| Date | Value |
|---|---|
| Aug 17, 2013 23:27 | 440 ppm |
| Jul 26, 2013 18:12 | 320 ppm |
| Jul 21, 2013 16:03 | 300 ppm |
| Jun 29, 2013 15:44 | 400 ppm |
| Jun 22, 2013 10:18 | 480 ppm |
| Jun 15, 2013 16:37 | 420 ppm |
| Jun 7, 2013 19:45 | 400 ppm |
| May 31, 2013 18:15 | 340 ppm |
| Apr 28, 2013 08:47 | 360 ppm |