The first step in the risk assessment which you must carry out is to identify the hazards. They may not be obvious and need to be considered by a competent person with suitable and sufficient knowledge of the confined space in question, including a recent history of its usage, contents and condition.
A separate risk assessment is required before each occasion that work in a confined space is completed — even if work has been completed in that area before. This is because the risks are transient and will depend upon the type of work being done as well as the environment in the confined space – which can sometimes change very quickly.
The risk assessment should consider at least the following, where applicable:
- previous contents of the confined space;
- residues from previous contents or processes;
- resultant products from likely chemical reactions in the confined space;
- the effects of contamination and/or corrosion;
- possible causes of oxygen depletion or enrichment;
- the physical dimensions and the effect this may have on rescue plans;
- the use of cleaning materials or other preparatory activities;
- all possible sources of ignition, including sparks from steel-on-steel impacts;
- ingress of substances from adjoining processes or services;
- the tasks to be performed;
- the working materials and tools to be used;
- the suitability of those who will be completing the tasks, including contractors;
- the need for any training or refresher activities prior to the work being started;
- the communication arrangements and any hazards they may pose; and
- the emergency rescue arrangements.
A safe system of work should also be set down in writing. Where the risk assessment identifies significant levels of risk, then a permit-to-work may need to be prepared (see Managing Entry) for the task, fully agreed by all concerned and, where possible, tried out before the work starts in earnest.
The risk assessement pro-forma may also help you to write the safe system of work and complete the risk assessment.