(1) With respect to hazardous factors prescribed by Presidential Decree which are likely to cause a serious health impairment of employees, such as carcinogenic substances, each business owner shall maintain the exposure concentrations of such hazardous factors in the workplace at or below the permissible level prescribed by Decree of the Ministry of Employment and Labor; provided, this shall not apply in any of the following cases:
1. Where installing or improving facilities and equipment that handle, or purify and discharge, hazardous factors is impossible with currently available technology;
2. Where a serious defect occurs in facilities and equipment due to a natural disaster, etc.;
3. In cases of temporary works and short-term works prescribed by Decree of the Ministry of Employment and Labor;
4. In other cases prescribed by Presidential Decree.
(2) Notwithstanding the proviso, with the exception of the subparagraphs, of paragraph (1), a business owner shall endeavor to maintain the exposure concentrations of hazardous factors at or below the permissible level referred to in paragraph (1).