The short answer
An acetylene cylinder is filled solid with a porous mass and charged with acetone or DMF. Acetylene gas is then dissolved into that solvent. Because free acetylene can decompose under pressure, storing it dissolved — subdivided through millions of tiny pores — is what makes it safe to keep at a useful pressure.
What is inside an acetylene cylinder
| Component | What it does |
|---|---|
| Porous mass | A monolithic solid (e.g. calcium silicate) filling the whole shell; its fine pores stop decomposition spreading and hold the solvent. |
| Solvent | Acetone or DMF, absorbed into the porous mass; acetylene dissolves into it in proportion to pressure. |
| Acetylene | The gas itself, dissolved in the solvent — the cylinder holds far more this way than by compression alone. |
| Valve & fusible plug | Cylinder valve for controlled withdrawal, plus fusible safety devices that release if the cylinder overheats. |
Safe filling and withdrawal
Because the gas must dissolve evenly, acetylene cylinders are filled slowly and under cooling — never rushed. The same logic applies in reverse when you use one:
- ✓Draw gas at a moderate rate — pulling it too fast carries solvent out with the acetylene and can chill the regulator.
- ✓A single cylinder has a limited continuous draw-off rate; use a manifold or cylinder bank for higher demand.
- ✓Always fit an approved flashback arrestor between the regulator and hose.
Storing acetylene cylinders correctly
- ✓Store and use upright, valve up, secured against falling.
- ✓Keep in a well-ventilated area away from oxygen cylinders, heat and ignition sources.
- ✓If a cylinder has been horizontal, stand it upright for a settling period before use so the solvent returns to the porous mass.
- ✓Never expose to temperatures that could soften the charge or trip the fusible plugs.