| Date | Value |
|---|---|
| Mar 11, 2013 00:22 | 0.00 ppm |
| Feb 28, 2013 22:22 | 0.01 ppm |
| Feb 23, 2013 08:29 | 0.00 ppm |
| Feb 20, 2013 06:50 | 0.01 ppm |
| Feb 17, 2013 21:54 | 0.01 ppm |
| Feb 13, 2013 17:07 | 0.03 ppm |
| Feb 9, 2013 06:10 | 0.03 ppm |
| Feb 4, 2013 06:10 | 0.15 ppm |
| Jan 30, 2013 06:09 | 0.50 ppm |