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Equipment - Compressed Air Breathing Apparatus

The SA CFS uses Sabre Centurion Breathing Apparatus. The sets are Positive Pressure - indicating that the set maintains a higher pressure within the facemask than the surrounding atmosphere (approximately 6 millibar in this case), so that in the event of a leak or loss-of-seal, air will escape from the mask, rather than potentially harmful surrounding air leaking into the mask. They are Open Circuit - when breath is exhaled by the wearer, it leaves the the system through an exhalation valve located in the inner face mask. The sets supply air On Demand - as air is expelled from the mask, the Demand Valve replaces it with fresh air from the cylinder. During intense work, an operator is expected to use 40lpm, while the demand valve is capable of delivering 600lpm.

Both Aldgate 12 and Aldgate 24Pumper carry four sets of BA, along with four spare cylinders, allowing (attendance permitting) Aldgate to maintain eight BA operators at an incident.

A standard BA set incorporates the following items:

Sabre Centurion Breathing Apparatus
Aldgate 12 Locker 4:4
Aldgate 24Pumper Locker 6:2
Aldgate 24Pumper Locker 7:2

Each apparatus has the following components:

Backplate and Harness
Stainless Steel backplate, supposedly ergonomically designed, fully-adjustable harness includes lightly padded shoulder straps and waist belt.
Cylinder Valve Connection
Connects between the cylinder valve and the pressure reducer. Located at the bottom of the backplate, the normal right-handed-thread should only be finger tightened, after ensuring the 'O-ring' seal is in place and not damaged.
Pressure Reducer
Passes un-restricted air from the cylinder to the Pressure Gauge and Low Air Warning Whistle, and supplies low pressure air, restricted by means of a self-adjusting piston valve, to the Demand Valve.
When used in low ambient temperatures, the Pressure Reducer may ice-up, but will 'pop' open when air is passed through the system.
Pressure Gauge and Low Air Warning Whistle
The Pressure Gauge allows the monitoring of the actual cylinder contents while in use, by means of 10bar divisions reading up to a maximum 360bar. The first 40bar are the operator's "Safety Margin", and so are indicated with red. The dial face is coated with phosphorescent material.
The Low Air Warning Whistle emits a whistle sound when cylinder pressure has dropped below 50 (+/- 5) bar, using less than 5lpm. Once the whistle is audible, the operator should attempt to safely leave the incident and report to the ECO. At no time should the mask be removed from the wearer's face whilst in an incident (only the demand valve should be removed in case of cylinder exhaustion).
Demand Valve
The Demand Valve controls the flow of air into the facemask, at the same rate as air is expired air is expelled by the operator. The Sabre Centurion demand valve is First Breath Activated - it will not release any air until the operator has donned the face mask and breathed in, lowering the air pressure within the face mask. The First Breath Mechanism can be reset using the black button on the rear of the demand valve.
The Demand Valve also has a manual bypass valve, which releases a free supply of air into the face mask at around 130lpm. The demand valve should only be used in the event of demand valve failure, or to provide a quick supply of fresh, cool air to the operator in event of heavy exertion, or to defog the facemask.
Panaseal Face Mask
The masks stowed on Aldgate appliances are constructed from silicone, with a reflex seal which provides a firm seal to a clean-shaven face. The visor is made from impact resistant polycarbonate. There is an inner mask, which fits around the nose, mouth and chin of the operator. Fresh air is drawn into the inner mask by the natural breathing of the operator, and then exhaled air is expelled from the inner mask into the atmosphere through the exhalation valve. An aluminium speech diaphragm allows limited vocal communication by the wearer, but the sound is still difficult to interpret and is directed straight in front of the mask.
Air Cylinder
Aldgate Station Store Room:6
Aldgate 12 Locker 4:4
Aldgate 24Pumper Locker 6:2
Aldgate 24Pumper Locker 7:2

SA CFS operates hoop-wrapped FRP cylinders with a thick aluminium core. The cylinders have a water capacity of 9l, giving a nominal 1800l of air compressed to 200bar. The cylinders are bright green, with a green label. Cylinders have a maximum charging pressure of 207bar, and should not be used if they contain less than 80% (170bar) of air. Aldgate uses common Group cylinders, where by empty cylinders are replaced with filled ones at the Group Base (Bridgewater Station).

Distress Signal Unit
A DSU is attached to the lowest point of the left-hand shoulder strap of each BA set, and is activated when the Operator Tally is removed from the DSU and handed to the ECO when entering an incident. DSU's emit a loud, piercing distress signal when the operator remains motionless for more than 30 seconds. Initially Firefly K DSU's were supplied to the CFS, which use a ball-bearing running in a track with metal brush 'sensors' to detect movement. As there is no way to stop the ball from running, the ball continuously rolls around the track while the appliance they are stowed on is moving, wearing out the sensors. As the Firefly's become inoperable, they are being replaced by Super Pass II DSU's, which use infra-red to detect movement, and so will not wear out.
The DSU's have two levels of alarm - pre-alarm, activated after ~20 seconds of inactivity, and quiet warning signals, and full-alarm, activated after ~10 seconds of inactivity in pre-alarm, or manually. The full-alarm emits a loud, piercing high-pitch distress signal, and flashing red and yellow LED's, and will continue until the unit is manually reset.
Personal Line
~6m of 4mm braided cord is stored in a pouch on the right-hand waist belt. The line starts with a dog-clip, and is tethered at the first meter, which is used to maintain contact with another operator or a Main/Branch Line. The remaining 5m is freed by means of a frustratingly difficult to use press button, and is used to conduct a wide-area search.
The cord should be re-stowed by means of simply shoving the line into the pouch bit-by-bit - if the cord is rolled, it is likely it will knot when it is removed.
Personal Torch
Each set in use at the Aldgate CFS has a 2AA Mini-Maglite Incandescent Torch stowed in a pouch and secured by a short line to the right-hand shoulder strap. As well as providing limited illumination, the torch can be used to 'charge' the phosphorescent face of the Pressure Gauge.
When the pigs fly home to roost, the torches will hopefully be replaced by vastly superior - in terms of both light output and longevity - LED torches.

BA Control Board - Stage 1

The BA Board is used by the ECO to ensure the safety and control of BA operators at all incidents where operators are not under direct observation.
There is a BA Board stowed on each appliance; in a blue bag hanging behind the Passenger Seat in Aldgate 12, and in a red bag in Locker 6 on Aldgate 24Pumper.

Missing image of BA Board

BA Control Board from Aldgate 12

Using the BA Control Board:
The ECO should be situated in direct line-of-sight of the sole entry point. After checking the pressure on the guage (which must be above 170bar), retrieve the DSU tally and record the operator's name and pressure, then stow the tallies. Determine the lowest pressure of the team, and use it to determine the "Time Due Out":

  1. Line up the pressure mark (on the green half) with the current time mark (using the time on the BA Board clock, not the actual time)
  2. The arrow on the right-hand side of the slide lines up with a time mark in the next hour. Record this in the "Time Due Out" column for both operators.

The slide rule simplifies the following equation:

Missing image: Complete Equation: division of the product of the cylinder water capacity (9) and the difference of the current cylinder pressure and the safety margin (40) and the standard oxygen usage rate (40).

Which can be simplified to:

Missing image: Simplified equation: (9 x ([current cylinder pressure] - 40)) / 40

For example, consider a cylinder filled to the standard 200bar:

Missing image: Example equation: (9 x ((200) - 40)) / 40 = (9 x 160) / 40 = 1440 / 40 = 36 mins

Note, the slide rule gives the time due out for a cylinder filled to 200bar as 35mins. A list of standard durations are listed on the board:

  • 200bar => 35 mins
  • 190bar => 33 mins
  • 180bar => 31 mins
  • 170bar => 29 mins

Each BA Control Board has the following components:

Chinagraph Pencil
Made from coloured, hardened wax, the Chinagraph pencil will write on the acrylic face of the BA Board even when wet, and does not rub off easily. They also tend to break, a lot, so a pencil sharpener is stored in the PVC tube at the bottom of the board.
Clock
Used to calculate and monitor the "time due out" of BA operator pairs. Note that the set time is unimportant, only the difference in time is needed. If the clock is not working, substitute your pager, and ensure the time difference between pages is noted if swapping ECO's.
Slide Rule
The top green half of the slide is for standard 207bar 9lwc CFS cylinders. The bottom red half (for uncommon light fully-wrapped cylinders, such as stowed on Burnside HAZMAT) can be happily ignored.
Tally Slots
Both boards have room for 6 BA Tallies (attached to the DSU key). On the tally itself (not the Board), record the name of the operator, the gauge pressure (check yourself), and the time as displayed on the BA Board clock.
Time Due Out
Record the "Time Due Out" as calculated using the slide rule here.
Actual Time Out
Record the time the operator reported back to you here.
Location Remarks
Concise information on which area which the operators will be searching, which Main Guideline/Branchline they will follow, etc.
Spares Tube
An Aldgate Original, a 25mm PVC tube attatched to the bottom of the board, containing a Lumocolor pen (Chinagraph replacement, but only works in the dry), a spare Chinagraph pencil, and a pencil sharpener.

Staging Area Tarpaulins

Two PVC tarpaulins are stored with the BA sets, a green one, for setting fresh cylinders, sets, and any required equipment, and a red one, used for doffing BA, storing empty cylinders, and son on. The Staging Area should be set up in line of sight and near the entry point (but not too close), upwind, and preferably in the shade.

Main Guideline / Branchlines

Stored with the BA Sets on both Appliances are "Guidelines", 60m of 10mm thick plaited cotton cord, with a dog clip each end, stuffed into a canvas container. They are used (at the discretion of the OIC) to allow BA operators to tie a path which they (and subsequent crews) can follow, increasing personal safety and search efficiency. Rarely used, they are only really bothered with if a search of a smoke-logged school or hospital needs to be performed.
Stored with the tallies, which are either a yellow disk printed with "A" or "B" used to identify a Main Guideline, or a yellow rectangle with 1, 2, 3, or 4 holes cut into them to identify Branchlines.
The use of Guidelines and Tallies will be conducted by trained personnel.

 
22/06/2011
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