Purpose of the study: The purpose of this study is to examine the effectiveness of several types of personal respiratory protection equipment at styrene exposed laminators under real work place conditions. Subjects and method: 99 male styrene exposed workers were examined. During their lamination activities the average styrene concentrations in air ranged between 30 to 60 ppm (maximum: 205 ppm). The laminators were followed during an usual workweek from Monday to Thursday. The external styrene exposure was measured by means of passive active carbon badges. The excretion of mandelic acid (MA) and phenyl glyoxylic acid (PGA) in end-of-shift urine samples was used to quantify the internal styrene load. During the work shift some laminators did not use respiratory protection masks. The majority used either a half face mask with active carbon filter or an air purifying respirator. Results: The respiratory masks were worn during an average between 31% and 72% of the work time. The styrene concentrations of the ambient air were -depending on the activity- in the range of 30 to 60 ppm. The end-of-shift concentrations of MA and PGA in urine samples varied considerably, their means range from 153 to 606 mg/g creatinine. The comparison shows that workers with air purifying respirators experience the lowest internal styrene body burden in spite of high external exposures. Their effectiveness during usual working condition was around 83% whereas the use of half face masks with active carbon filters reduce styrene exposure only of 26% as an average. Conclusions: The use of styrene-containing resins in boatbuilding can be associated with increased external styrene exposure of the laminators. During the use of different types of respiratory protection masks it is shown that only the application of air purifying respirators leads to a significant reduction of the internal styrene body burden of 83% when worn during 72% of the total work time. In this way it is possible to comply with or to stay clearly below the biological limit value of 600 mg MA + PGA/g creatinine (BAT-value).