The time spent on-call for a worker, in this case a volunteer firefighter, at their home, with the obligation to physically remain there, be available to their employer and respond to a call as soon as possible, should be considered as "working time" in the sense of the directive on working time arrangements (2003/88/EC).
These obligations significantly reduce the worker's possibility to exercise another activity and is different to that of another worker who, whilst on standby, simply has...