Overview - ISO 23121-1:2019 (Gas supply system)
ISO 23121-1:2019 specifies requirements for the gas supply system of inflatable buoyancy support systems used to prevent damaged ships from sinking or capsizing. The standard covers general requirements, installation and activation of gas-based inflation systems for buoyancy chambers installed in machinery spaces and cargo holds. It is intended to ensure safe, reliable inflation using gas media (including asphyxiants) while protecting habitable spaces and maintaining compatibility with fire‑fighting systems.
Key topics and technical requirements
- Scope and purpose
- Applies to gas supply systems that provide residual buoyancy for flooded or damaged ships.
- Permitted media
- Prohibits inlet media causing toxic concentrations in discharge spaces and forbids Halon 1211, 1301, 2402 and per‑fluorocarbons.
- Defines “asphyxiant” and requires safeguards when media can be harmful to health.
- System installation
- Components (cylinders, regulators, valves, hoses) must be securely fastened to withstand ship motions, shocks and vibrations.
- Cylinders must be installed in non‑habitable, separated spaces, mounted clear of bilge water and water‑accumulation surfaces.
- Pressure regulators (if used) shall comply with ISO 15738 to avoid sudden inflation damage.
- Activation and controls
- Buoyancy chambers must not activate automatically.
- Remote control valves require an indicator visible from the main helm (bridge or machinery control room).
- Systems must be operable between −15 °C and 65 °C.
- When gas media are harmful, a shut‑off valve distinct from the activation system must be fitted close to cylinders.
- Safety warnings and alarms
- Visual/sound alarms are required in protected spaces large enough to be occupied, activated before gas supply.
- Displayed information and warnings should use appropriate language and may use ISO 7010 symbols.
- Performance and sizing
- Quantity of cylinders determined by required buoyant force and chamber volume; cylinder fill must not exceed safe internal pressure at +65 °C.
Practical applications and users
- Who uses this standard:
- Ship designers and naval architects, shipyards, marine equipment manufacturers, classification societies, marine surveyors, ship operators and safety officers.
- Typical uses:
- Designing or retrofitting inflatable buoyancy support systems for damage‑control and flooding mitigation in machinery spaces or cargo holds.
- Specifying installation, controls, alarm integration and gas selection for compliance with safety and SOLAS considerations.
- Ensuring compatibility of buoyancy inflation with fixed fire‑extinguishing systems (see IMO SOLAS, Ch. II‑2A Reg. 4).
Related standards
- IMO SOLAS, Chapter II‑2A, Regulation 4 (fixed fire extinguishing systems)
- ISO 15738 - Gas inflation systems for inflatable life‑saving appliances
- ISO 7010 - Graphical safety symbols
Keywords: ISO 23121-1:2019, inflatable buoyancy support systems, gas supply system, marine safety, flooding mitigation, buoyancy chambers, ship design, IMO SOLAS.