What is a sign that a Type B fire is completely controlled?

The absence of smoke and heat is a clear sign that a Type B fire is completely controlled. When a Type B fire, which involves flammable liquids and gases, is extinguished, it should no longer produce combustion, which means that the flames are out and the reactive materials have been neutralized. Smoke is a byproduct of burning material, so its absence indicates that the fire is not ongoing. Additionally, a lack of heat suggests that the fire source has been effectively cooled to a safe temperature, reducing the risk of re-ignition.

While other options may indicate aspects of fire control, they do not directly confirm that the fire has been fully extinguished. A visual inspection can show the state of the area, but could still miss smoldering embers or hot spots. Returning to regular activities may not be safe until there's concrete evidence of fire control. Finally, relying solely on the absence of the need for other extinguishers may not be a comprehensive measure of fire safety. Therefore, the absence of smoke and heat remains the most definitive sign that a Type B fire has been completely controlled.