Cooling phase – Cool with water spray for one hour, using ground monitors and/or lashed jets; any firefighters carrying out essential tasks within the hazard area must have appropriate personal protective equipment (PPE) and make full use of all available substantial cover/shielding
Stop water cooling after one hour and check to see if the cylinder shell has been cooled to ambient temperature; the ‘wetting test’ and/or thermal imaging equipment should be used.
The ‘wetting test’:
- Get a clear view of the cylinders from a shielded location
- Briefly spray water on to the cylinder surface
- Stop spraying and looking for signs of steam rising from the surface of the cylinder
- If steam is not seen, check to see whether the wetted cylinder surface dries out quickly
- If either check is ‘failed’ (if steam is seen or the cylinder surface dries out quickly) then water cooling must be re-applied for one hour before testing again
- If both tests are ‘passed’ (if there is no steam and the cylinder surface does not dry out quickly) then the ’monitoring phase’ should start.
- Do not move the cylinder and maintain a risk assessed hazard zone
Monitoring phase – The cylinder should still not be moved for a further one hour and an appropriate, risk assessed hazard zone should be maintained. This monitoring phase is required due to the possibility of internal decomposition. During the monitoring phase, check the temperature of the cylinder at least every 15 minutes – if any increase in temperature is observed continuous water cooling should be applied for a further hour before the temperature is rechecked
When the cylinder remains effectively cooled for the whole of the ‘monitoring phase’ (i.e. the shell temperature remains at ambient temperature for one hour without being water cooled) and is not leaking, there is no risk of cylinder failure and it should be handed over to the responsible person or agency on-site.
Treat leaking acetylene cylinders with greater caution as they have a higher risk of decomposition occurring.
Multiple cylinders (or substantially concealed single cylinders) present a higher level of risk because the cooling water may not come into contact with a substantial proportion of the cylinder shell, therefore limiting the effect of cooling – if significant areas of the cylinder(s) are thought to be ‘dry’ then the cooling phase should be extended.
Refer to Control measures – Cordon control: Cylinders and pressurised gas and Cool pressurised gas containers.
Figure: Gas cylinder cooling procedure