We evaluated nanofiber nonwovens with inherently flame-resistant properties for thermal, comfort, and particle-blocking performance when used in composites employed in firefighter personal protective equipment. The first objective of the evaluation was to understand whether a thin, lightweight nanofiber nonwoven would be more comfortable and also reduce heat stress, which is responsible for more than 60% of firefighter deaths and injuries. We evaluated the thickness, moisture management, and thermal properties of a nanofiber thermal liner in a turnout gear composite against the properties of a traditional nonwoven thermal liner. We found that use of a nanofiber nonwoven reduced the thickness of the thermal liner and its gear composite by 40% and 13%, respectively. The thickness reduction further enhanced thermal liner water absorption and shortened drying time. Additionally, the gear composites using the nanofiber nonwoven improved total heat loss by as high as 50 units (W/m², p = 0.002), while providing the same thermal protection performance (p = 0.161) when compared with the control gear composites. The second objective of this evaluation was to understand whether a nanofiber nonwoven could adequately block smoke particles that are carcinogenic to humans. A one-dimensional stretchable nanofiber nonwoven was embedded between two flame-resistant knits to create a hood composite. The study concluded that hood composite using the nanofiber nonwoven had improved filtration efficiency as high as 99%, or a fourfold improvement when testing particle sizes ranging from 0.1 to 0.8 µm. The filtration efficiency of the nanofiber hood composite remained intact after 50 laundries. Furthermore, we validated the smoke particle-blocking performance by the Fluorescent Aerosol Screen Test. When assessed by a wear trial for real-world applications, we found that the nanofiber hood was effectively protective from blocking smoke particles and also sufficiently sensitive to the situational awareness needed by firefighters.