Objectives: This study aims to assess the concentrations of ammonia and hydrogen sulfide according to task unit area at swine farms. Methods: A total of six swine farms were selected for this study. Ammonia and hydrogen sulfide were monitored using a real-time multi-gas monitor which could sample the gases simultaneously. The sampling was done in the pig building, manure storage facility and composting facility of each farm. Results: The concentration of ammonia in the pig buildings(GM 22.6 ppm, GSD 2.3) was significantly higher(p<0.0001) than in the manure storage facilities(GM 10.4 ppm, GSD 2.7) and composting facilities(GM 8.6 ppm, GSD 2.8). The concentration of hydrogen sulfide in the manure storage facilities(GM 9.8 ppm, GSD 3.2) was higher(p<0.0001) than in the pig buildings(GM 2.3 ppm, GSD 2.3) and composting facilities(GM 1.9 ppm, GSD 2.5). In particular, the levels of hydrogen sulfide in the confined manure storage facilities were higher than those in open-type facilities and the peak concentration(98 ppm) in the confined facilities was approximate to 100 ppm, at the value of Immediately Dangerous to Life or Health(IDLH). Conclusions: Suffocation accidents caused by hazardous gases at a swine farm have occurred annually. Real-time monitoring of the hazards should be done in order to protect farm workers and livestock from the sudden accidents.