What is simultaneous evacuation?
Simultaneous evacuation is a strategy in which everyone in a building leaves at the same time on the alarm. It is the default in workplaces and is sometimes adopted temporarily in residential blocks.
It is the simplest strategy to understand and the most demanding on the building. Every stair has to carry everyone, and the alarm has to reach everyone at once, which is why it is not automatically available in a block designed around stay put.
Where it is introduced into a residential building as an interim measure, it usually requires a common alarm system that the building did not previously have, and often a waking watch until that is installed.
The change has to be communicated to every resident, because a building where half the occupants believe one strategy applies and half believe another is worse than either strategy consistently applied.
In practice
A block moved to simultaneous evacuation with no common alarm.
The strategy requires everybody to leave at once and there is no means of telling them to.
Changing the strategy changes what the building has to provide, and the detection and warning provision is usually the expensive part.
A waking watch is a temporary bridge to that, not a substitute for it.
What goes wrong in practice
- Adopted without the alarm coverage needed to make it work.
- Announced by letter only, leaving residents who did not read it on the old strategy.
- Kept in place indefinitely as an interim measure while the underlying defect is not progressed.