[Symbiote]

I think it's a bit more complicated, since the extinguishing system is intended to be used in emergencies.

The usual system, e.g. in a train maintenance depot:

- Employee is going to work underneath the train, which therefore must not be moved. He isolates the power supply, and locks this isolation with his padlock.

A situation in which it's suddenly very important to reconnect the power is extremely unlikely. If the employee forgets to remove his padlock, it's disruptive but not dangerous. (I've seen this system once, and when people left for the day they were supposed to lock their padlocks on a special board as part of clocking out.)

For the datacentre, if the fire alarm goes off, everyone is supposed to leave by the nearest exit -- not go back the way they came in, unlocking their padlocks to allow the extinguishing system to be used.