SCBA
Introduction about SCBA Full Form & Its Heroic Role Explained
A self-contained breathing apparatus, or SCBA, sometimes referred to as a compressed air breathing apparatus (CABA) or simply a breathing apparatus (BA), is a device worn by rescuers, firefighters, and others to provide breathable air in an immediately dangerous to life or health atmosphere.
The SCBA cylinder size comes in different sizes :
SCBA working principle
The SCBA works by providing clean, compressed air from the cylinder to the face mask via the pressure regulator. All except one of the SCBAs run on a positive pressure system, where the pressure within the mask is ever so slightly greater than the air pressure around it—keeping harmful contaminants out.
Airflow is demand-controlled; for example, air is sucked out during inhalation. While air in the cylinder falls to a critical level (usually 25%), a low-air alarm informs the user to leave the danger zone.
Parts of scba set
- Facepiece or mask: A full-face mask used for toxic gas, dust, and mists.
- Air cylinder: Contains compressed air (300 bar) and provides 30 to 60 minutes of breathable air.
- Pressure regulator: Reduce high cylinder pressure to a breathable level.
- Harness assembly: A wearable frame that holds the cylinder and supports the SCBA set.
- Alarm and gauge system: A low air alarm and pressure gauge for monitoring air level.
Types of SCBA
There are two types of SCBA available :
- Open-circuit SCBA : This type of SCBA is used in firefighting.
- Closed-circuit SCBA : This type of SCBA is used in mining and underwater operations.
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Application of SCBA
- Firefighting: smoke in building and toxic gas atmosphere areas.
- Industrial use : chemical plants, oil refineries, and confined spaces.
- Rescue operation: Building collapses and disaster zones with poor conditions.
- Hazardous material handling : gas leak, chemical spillage, and decontamination work.
- Mining and tunneling : protection from toxic gas and dust.
Safety features of SCBA
- The low-air alarm alerts the user to leave the area immediately.
- Emergency bypass valve Allow manual air release if the regulator fails.
- Face seal use to prevent air leakage
- Some SCBA models are digital inside the face mask and show a display.
Limitation of SCBA
Although life-saving in operation, SCBAs have a few limitations :
- Improper use is hazardous.
- SCBA air limit duration is 30-60 min.
- They usually weigh 10–15 kg and can be mobility-limiting.
- Most SCBAs limit of duration is 30–60 minutes of air.
- Incorrect use can be dangerous.
- Masks muffle speech, and signal training may be needed because of communication difficulties.
How to wear scba set
1. Pre-Wear Check
- Inspect cylinder pressure (cylinders with below 50 bar pressure are not in use).
- Inspect for damage or wear on the harness, facepiece, and hoses.
- Inspect regulator and bypass valve operation.
- Inspect that the low-air alarm is working.
2. Donning the Harness and Cylinder
- Hold the SCBA by the shoulder straps as a backpack.
- Slide arms through shoulder straps.
- Adjust and tighten the waist and shoulder straps so that the unit is near your back.
3. Don Facepiece Mask
- Hold the facepiece with one hand and place the other hand into the head harness. Pull the head harness over your head.
- Position the mask at the rear of your nose and mouth, in the center of your face.
- Tighten straps evenly—bottom, then middle, then top.
- Check for no leaks (perform a positive and negative pressure test).
4. Hook up the Regulator
- Connect the regulator to the facepiece port (normally clicks).
- Depending on the model, the airflow will automatically turn on, or you must press a button to have it come on.
- Breathe in to test that air is flowing freely.
5. Activate the Air Supply
- Fully open the cylinder valve by turning it to the left.
- Check your shoulder or chest pressure gauge to confirm airflow is present.
- Passive alarms or HUD readouts can be triggered on certain SCBAs—check status.
6. Low-Air Alarm Test
- Check or test that the low-air alarm system works.
- It will vibrate, ring, or flash depending on your SCBA configuration.
7. Pre-entry Final Safety Checks
- Ensure that all straps are properly fitted and tight.
- Test radio or communications equipment is working.
- Have someone test your equipment prior to entering risk areas.
SCBA cylinder capacity calculation
Example : 6-liters and 300 bar cylinder,
Total air = cylinder Capacity × Cylinder Pressure
Total air = 6 × 300
Total air = 1800 liters
The table below shows how much total air (liters) is available in the cylinder:
| No. | cylinder Pressure (Bar) | Capacity of cylinder (lit) | Total air (lit) |
|---|---|---|---|
| 1 | 300 | 6 | 1800 |
| 2 | 250 | 6 | 1500 |
| 3 | 200 | 6 | 1200 |
| 4 | 150 | 6 | 900 |
| 5 | 100 | 6 | 600 |
SCBA air consumption calculation
\[Time\; of \;duration=\frac {cylinder\;pressure\times\;cylinder\;capacity} {Average\;consumption}\;\;\]
A man take a breath in 1 minute = 16 times
Every breath inhale air = 2.5 liters
= 16 × 2.5
= 40 lit
If we have a 6-liter SCBA cylinder with 250 bar pressure on the pressure gauge, how do we calculate the duration of time in minutes ?
\[Time\; of \;duration=\frac {cylinder\;pressure\times\;cylinder\;capacity} {Average\;consumption}\;\;\]
\[Time\; of \;duration=\frac{250\times\; 6}{40}\;\;\]
= 37.5 minutes
Working duration = total duration – safety factor
Working duration = 37.5 – 10
Working duration = 27.5 minutes
The table below shows actual working minutes without a safety factor:
| No. | Cylinder pressure (bar) | Duration (minutes) | Working duration without safety factor |
|---|---|---|---|
| 1 | 300 | 45 | 45-10=35 |
| 2 | 250 | 37.5 | 37.5-10=27.5 |
| 3 | 200 | 30 | 30-10=20 |
| 4 | 150 | 22.5 | 22.5-10=12.5 |
| 5 | 100 | 15 | 15-10=05 |
Q&A
- What is a SCBA set?
Ans. A self-contained breathing apparatus, or SCBA, sometimes referred to as a compressed air breathing apparatus (CABA) or simply a breathing apparatus (BA), is a device worn by rescuers, firefighters, and others to provide breathable air in an immediately dangerous to life or health atmosphere.
2. What is the purpose of the SCBA set?
Ans. The main purpose of SCBA is to protect users against oxygen deficiency, dust, toxic and harmful gases, and vapors.
3. What is 40 in the SCBA formula?
Ans. \[Time\; of \;duration=\frac {cylinder\;pressure\times\;cylinder\;capacity} {Average\;consumption}\;\;\]
4. What are the 2 main types of SCBA?
Ans. There are two types of SCBA available :
Open-circuit SCBA : This type of SCBA is used in firefighting.
Closed-circuit SCBA : This type of SCBA is used in mining and underwater operations.
5. How many liters is a SCBA?
Ans. SCBA cylinders are available in five sizes—1 L, 2L, 4L, 6L, 6.8L, 8L and 9L to cater to all self-contained breathing apparatus and emergency escape breathing devices.
