Purpose – The purpose of this paper is to investigate the incremental impact of firefighter’s personal protective equipment (PPE) on lower body range of motion (ROM) while walking to suggest areas of design improvement for enhanced mobility and safety. Design/methodology/approach – Eight male and four female firefighters participated in the study. Lower body ROM was assessed while they walked in four different configurations of PPE, including turnout ensemble, a self-contained breathing apparatus (SCBA) and boots. The impact of each added PPE item, and gender differences were statistically analyzed. Findings – Wearing firefighter turnout ensemble and SCBA reduced ROM in the lower body in the sagittal and transverse planes. A significant reduction in ROM for anterior-posterior movement at the ankle and the ball of the foot was found while wearing rubber boots with turnout ensemble and SCBA. This puts firefighters at higher risk of experiencing foot injuries and physical strains. A significant increase in medial-lateral movement of the foot while wearing rubber boots may increase risk of ankle sprains. A greater reduction in ROM at the ankle and the ball of the foot for female firefighters may imply greater risk for women compared to men, while wearing boots. Practical implications – Reducing the inflexibility and bulkiness of boots is critical to improve firefighter’s lower body mobility and safety. Originality/value – This study implemented 3-D motion capture technology to analyze how wearing firefighting gear impacted lower body motion. It provides quantitative evidence to recommend ergonomic boot re-design.