| Date | Value |
|---|---|
| Apr 2, 2013 20:33 | 390 ppm |
| Mar 2, 2013 17:37 | 420 ppm |
| Feb 10, 2013 06:07 | 400 ppm |
| Jan 1, 2013 20:32 | 420 ppm |
| Dec 1, 2012 12:40 | 400 ppm |
| Nov 5, 2012 18:49 | 450 ppm |
| Oct 1, 2012 21:54 | 430 ppm |
| Sep 3, 2012 20:00 | 430 ppm |
| Aug 31, 2012 14:35 | 450 ppm |
| Aug 6, 2012 22:18 | 460 ppm |
| Jul 30, 2012 21:43 | 410 ppm |
| Jul 20, 2012 11:51 | 430 ppm |