Nothing showing generally requires what by the first arriving unit?

• A. Immediate suppression
• B. Ventilation
• C. An investigation
• D. Rescue operations

Answer: (C)

When nothing is showing, the first arriving unit must perform a rapid investigation as part of size-up to determine if a fire exists inside, where it is, and how large it might be. Fires can burn hidden behind walls or in concealed spaces, so exterior signs may be absent even though there is a fire. By quickly confirming fire presence and location, responders can decide on the appropriate course—interior suppression, resources to call for, or a defensive plan—while avoiding premature actions like ventilation or rescue that aren’t yet warranted by the actual conditions. The investigation is the key step that guides the rest of the incident actions.