| Date | Value |
|---|---|
| Nov 27, 2017 08:43 | 510 ppm |
| Jan 28, 2016 18:34 | 420 ppm |
| Jan 12, 2016 12:59 | 442 ppm |
| Dec 26, 2015 18:58 | 350 ppm |
| Oct 8, 2015 16:51 | 397 ppm |
| Sep 3, 2015 19:54 | 380 ppm |
| Aug 31, 2015 11:15 | 515 ppm |
| Jul 1, 2015 20:18 | 350 ppm |
| Mar 31, 2015 11:55 | 450 ppm |
| Mar 1, 2015 19:02 | 470 ppm |
| Feb 21, 2015 14:32 | 420 ppm |
| Sep 29, 2014 21:18 | 370 ppm |
| Sep 6, 2014 19:45 | 390 ppm |
| Jul 11, 2014 20:52 | 375 ppm |
| May 22, 2014 20:52 | 320 ppm |