SCBA Set | Safety blog

SCBA – self contained breathing apparatus

Synonym : BA Set, 

SCUBA - Self-contained ‘underwater’ breathing apparatus
[This set is used to breathe under water]

In this blog we will learn

1. Self contained breathing apparatus parts 
2. Types of SCBA 
3.Self contained breathing apparatus details 
4.Uses of Self- Contained Breathing Apparatus 
5.Self contained breathing apparatus specifications 
6.Cylinder carrying Practice 
7.Check points of breathing apparatus 
8.Supplier details - self contained breathing apparatus manufacturers
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Oxygen Deficient Atmospheres - OSHA

If oxygen deficiency takes place following consequences are happen

19.5% - Minimum acceptable oxygen level.

15-19% - Decreased ability to work.

12-14% - Respiration increases. 

10-12%  - Respiration increases more and lips will become blue

8-10% - Mental failure, Unconsciousness

6-8% - 8 minutes-fatal, 6 minutes -50% fatal

4-6% - Coma in 40 seconds. Death

1. Self Contained Breathing Apparatus Parts

SCBA Set consists of following main parts 
  •        High pressure cylinder - Pressure gauge, Air regulator
  •             Inhalation connection – Face shield, hose, Pressure regulator
  •        Back plate – Waist belt, Shoulder strip, Remote pressure gauge, Bypass valve, PASS Alarm [Personal alert safety system alarm]
SCBA Set | Safety blog

Material of construction of SCBA Set

Air cylinder is most important and critical part of BA Set.
Cylinder is made with

·         Steel
·         Aluminum
·         Carbon fiber Composite material [ Lighter in weight]

This container is wrapped in Glass fiber or carbon fiber.

Hydro testing of cylinders

MOC Hydrotest Duration
Steel              5 Year
Aluminium  5 year
Carbon fiber composite material 3 Years

Used Breathing apparatus are filled with cascade storage system or air compressor.

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2. Types of SCBA

There are two types of SCBA

1.       Closed circuit SCBA – Longer duration supply of breathing apparatus, used in needed in mines and tunnels rescue

In close circuit exhaled air is recycled by using an granular solid adsorbent scrubber to remove the carbon dioxide and replenish the consumed oxygen with oxygen from a solid, liquid, or gaseous source.

2.       Open circuit SCBA – This filled with filtered compress air rather than oxygen.

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3. Self-Contained Breathing Apparatus details

SCBA Set containing High pressure cylinder with inhalation connection with back plate accessories.

`Pressure regulation:

It has two pressure regulation systems in 
  • 1st Regulator it gives reduced pressure in range 4 – 8 atmospheric pressure.
  •  Second stage regulation is a demand valve which gives output pressure just above atmospheric pressure which gives air when person breathing or continuous positive pressure.
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There are two types of Pressure system in face shield

  • Negative pressure system: This found in older equipment's and almost not used. When internal pressure of mask dropping below ambient pressure then it activate flow. In case of inaccurate face sealing it sucks outer air inside mask which has potentiality to cause accident.

  • Positive suction system: This pressure inside face shield is slight high pressure then ambient outside pressure. Supply of air activated when pressure drop is created [Pressure drop is still above atmospheric pressure]. This system prevents outer gas inhalation.
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SCBA Service time

SCBA Set cylinder decides its Capacity. It’s come with standard sizes 4 Liters, 6 Liters, 6.8 Liters. 

It is also available in time duration on with 60 minutes, 45 minutes, 30 minutes and 15 minutes [ 15 minutes bottle is for only escape use]

SCBA Set service time can be calculated by following equation

Average human air consumption = 40 Liters / minutes

           There are 2 another factors which can reduce service time of breathing apparatus 25 – 50 %

1. Physical fitness and lung capacity of the person who is wearing it.

2. Type of work varies breathing speed of person.
  • When pressure drops below 55±5 atmospheric pressure it gives audio visual alarm on PASS system
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4. Uses of Self- Contained Breathing Apparatus

Self- Contained Breathing Apparatus is used in
  • Polluted environment with Chemical, Biologically, Radiology or Nuclear.
  • Oxygen deficiency areas – Confined space, Toxic dusted area.
In cure of Ebola SCBA sets are used to prevent infection.

5.  Self contained breathing apparatus specifications

Breathing apparatus has some specification which monitored by Regulatory bodies following –
1. NFPA USA - National Fire Protection Agency
2. NIOSH  - National Institute for Occupational safety & Health
3. Europe 89/686/EEC4. European Standards EN 137: 20065. ANSI - American National Standard Institute6. MSA – Measurement safety analysis
7. WAC – Washington Administrative Code
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General Specification

1. SCBA must tested on temperature range -30°C to +60°C
2. SCBA has 1200 liter filtered air
3. SCBA shall be capable of providing minimum 30 minutes of service time
4. SCBA has audio visual alarm which can be operated when pressure drops below 55±5 Atmospheric pressure. Audible alarm can be operated pneumatic air pressure or by electrically battery operated
5.  Maximum Cylinder service life is 20 years from manufacturing and advisable years are 15 years.
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6. Cylinder carrying Practice

Cylinder is not handled with hand cover with Pressure Gauge or Air regulator. It sold be carried by neck of cylinder.

7. Check points of breathing apparatus

Daily checkpoints

1. Check physical condition of rubber gauge protector on air cylinder is properly positioned or not.
2. Check that the cylinder pressure is sufficient or not
3. Open the cylinder air regulator to check hose leakage or not
4. Check Alarm system is working or not by closing main air regulator.
5. Close the air cylinder gauge & push the second stage regulator demand valve
6. Check bypass valve working or not.

Weekly check

1. Gauges are checked after use or weekly. Check Air cylinder pressure and remote pressure gauge reading is same or any deviation
2.  Physical condition of container

After use Inspection

1. Exhalation valve must cleaned properly after use
2. Check speaking diaphragm & Ensure microphone is in center.

Cleaning and sanitizing procedure

1. After each use of SCBA cleaning & sanitizing carried out.
2. Remove electrical equipments outside like Voice amplifier, heads up display, Battery etc.
3. Clean face shield accessories with wet water cloth. Don’t use alcohol or any cleaning solvent because it harms rubber
4. Rinse mask through water [<120°C]
5.  Let accessories dry. Don’t use compressed air to dry.

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8.  Supplier details - self contained breathing apparatus manufacturers

1. For various models check official 3M Scott –
2. Various parts & combined SCBA –
Referral details

Read more about "Industrial Policies" from Industrial Guide - Click here

Important links
Wikipedia - Read now
Read on STS Japan - Read now
Read on Dreager - Read now

Photo credits

Thanks for reading - SCBA Set | Safety blog
Naitik Patel
Industrial Guide

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