What indicates that interior forces may be failing in their effort to quell the fire?

Encountering heavy smoke and heat serves as a significant indicator that interior forces may be struggling to control the fire. When firefighters are faced with an abundance of smoke coupled with high temperatures, it suggests that the fire is not being suppressed effectively. Heavy smoke indicates incomplete combustion and the potential for backdrafts or rapid fire spread, while high heat levels can compromise both the safety of the personnel on scene and the efficacy of firefighting efforts.

In contrast, consistent water flow signifies that firefighting operations are ongoing and effective. Visible improvements in visibility usually suggest that the conditions are improving, indicating successful suppression efforts, and low temperatures on the fire floor would imply that the fire is not reaching those areas, which is generally a sign of effective firefighting operations. Thus, heavy smoke and heat are critical signs of a deteriorating situation that require immediate assessment and response adjustments.