If you are shopping for a carbon fiber SCBA cylinder, you will quickly run into the terms “Type 3” and “Type 4.” These labels describe how the pressure vessel is constructed — in particular the liner material and the way the carbon fiber composite carries the load. Here is what each type means, how Type 3 and Type 4 compare on weight and corrosion resistance, and which buyers each one suits best.
What the cylinder “types” actually mean
Composite pressure vessels are commonly classified into four types:
- Type 1 — all-metal construction (steel or aluminum) with no composite wrap. Simple and robust, but the heaviest option.
- Type 2 — a metal liner with a partial composite wrap, usually hoop-wound fiber around the cylindrical section. Lighter than Type 1.
- Type 3 — a metal liner, commonly aluminum, fully wrapped in a composite such as carbon fiber. The liner and the wrap share the structural load. Type 3 is a long-established choice for SCBA and breathing apparatus.
- Type 4 — a polymer (plastic) liner, often PET, fully wrapped in carbon fiber composite. The liner mainly serves as a gas barrier while the composite carries the load.
Type 3 vs Type 4: aluminum liner vs PET plastic liner
The core difference is the liner. A Type 3 cylinder relies on an aluminum liner that contributes to the vessel’s strength, while a Type 4 cylinder uses a lightweight PET plastic liner that does not share the structural load. Because plastic is lighter than aluminum and cannot corrode, Type 4 cylinders are typically the lightest of the four types and are highly resistant to internal corrosion — a real advantage in humid, coastal, or marine firefighting environments. Type 3 cylinders counter with a long service history in fire services and industrial breathing apparatus worldwide.
Weight and corrosion compared
For the same water capacity and pressure rating — for example a 6.8L, 300 bar SCBA cylinder — a Type 4 tank generally weighs less than an equivalent Type 3 tank, because the PET liner weighs less than an aluminum liner. On corrosion: a metal liner can corrode if moisture gets inside the cylinder, while a plastic liner is inherently corrosion-free. For teams that work around water, humidity, or chemicals, that difference matters over years of service.
Which type fits which buyer?
Firefighting SCBA teams. Both Type 3 and Type 4 cylinders are used in self-contained breathing apparatus. If your priority is cutting carried weight for firefighters and maximizing corrosion resistance, a Type 4 cylinder is the natural pick — for example, our 6.8L Type 4 SCBA cylinder for firefighting and rescue.
Industrial safety and confined-space rescue. Refineries, chemical plants, and rescue teams face corrosive atmospheres and long standby periods. A PET-liner Type 4 cylinder avoids liner corrosion during storage and is easier to carry and handle — see the 6.8L Type 4 SCBA cylinder with a PET plastic liner. You can also browse the full Type 4 cylinders range.
What to check before you buy
- Pressure rating and capacity. Match the cylinder to your SCBA set — 300 bar / 6.8L is a common SCBA configuration.
- Certification. Confirm the cylinder carries the standard your region requires, such as EN 12245 or the relevant DOT/TC marking, and check that it is within its service life and inspection interval.
- Service life and retesting. Composite cylinders have a defined service life and periodic inspection requirements that vary by standard and jurisdiction — verify before purchase.
- Valve compatibility. Check the valve thread and outlet against your breathing apparatus or filling station.
- Construction type. Decide between Type 3 (aluminum liner) and Type 4 (PET liner) based on weight, environment, and budget.
Bottom line: Type 3 and Type 4 carbon fiber cylinders both serve SCBA and industrial safety well. Choose Type 4 when minimum weight and corrosion resistance matter most; choose Type 3 for its long-established track record. Either way, buy a certified cylinder that matches your apparatus and local regulations.