The duration of usage for breathing apparatus is between 10 minutes (short-term
SCBA) up to about 60 minutes (long-term SCBA). Depending on requirements, you
can use cylinder volume, pressure and thus the amount of compressed air specific
to your application. In addition, duration of usage depends on your personal air
consumption.
FOR EXAMPLE:
- Compressed air cylinder: Volume: 6.8L
- Pressure: 300 bar
- Volume of air: approximately 2040L
- Average air consumption: approximately 40 L/min
- Usage time: approximately 51 min
In fact, there are two aspects to consider:
1. Air Supply Duration
- A 6.8 L / 300 bar SCBA is rated for 51 minutes, but real working time is often 20–35 minutes, depending on activity and stress.
- A 9 L / 300 bar SCBA is rated for 67 minutes, but actual time is usually 30–50 minutes.
- Escape sets (small cylinders like 3L/300 bar) last only 10–15 minutes.
So, in a single entry, a firefighter is typically inside for 20–35 minutes before air runs low.
2. Continuous Wear Time (Safety & Health Limits)
Even if you refill or switch cylinders, SCBA isn’t designed for hours of continuous wear:
- Weight & heat stress: SCBA sets weigh 10–15 kg; long use leads to fatigue and dehydration.
- NFPA & EN practice: Firefighters are usually rotated after one cylinder (20–40 min inside), followed by a rehab period (rest, hydration, medical check).
- Maximum safe stretch: Generally one cylinder use at a time; rarely more than 1 hour continuously with proper rotation.
There is also another case that we need to note, when we finished the refilling of a cylinder, the pressure maybe down to 280 bar after a few minutes. What’s the problem? Because when we refilling the first time, the data maybe up to 300bar due to the higher temperature. However, the data maybe down after cooling. So, most fire brigades use the HP cylinders storage systems.
If you have any comments, please feel free to contact us.
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