Naval Sea Systems Command
Basic Operation of the Open-Circuit SelfContained Breathing Apparatus (SCBA)
SCOTT Air-Pack 4.5
SCBA Issues
- SCBA Upgrades, Changes and Options
- Technical and Operational Information
- Carbon Fiber vs. Fiberglass
- Flash Hood Interface
SCBA Upgrades, Changes and
Cricket Alarm
Exhalation Valve
4 Strap Head Harness
Black Harness Material
Spectacle Kit
Carbon Fiber Cylinder
Chemical canister
Nearly 100% O2 delivered
to face piece
No positive pressure
Deflation of breathing bag
Positive pressure
approved as required by
Compatible with
equipment used by most
contemporary FF orgs
In conjunction with
BACS, can recharge in
60 sec while user is
still breathing on
SCBA: cylinder-fed, open circuit, provides
breathable air to fire fighter
Replacement for A-4 OBA
Principles of Operation
SCBA Components and
Component Parts
Air Cylinder and Valve Assembly
Holds 4500 psi compressed air
Fully wrapped composite construction
Breathing quality air (Grade D) not oxygen
Only durations of 30 and 45 minutes are used by Navy
Stored in lockers throughout ship on SCBA backpack
and as spares
15 year service life, requires hydrostatic testing
every 3 years
Label contains manufacturer’s name, date of
manufacture, hydrostatic test information and DOT
exemption number
Air Cylinder and Valve Assembly (Cont’d.)
DOT Exemptions:
Carbon Fiber
Air Cylinder and Valve Assembly (Cont'd.)
Located at neck of cylinder
Open and back off ¼ turn
Connection: CGA-347 (standard for breathing air
in the pressure range of 3000-5000 psi)
Burst disc: actuates when pressure inside air
cylinder reaches about 7200 psi
Air Cylinder and Valve Assembly (Cont'd.)
Pressure Indicator
Located on valve assembly at neck of cylinder
Provides continuous indication of air cylinder
Does not require calibration (shall not have “No
Cal Required” sticker)
Air Cylinder and Valve Assembly (Cont'd.)
Cylinder Hang Plate
Located on valve assembly at neck of cylinder
Provides mechanism for securing air cylinder to
SCBA backpack
Backpack and Harness Assembly
Corrosion resistant wire frame and cylinder hook
(mates to cylinder hang plate)
Backpack and Harness Assembly (Cont'd.)
Cylinder Band and Latch Assembly
Adjustable band and latch that secures air
cylinder to backpack
Fine adjustment can be made using vernier
adjustment while toggle lever is open (proper
adjustment = not able to turn with finger
pressure when latched)
Backpack and Harness Assembly (Cont'd.)
Harness Assembly
Consists of two adjustable shoulder straps and
an adjustable waist strap with pads
Waist belt has quick-release buckle and adjusters
and houses holder for second stage regulator
Shoulder straps have pull up, push-to-release
adjusters for quick adjustment
Flame and heat resistant Kevlar
Backpack and Harness Assembly (Cont'd.)
Remote Pressure Indicator
Located in front on right side shoulder strap
When air cylinder valve is open, provides
continuous remote indication of air cylinder
Face is fully luminescent
Does not require calibration (shall not have “ No
cal Required” sticker)
Backpack and Harness Assembly (Cont'd.)
Bell Alarm (Cricket Alarm)
Located in front on left side shoulder strap
When air cylinder pressure is at 23-27% of
capacity, will provide a steady dinging sound to
audibly alert the user of the situation
Backpack and Harness Assembly (Cont'd.)
High Pressure Hose
Located between cylinder valve and First-Stage regulator
(“pressure reducer”)
Delivers air at cylinder pressure to the First-Stage regulator
Hose is attached to air cylinder valve by the coupling nut.
The high pressure seal is made by the coupling nut o-ring.
Before disconnecting the coupling nut, ensure all air
is bled from the high pressure hose. Air left in the
hose m ay cause the o-ring to dislodge, resulting in
inability to m ak e a seal.
First-Stage Regulator
(Pressure Reducer)
First-Stage Regulator
(Pressure Reducer) (Cont'd.)
First-Stage Regulator
Mounted to the left of the air cylinder
Reduces cylinder pressure to about 100 psi
Uses a redundant dual path reducing system;
secondary path automatically supplies air if
primary path fails
First-Stage Regulator
(Pressure Reducer) (Cont'd.)
Pressure Relief Valve
Located on the side of the First-Stage regulator
Reseatable relief valve; actuates above 185 psi
First-Stage Regulator
(Pressure Reducer) (Cont'd.)
Quick Charge Assembly
Located adjacent to the waist strap on the left
side of the wearer
Air cylinder refillable without removing the air
cylinder and while continuing to breathe on the
Second-Stage Regulator
(EZ-Flow Regulator)
Low Pressure Hose
Located between pressure reducer and second
stage regulator
Provides pressure of ~100 psig to second stage
Second-Stage Regulator
(EZ-Flow Regulator) (Cont'd.)
Located at the end of the low pressure hose and
connects to the face piece
Demand regulator maintains a positive pressure
in the face piece at all times
If face piece or seal is broken, air will flow freely
from regulator
Second-Stage Regulator
(EZ-Flow Regulator) (Cont'd.)
Purge Valve
Red knob located on the left side of regulator (as
viewed when wearing)
Purge valve manually overrides the Second-Stage
Provides a constant flow of air to the face piece
Used for em ergencies only; ex it space
im m ediately if breathing w ith purge valve
Can also be used to clear fogging in face piece
Rotate handle ccw (away from wearer) to open
Second-Stage Regulator
(EZ-Flow Regulator) (Cont'd.)
Air Saver Switch
Black button on top of regulator
Stops air flow from the Second-Stage regulator
Press and release to actuate
Inhale sharply to disengage
Second-Stage Regulator
(EZ-Flow Regulator) (Cont'd.)
Removal Lever
Black tab on right side of regulator
Used to“unlock” Second-Stage regulator from
face piece in order to remove it
To use, push tab away face and hold while
Second-Stage Regulator
(EZ-Flow Regulator) (Cont'd.)
“Vibralert” Alarm Assembly
Housed within the Second-Stage regulator
Alarm will sound when 20-25% of cylinder air
Alarm will also activate to indicate a problem in
the First-Stage regulator
Face Piece
Face Piece
Face Seal
Available in three sizes: small (green), large
(black), and Xlarge (red)
Made of a blend of natural and synthetic rubber
Face Piece (Cont'd.)
Single, replaceable, wide angle, clear lens
Made of polycarbonate with a silicone-based
coating to resist abrasion and chemical attack
Face Piece (Cont'd.)
Head Harness
Connected to the face piece by quick adjusting
buckles and snap retainers
Made of synthetic rubber
Face Piece (Cont'd.)
Voice Amplifier
Located in a mounting bracket over the right side
Powered by one 9-volt battery
SCBA Donning Procedure
SCBA Donning Procedure (Cont'd.)
Inspect SCBA:
quick visual inspection for any
obvious damage that would
preclude safe and proper use
of the SCBA
SCBA Donning Procedure (Cont'd.)
Inspect Face piece:
Inspect Head Harness:
or missing;
Inspect Lens:
rubber deterioration, cracks,
tears, holes, tackiness
breaks; missing straps; loss of
elasticity; buckles
corroded, damaged
strap serrations worn
cracks, scratches, loss of
tightness to face piece, regulator
inlet coupling deformed or
SCBA Donning Procedure (Cont'd.)
Inspect Backpack:
cuts, tears, abrasions, signs
of chemical or heat damage,
inoperative buckles, damage
to wire frame
SCBA Donning Procedure (Cont'd.)
Inspect Cylinder:
minimum pressure allowed is
4000 psi; check cylinder for
charring, dents, gouges or
cuts that may have
penetrated fiberglass or
carbon fiber
SCBA Donning Procedure (Cont'd.)
Inspect Hoses:
cuts, cracks, abrasions, bulges,
wrinkles, loose or inoperative
SCBA Donning Procedure (Cont'd.)
EZ-Flow Regulator
Check casing for damage, dirt or debris
Actuate purge valve, air saver switch
and removal lever
Check sealing gasket
SCBA Donning Procedure (Cont'd.)
Don SCBA (coat method or over-the head)
Most of the weight (85%) should be carried
on the waist/hips
Check all straps for correct adjustment
SCBA Donning Procedure (Cont'd.)
Don Face Piece
Spread face piece straps from inside with
Place chin in chin cup
Pull harness over head and smooth straps
Ensure all hair is away from seal
Tighten neck straps first, then temple straps
SCBA Donning Procedure (Cont'd.)
Perform Negative Pressure Check
Place hand over face piece opening for second
stage regulator
Inhale and hold your breath
Listen/feel for inward air leakage
Adjust face piece as needed until seal is
SCBA Donning Procedure (Cont'd.)
Open Air Cylinder Valve
First depress air saver switch
Ensure purge valve is closed,
Open cylinder valve, close ¼ turn, and listen for
Vibralert to sound during initial equalization (the
bell alarm may or may not sound at this time)
SCBA Donning Procedure (Cont'd.)
To Begin Operation (“go on air”)
Attach Second-Stage regulator to face piece lock
in place
Inhale sharply to begin flow of air
Breathe with purge valve open to experience
breathing in free flowing air
Close the purge valve, press air saver switch and
disconnect regulator from face piece
Wait to engage the air saver switch until just prior
to pulling the regulator away from the mask
Breathing Air Replenishment
Breathing Air Replenishment
Air Cylinder Change-out
Assume leaning rest position
Assistant closes air cylinder valve
Wearer bleeds system through purge valve and
stows regulator in waist clip
Assistant disconnects air cylinder coupling nut,
unsnaps toggle latch & lever and locking tab and
removes cylinder (Grasp cylinder valve
securely while doing this!!!)
Breathing Air Replenishment
Air Cylinder Change-out (Cont'd.)
Assistant obtains full cylinder and announces cylinder
pressure to wearer
Assistant replaces full cylinder on backpack making
sure it is secure
The cylinder may easily be installed by running the
cylinder up through the bottom of the cylinder band
Check coupling nut o-ring
Attach hose
Open air cylinder valve (back ¼ turn)
Check for leaks
Verify air pressure on remote indicator
Breathing Air Replenishment
Quick Charge
BACS operator will:
* inspect cylinder and backpack
* remove dust cap from quick charge
couplings and inspect couplings for dirt or
* grasp hose below coupling and push couplings
together until QDs click
Air flow starts automatically; monitor pressure
increase on remote gauge
Air flow stops automatically when cylinder is full
Breathing Air Replenishment
Quick Charge
BACS operator will:
- disengage quick charge coupling
- reinstall dust caps on both couplings
- ensure quick charge hose is attached firmly
to harness before dismissing SCBA wearer
SCBA Doffing Procedure
Ensure purge valve is closed, press air saver
Disconnect regulator from face piece
Close air cylinder valve
Bleed air from system through purge valve and
stow Regulator in waist clip
Doff SCBA using coat method (Do not hold by
the hoses)
Perform MRC R-1 and R-2 after each use (R-1
refers to M-1 which is in-depth inspection of unit.
Read/perform M-1 with students.)
SCBA Doffing Procedure
Mix 2 tablespoons of Wescodyne G in a pail
containing 1.5 gallons of water not to exceed
temperature of 110°F
Prepare two more buckets containing 2 gallons of
fresh water each. Temperature should not exceed
Agitate each face piece for 15 seconds with a total
immersion time of 2 minutes in the bucket containing
Agitate each face piece for 15 seconds in each of the
buckets containing the fresh water rinse
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