| Date | Value |
|---|---|
| Aug 12, 2017 19:05 | 1425 ppm |
| May 30, 2017 15:35 | 1350 ppm |
| May 9, 2017 13:44 | 1350 ppm |
| Mar 24, 2017 12:57 | 1320 ppm |
| May 8, 2016 16:42 | 1380 ppm |
| Feb 1, 2016 12:27 | 1410 ppm |
| Aug 27, 2015 12:15 | 1425 ppm |
| Aug 1, 2015 16:56 | 1305 ppm |
| May 17, 2015 16:15 | 1410 ppm |
| Jan 21, 2015 12:03 | 1400 ppm |
| Nov 15, 2014 10:50 | 1380 ppm |