| Date | Value |
|---|---|
| May 11, 2014 06:26 | 440 ppm |
| May 4, 2014 07:06 | 480 ppm |
| Apr 22, 2014 07:10 | 450 ppm |
| Apr 21, 2014 13:43 | 450 ppm |
| Apr 13, 2014 07:22 | 460 ppm |
| Mar 29, 2014 11:57 | 430 ppm |
| Mar 23, 2014 06:47 | 440 ppm |
| Mar 21, 2014 11:15 | 420 ppm |
| Mar 15, 2014 08:12 | 420 ppm |
| Mar 2, 2014 08:41 | 380 ppm |