We installed an effective, practical and low-cost smoking corner in an office to protect against passive smoking. The smoking corner was separated from the non-smoking area with transparent, nonflammable screens. Four exhaust fans were installed in the smoking corner so that there was no leakage of environmental tobacco smoke. The required exhaust air rate in the smoking corner was pre-calculated from the volume of the smoking corner and the rate of consumption of cigarettes. The suspended airborne particle concentration definitely decreased in the non-smoking area after installation of the smoking corner. The result of a questionnaire survey also revealed the improvement in the air quality in this office.