| Date | Value |
|---|---|
| Oct 9, 2016 11:57 | 1320 ppm |
| Jul 10, 2016 14:09 | 1680 ppm |
| May 15, 2016 09:41 | 1200 ppm |
| May 3, 2016 18:25 | 1080 ppm |
| Apr 2, 2016 15:37 | 1160 ppm |
| Jan 16, 2016 15:58 | 1200 ppm |
| Sep 7, 2015 12:27 | 1360 ppm |
| Aug 8, 2015 16:34 | 1300 ppm |
| Aug 1, 2015 13:09 | 1280 ppm |
| Jun 21, 2015 16:53 | 1240 ppm |
| Jun 14, 2015 16:05 | 1280 ppm |
| Jun 6, 2015 18:04 | 1280 ppm |