Are you over reacting? Who knows? If you have a risk specified within the Confined Spaces Regs and it is reasonably foreseeable that someone may get harmed or killed - then you need to complete a confined space risk assessment. You can then decide if the risk is significant and what you might have to do to remove or (more likely) manage the risk. A Permit to Work may be one of the risk controls you might want to intoduce.

In terms of the normal circumstances ie when the flooding is not deployed then, under the Confined Space regs, INHO this is not a confined space. However, if the flooding device deploys, it probable would be. Regardless what is needed is a SSOW with a secure isolation to prevent the deployment of the device. The PTW is a good idea but only in support of a secure isolation system - remember everyone, A PTW DOES NOT MAKE THE JOB SAFE. It is a bit of paper!

In my view switched off is not enough, should be securely locked off.

Martyn You don't say what type of gas is used as a fire suppressant? So let's assume it is harmful to human beings and therefore controls need to be in place for workers entering the server. These controls could include a PTW system. Whether a formal PTW system is employed will depend on a number of factors - for example, the remoteness of the locations, supervision, training, lock off, etc...these are the factors which will determine the need for a PTW system. A PTW system per se will not necessarily reduce the risk - it is the robustness of the system which is the overriding factor.