SEFA
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The SEFA is a make of backpack industrial breathing set formerly made by Sabre Safety. It is an oxygen rebreather. "SEFA" is an acronym for "Selected Elevated Flow Apparatus".
[edit] Description
It is in a shiny backpack stainless steel sheet casing with rounded corners and edges, 16 inches wide, 21½ inches high, 6½ inches front to back. It has two wide corrugated breathing tubes leading to a fullface mask which has an inner ori-nasal mask and a front panel for talking through.Its breathing tubes are 22 inches long, and face forwards as they come off the backpack casing.
Its use duration on a filling is 2 hours. It does not have a demand valve or electronic parts, and thus not so much to go wrong. It is not designed for scuba diving, but can be used for short shallow submersion as in going through short flooded sections of underground passages. Its casing, to keep grit and stones out of its working, is completely sealed, except for a large vent panel covered with metal mesh, and holes for the oxygen cylinder's on/off valve and the cylinder pressure gauge. Its oxygen flow can be set to 5 or 10 liters/minute. Its intended absorbent is a special make called SefaSorb, which is mostly calcium hydroxide.
The absorbent makes the breathing gas in circuit hot as it absorbs carbon dioxide. To try to get rid of that heat, there is a device to pass the breathing gas through a damp chamber, so it will absorb some heat as it evaporates, as in some air conditioning units.
[edit] History
It was being designed from 1985 onwards in response to demands from the British coal mining industry for a new make of mines rescue breathing set with longer duration for bulk than an open-circuit set. They were made from 1989 to 2004. Making them stopped because of declining demand because of the decline of the British coal mining industry. They are no longer official issue because of lack of availability of spare parts. The British coal industrty, when needing rebreathers, now uses a German rebreather made by Draeger.
[edit] Not for scuba diving
It is not intended for scuba diving, because:-
- It is not designed to resist seawater corrosion.
- When a diver with a SEFA comes out of the water, a large pool of water would be held in the bottom of its casing, due to lack of a bottom drain hole.
- The usual hazards of oxygen rebreather diving would apply.
[edit] Images
When photographed these sets were being used without their internal parts during a demonstration of rescue techniques in open air without any gas hazard in the area.
 5 SEFAs seen from top and front |
 2 SEFAs seen from the right side |
 4 SEFAs seen from the back |
 Man in boilersuit wearing a SEFA, seen from the side |
