The dual effects of the air gap on thermal aging and thermal protection of firefighting suits exposed to wildland fires

In wildland firefighting, the air gap (AG) between clothing and the human body can effectively decrease heat transferred to skin but has a negative impact on thermal aging of clothing. Heat transfer to skin from a fire source can led to burn injuries and heat is transmitted between adjacent AGs parallel to the skin surface. An open AG simulator was developed to explore the dual effects of the AG on fabric thermal aging and skin thermal protection. Results indicated that thermal aging of fabrics was affected by the size and boundary form of the AG. Open and closed AGs increased second-degree burn times by 37.2–232.9 and 32.4–160.3%, respectively. The 12-mm and 18-mm open AGs decreased thermal aging of the fabric while maintaining good thermal protection compared to other AG conditions. The findings indicate that an appropriate AG design can balance thermal aging and thermal protection of firefighter suits.