What restriction does not apply to working on personal projects during on-duty time in fire stations?

The correct choice indicates that personal projects during on-duty time can use department supplies, which is not a restriction. This understanding is important as it highlights that department supplies may be available for personal projects, assuming they are permitted within the fire station's policies.

In a fire station setting, using departmental resources responsibly is essential, and there may be guidelines that allow for the use of such supplies under certain conditions. This could foster a positive work environment where crew members can engage in personal projects that contribute to their well-being or hobbies while still adhering to professional standards.

The other choices imply restrictions that are generally part of departmental policy—like the need to report projects to a supervisor, ensuring that projects are bounded in time, and involving only personal items. Each of these maintains accountability and professionalism during on-duty hours.