We plan to work totally flexibly at one office - ie staff can use any desk on ANY FLOOR. This gives us the practical headache of how we can ensure consistent fire marshal cover on every or any floor as we can't determine who will sit where and when. Has anyone come across this situation before and found a solution please? We don't have any permanently on a set floor....

We are moving to a flexible working environment like you describe. We have fire wardens who on hearing the alarm make sure that the floor that they are on is cleared, and then they get themselves out. No roll call etc. They report back to the Incident Control Officer that such and such a block is clear and that information is passed on the fire brigade. Our site is divided into blocks and we have a phased evacuation (block by block) so this means that there is always enough spare wardens to check any block that is being evacuated. In theory a situation could arise where there were no wardens in a block but in reality this is unlikely.