In Episode 7, check out UL's Fire Safety Research Institute Advisory Board Member and Division Chief for Montgomery County (Maryland) Fire & Rescue Service, Charles Bailey, as he explains how heat transfers through turnout gear:

One of the most important lessons we as firefighters must understand is the use and limitations of our PPE. While we may not be able to outperform the thermal limitations of our turnouts, by applying the right tactics, we can certainly enhance our operational effectiveness and reduce the potential for thermal insult/injury.

Additional resources related to this consideration:

Article: Thermal response to firefighting activities in residential structure fires: the impact of job assignment and suppression tactic

Report: Fire Fighter Equipment Operational Environment - Evaluation of Thermal Conditions