| Date | Value |
|---|---|
| May 18, 2012 21:00 | 0.00 ppm |
| May 11, 2012 17:58 | 0.00 ppm |
| May 4, 2012 21:45 | 0.00 ppm |
| Apr 27, 2012 11:09 | 0.00 ppm |
| Apr 20, 2012 14:34 | 0.00 ppm |
| Apr 17, 2012 14:34 | 0.00 ppm |
| Apr 13, 2012 15:30 | 0.00 ppm |
| Apr 10, 2012 13:10 | 0.00 ppm |
| Apr 6, 2012 13:06 | 0.10 ppm |
| Mar 30, 2012 15:21 | 3.3 ppm |
| Mar 23, 2012 20:39 | 3.3 ppm |