Method of measurement

1. Method 9. Compliance with visible emission standards in chapter 33.1-15-03 shall be determined by conducting observations in accordance with Reference Method 9 of Appendix A to chapter 33.1-15-12. Per hour for Reference Method 9 means any contiguous sixty-minute time period. When Reference Method 9 opacity readings are not available, continuous opacity monitors may be substituted. Per hour for monitors means any sixty-minute period commencing on the hour. The results of continuous monitoring by transmissometer, which indicate that the opacity at the time visible emissions were taken, were not in excess of the standard, are probative but not conclusive evidence of the actual opacity of an emission; provided, that the source shall meet the burden of proving that the instrument used meets (at the time of the alleged violation) Performance Specification 1 in Appendix B, has been properly maintained and (at the time of the alleged violation) calibrated, and that the resulting data have not been tampered with in any way. 2. Method 22. When a visible emissions limit is specified in a permit issued in accordance with this article as zero percent opacity except for a certain frequency, compliance shall be determined using Reference Method 22 of Appendix A to chapter 33.1-15-12.