Department radios and cell phones shall not be used within __ feet of unexploded devices.

The correct answer is 500 feet. This distance is prescribed as a safety standard when managing situations that involve unexploded devices, such as ordnance or munitions. The use of radios and cell phones within this proximity presents a risk due to the potential for electromagnetic interference. This interference can inadvertently trigger a detonation, putting personnel and the surrounding area in danger.

The 500-foot guideline has been established by safety protocols to ensure that responders maintain a safe distance from potentially unstable and hazardous materials. This distance allows for adequate precautionary measures to be taken, minimizing the risk of accidental activation of these devices. Adhering to this protocol is critical for the safety of first responders and can help prevent catastrophic outcomes in emergency service operations.