Siting a Cylinder - Hierarchy of Control
The size and number of gas cylinders in use or storage should be kept as small as practicable, having regard to the task(s) being performed and the need to maintain supply.
The hierarchy of storage options for any gas cylinders is:
- Use a gas generator (where reasonably practicable)
- Locate in a safe place (suitable gas cylinder store) in the open air
- In specially designed, dedicated and well-ventilated gas cylinder storage/manifold rooms eg with two opposing walls that are 50% open to air
- Inside buildings in suitable gas cylinder cabinets.
The best approach is to dispense with gas cylinders altogether and use gas generators. These are commonly and successfully used to produce hydrogen for gas chromatography and nitrogen for mass spectrometry. Acetylene generators are also available.
Where none of the above is reasonably practicable, the gas cylinder should be secured in a safe place close to the point of use and removed to storage in one of the above locations as soon as possible after use.
It may not be possible or desirable for storage of cylinders of medical gases or breathing air to be stored in the open air but nevertheless the aim should be to minimise the number and size of cylinders stored within buildings, allowing adequate ventilation and protection from fire or other damage.
Collation of Information for the purposes of risk assessment
The above hierarchy should be considered as part of the risk assessment process. The responsibility for looking at overall risks connected with gas cylinders will rest with the space owner and Facility Manager (where relevant). Like all risk assessment practices, it is the responsibilty of the space owner to demonstrate why the first option in the hierarchy of control was not chosen. In this example, the first question should always be, can you use a gas generator?, thus removing the need for a cylinder altogether. If this is not reasonably practicable, then can the cylinder be located outside in a suitable gas store?, essentially moving down the hierarchy each time. The risk assessment must be written down justifying the choice made and clearly detailing any risks that remain present and how these will be minimised to an acceptable level.
Gas cylinders inside a building are not ideal, due to the obvious risks they pose in relation to fire and potentially oxygen depletion, so the hierarchy of control should always be worked through before this option is chosen.