‘Sec. 6. 38 MRSA §589, sub-§2, as enacted by PL 1991, c. 384, §9 and affected by §16, is amended to read:
2. Stack tests. A person is not required to conduct stack tests for chlorine or chlorine dioxide more frequently than once every 5 years unless visible emissions, operating parameters or other information indicates the source may be operating out of compliance with any applicable emission standard or unless there are more stringent federal requirements. A person is not required to conduct stack tests for particulate matter on a source monitored by a continuous monitoring device for opacity as specified by 40 Code of Federal Regulations, Part 60, Appendix B, specification 1 or appropriate surrogate parameters as required by the commissioner more frequently than once every 2 5 years unless visible emissions, operating parameters or another cause other information indicates the source may be operating out of compliance with any applicable emission standard or unless there are more stringent federal requirements. If visible emissions, operating parameters or other information indicates potential noncompliance with an air emission standard or if there are more stringent federal requirements, the department may require additional stack tests.’