What did the firefighters use to determine the visibility and heat conditions of the structure during their operation?

The firefighters relied on physical sensations as they entered the structure to gauge visibility and heat conditions. This approach utilizes the immediate feedback that firefighters receive through their bodies, helping them to quickly assess the situation. By feeling the heat on their skin and observing changes in temperature, they can make swift decisions about the level of danger present and whether to advance further into the environment.

While personal experience and training, along with feedback from incident command, contribute to overall situational awareness, the immediate physical sensations offer direct and real-time data that is crucial during operations. Firefighters are trained to recognize these sensations, which are essential for making quick decisions about safety and tactics in fire situations.

Thermal imaging cameras, while effective tools in many scenarios for assessing conditions, may not always be used or available in every situation, making the reliance on personal sensory feedback vital in such circumstances.