As used herein, the permissible exposure limit refers to the following:1. The 8-hour time-weighted average: The 8-hour time-weighted average for substances not designated as “Ceiling” in Attachment 1 refer to levels to which workers may be repeatedly exposed during a standard eight-hour workday without adverse health effects.2. The short-term exposure limit: For any substance without designation of "Ceiling" in Attachment 1 and any substance listed in Attachment 2, the short-term exposure limit shall be calculated by multiplying the "8-hour time-weighted average" by the corresponding "Excursion Factor" as specified in the following Attachment. This concentration is the level at or below which it is believed that workers may be continuously exposed for any 15-minute period without suffering from unbearable irritation, chronic or irreversible tissue damage, narcotic or fainting effects, increased risk of accidents, or reduction in work efficiency.3. Ceiling limit: An employee's exposure to any substance designated as “Ceiling” in Attachment 1 shall not exceed the Ceiling limit specified therein at any time during exposure, to prevent the employee from suffering from unbearable irritation or physical impairment.Appendix 1 Permissible Exposure Limits of Hazardous Substances in Air.pdfAppendix 2 Permissible Exposure Limits of Dusts in Air.pdfArticle 3.pdf