| Date | Value |
|---|---|
| Dec 31, 2015 07:50 | 1310 ppm |
| Dec 2, 2015 11:31 | 1215 ppm |
| Sep 16, 2015 11:49 | 1215 ppm |
| May 7, 2015 10:38 | 1300 ppm |
| Apr 6, 2015 06:38 | 1360 ppm |
| Mar 25, 2015 11:40 | 1350 ppm |
| Mar 13, 2015 06:58 | 1290 ppm |
| Mar 8, 2015 09:54 | 1260 ppm |
| Mar 1, 2015 07:15 | 1200 ppm |
| Feb 27, 2015 10:41 | 1180 ppm |