Document Type
Article
Date of Original Version
2025
Abstract
Firefighters wear personal protective equipment (PPE) composed of multiple layers, each designed to serve a specific function in ensuring safety and comfort in high heat environments. The thermal liner is the innermost layer and plays a crucial role in thermal comfort by providing insulation and moisture management. Insulation provides protection from external hazards while moisture management keeps the wearer cool and dry.
Heat stress is a significant safety concern for firefighters, as prolonged exposure to high temperatures and insufficient evaporative cooling can lead to discomfort, injuries and or fatalities for them while on duty. Effective moisture management is critical in mitigating these risks, as moving sweat away from the body helps regulate body temperature, reduce discomfort/risk of injuries, and maintain performance. However, current firefighter PPE is heavy and multi-layered, often restricting water vapor permeability and limiting evaporative heat loss, which exacerbates heat stress.
The literature review examines current firefighter PPE systems, heat stress for firefighters and the physiological and material factors influencing thermal comfort. The meta-analysis then explores experimental research on the regenerated cellulosic fiber Viloft® (a specialty viscose rayon manufactured by Kelheim Fibres GmbH), a fiber primarily used and studied in underwear and sportswear context, but it also shows promise for use in thermal liners due to its unique combination of moisture wicking, absorption, and insulating properties that should be explored further. Viloft’s® cross-sectional shape and hairiness (by trapping tiny pockets of still air around the fabric, creating a natural thermal barrier that helps retain body heat) improve insulation and the hydroxyl group within chemical structure contribute not only to enhanced moisture absorption. The review concludes with recommendations for fiber blends that incorporate Viloft® to improve both comfort and protection in firefighter thermal liners.