| Date | Value |
|---|---|
| Oct 27, 2017 13:04 | 0.05 ppm |
| Aug 8, 2017 19:41 | 0.00 ppm |
| May 15, 2017 17:26 | 0.00 ppm |
| Mar 13, 2016 14:59 | 0.00 ppm |
| Jun 21, 2015 14:55 | 0.05 ppm |
| May 12, 2015 14:05 | 0.00 ppm |
| Mar 21, 2015 10:14 | 0.50 ppm |
| Feb 12, 2015 10:24 | 0.00 ppm |
| Jan 29, 2015 12:50 | 1 ppm |