dioxide accumulates as the oxygen is used up, and causes discomfort and respiratory distress, so it must be removed from the breathing cycle. There is also a danger that when the oxygen level is too low, the user will lose consciousness due to hypoxia, and may asphyxiate, so oxygen must be provided to compensate for use.

The absorbent used for non-regenerative carbon dioxide absorption is usually sodalime, or a material based on sodalime, but in former times slaked lime or quicklime or caustic soda was sometimes used.

Rebreathers using chemical oxygen generation can be small, light and easy to wear. They may use the pendulum type breathing system, which has larger dead space than a one-way loop architecture, but is simpler and cheaper to manufacture. Endurance is generally from 20 to 100 minutes Oxygen is produced by a chemical reaction between the carbon dioxide and potassium superoxide absorbent, which both removes the carbon dioxide and supplies a slightly larger volume of oxygen to replace that which was used.

A basic unit may use a bite-grip mouthpiece and nose clip, or may include goggles or a hood if eye protection is necessary. Some units have a cartridge to inflate the bag when first used, but this is mainly to provide a bit more volume in the counterlung, which can reduce the feeling of insufficient gas at startup when the bag is nearly empty.

These sets can offer a relatively long endurance, and may be classed as working breathing apparatus as well, in which case they may be worn to carry out a task, unlike most escape sets which are for escape only. The endurance times are affected by exertion. Harder work increases oxygen usage and carbon dioxide production, both of which use up the chemicals in the scrubber. The gas delivered can be fairly hot and may be uncomfortable to breathe in a hot environment. The sets are usually made for one use only so activation for false alarms or misuse can be costly. Some users may have a gag reflex from the mouthpiece. Potassium superoxide is violently reactive in contact with water, and could be dangerous for escape sets which may leak while immersed.

Continuous-flow Escape-SCBA

A continuous-flow self-contained breathing apparatus (SCBA), usually with hood, is a type of emergency escape breathing apparatus.

Certification

Escape respirators should be certified by a national authority analogous to the United States' National Institute for Occupational Safety and Health (NIOSH) for use in the atmosphere types for which the respirator is intended. Some standards apply to the level of protection for the user, and others relate to the intrinsic safety of the equipment for use in flammable and potentially explosive atmospheres. Some standards are voluntary, going above the minimum requirements of a national authority such as NIOSH. Conformance with voluntary standards may be shown through third-party product certification such as those issued by the Safety Equipment Institute (SEI).

Depending on the industry in which they are used, escape respirators may have to comply with, or be approved in terms of, one or more of:

ASTM E2952-23 — Standard Specification for Air-Purifying Respiratory Protective Smoke Escape Devices (RPED)

NFPA 1981-19 — Standard on Open-Circuit Self-Contained Breathing Apparatus (SCBA) for Emergency Services

NFPA 1984-22 — Standard on Respirators for Wildland Fire-Fighting and Wildland Urban Interface Operations

NFPA 1986-23 — Standard on Respiratory Protection Equipment for Tactical and Technical Operations

NFPA 1987-23 — Standard on Combination Unit Respirator Systems for Tactical and Technical Operations

EN 402:2003 — Respiratory protective devices - Lung governed demand Self-contained open-circuit compressed air breathing apparatus with full face mask or mouthpiece assembly for escape.

ISO 23269-1:2008 — Ships and marine technology — Breathing apparatus for ships — Part 1: Emergency escape breathing devices (EEBD) for shipboard use.

History

Development of the first militarily useful submarines before the First World War raised the question about rescue and escape if the submarine was unable to surface. Robert Henry Davis and Henry A. Fleuss developed a rebreather, which was useful in the mining industry and under water.

One example is the Davis Submerged Escape Apparatus. Escape sets were also used ashore, e.g. in the mining industry, and for escape from tanks (Amphibious Tank Escape Apparatus).

1903: Siebe Gorman started to make this breathing set in England; in the years afterwards it was improved, and later was called the Davis Submerged Escape Apparatus.

1905: An important innovation: metering valves to control the supply of oxygen. This was promptly adopted by other companies which made escape sets.

1907: Draeger of Lübeck invented the U-Boot-Retter = "submarine rescuer".

Both systems were based on oxygen supply from a high-pressure cylinder with simultaneous absorption of carbon dioxide by an inserted cartridge filled with sodium hydroxide.

1916: The Draeger model DM 2 became standard equipment of the German Navy.

1926: Draeger displayed a rescue breathing apparatus that the wearer could swim with. While the previous devices served only for ascending to the surface and were designed also to develop buoyancy so that the wearer arrived at the surface without swimming movements, the diving set had weights, which also made it possible to dive down with it, to search and rescue after an accident.

1939: Hans Hass developed from the escape set a type of rebreather with its bag on his back and two breathing tubes but no backpack box. These sets appear much in his movies and books.

In popular media

Escape sets are used in these films:

Das Boot (Johann das Gespenst stops water from breaking in under a diesel engine)

Haie und kleine Fische (controlled exit from a sunk submarine)

In Enemy Hands (To survive a prolonged submersion while under attack by a destroyer)