The aim of this study was to determine firefighter’s exposure to benzene and toluene during a fire drill by monitoring air benzene and toluene, and their corresponding urinary metabolites. A liquid chromatography mass spectrometry (LC–MS) method with a minimal of sample preparation steps was developed for the benzene metabolite s-phenylmercapturic acid (SPMA) and the toluene metabolite s-benzylmercapturic acid (SBMA) in urine. Urine samples and air samples were collected from nine firefighters during and after a fire drill in a non-environmentally refurbished house. Benzene and toluene were detected in the air samples with a median concentration of 15.5 ppm and 3.2 ppm, respectively. The metabolites SPMA and SBMA was also detected in all urine samples donated ≥ three hours after the fire drill with a median concentration of 0.6 μg/g creatinine and 5.9 μg/g creatinine, respectively. By our knowledge, this is the first study detecting SPMA in urine from firefighters.