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BREATHING APPARATUS

Presentation by Mustafa AKMAN, 167987

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CONTENTS

What is BA ?

Types of BA: Open Circuit, Close Circuit

Parts of BA

Preparation - Usage

Inspection of BA

How does it work ?

Charging cylinders

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WHAT IS BA ?

A self contained breathing apparatus (SCBA), or simply BreathingApparatus (BA) is a device worn by rescue workers, firefighters, andothers to provide breathable air in an IDLH (Immediate Danger to Lifeand Health) Atmosphere. The term "self-contained" means that thebreathing set is not dependent on a remote supply ( e.g. , through a long

hose). If designed for use under water, it is called SCUBA ( self-contained underwater breathing apparatus).

An SCBA typically has three main components: a high-pressure tank (e.g., 2200 psi to 4500 psi), a pressure regulator , and an inhalationconnection (mouthpiece, mouth mask or face mask), connectedtogether and mounted to a carrying frame.

There are two kinds of SCBA: open circuit and closed circuit .

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CLOSE CIRCUIT

The closed-circuit type filters, supplements,and recirculates exhaled gasIt is used when a longer-duration supply ofbreathing gas is needed, such as in minerescue and in long tunnels, and goingthrough passages too narrow for a big open-circuit air cylinder.

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PARTS OF BA

An open-circuit rescue or firefighter SCBAhas a fullface mask , regulator , aircylinder , cylinder pressure gauge , and aharness with adjustable shoulder straps and waist belt which lets it be worn on theback.

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Air cylinders are made of aluminium, steel, or of a compositeconstruction (usually carbon-fiber wrapped.) The composite cylindersare the lightest in weight and are therefore preferred by fire departments.

Air cylinders must be hydrostatically tested every 3 years forcomposite cylinders, and every 5 years for metal cylinders.

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HOW DOES IT WORK?

Open circuit SCBAs utilize either "positive pressure" or "negativepressure" operation.

1. NEGATIVE PRESSURE

A "negative pressure" SCBA may be used with a type of fullface maskwhich could be used as a gasmask (with a filter canister on thefacepiece's air inlet) or with an open-circuit breathing set connected tothe air inlet. Air is delivered to the wearer when he breathes in, or inother words, reduces the pressure in the mask to less than outsidepressure, hence the name "negative pressure". The limitations of thisare obvious, as any leaks in the device or the interface between themask and the face of the wearer (caused for example by small face skinwrinkles) would reduce the protection offered.

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2. POSITIVE PRESSURE:

"Positive pressure" SCBA addresses this limitation. By careful design,the device is set to maintain a small pressure inside the facepiece.

Although the pressure drops when the wearer breathes in, the devicealways maintains a higher pressure inside the mask than outside of themask. Thus, even if the mask leaks slightly, there is a flow of clean airout of the device, automatically preventing inward leakage under mostcircumstances. Although the performance of both types of SCBA may be

similar under optimum conditions, this "fail safe" behaviour makes a"Positive pressure" SCBA preferable for most applications.

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PREPARATION BEFORE USE

We perform two tests before use BA :Leak Test : Perform condensed check in order described below:

1. Open cylinder valve with approx. two turns of hand-wheel2. Read pressure gauge.3. Minimum pressure: 270 bar with 6L/300 bar cylinder.4. Close cylinder valve.5. The apparatus is tight if there is no noticeable drop of pressure

after 1 min.

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Check of Warning Device:

Open cylinder valve briefly and close again.

Slowly activate releasing button until air flows out, observingpressure gauge at the same time. The warning signal mustbegin to sound at approx. 55 bar.

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USAGE

From time to time during use check tightconnection between lung-governed demandvalve and facepiece. If the air supply isreduced to the activating pressure of warningdevice, a whistle sounds which continues tillthe air supply has been exhausted. When the

whistle starts to sound, the user must returnto fresh air.

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CHARGING CYLINDERS

Cylinders may only be charged with clean, dry air accordingto German Standart DIN 3188. After charged cylinders havecooled down to ambient temperature, than check thepressure to assume that maximum operating pressure is

maintained. If necessary, recharge the cylinders.There must be no humidity in the connecting thread.Completely empty (pressureless) cylinders must be dried.This is required to prevent excess moisture inside the

cylinder.

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One method of drying is to charge thecylinders twice fully (up to permissablepressure) with dry air from a compressor andafterwards releasing the air again. Atdischarging the valve must not freeze.

To prevent moisture in the cylinders,Cylinders should not be totally discharged.

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INSPECTION OF BA

MSC/Circular.850 - Guidelines for the Maintenance andInspection of Fire-Protection Systems and Appliances

Weekly testing and inspections :breathing apparatus cylinders do not present leakages.

Annual testing and inspections :breathing apparatus air recharging systems checked for air

quality

Five-year service :hydrostatic testing for all SCBAs cylinders

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SCBA IN 31.9 SECONDS