| Date | Value |
|---|---|
| Mar 11, 2015 03:07 | 400 ppm |
| Mar 4, 2015 02:20 | 400 ppm |
| Mar 1, 2015 15:30 | 410 ppm |
| Feb 22, 2015 17:05 | 400 ppm |
| Feb 16, 2015 15:36 | 420 ppm |
| Feb 16, 2015 14:35 | 370 ppm |
| Feb 15, 2015 06:53 | 360 ppm |
| Jan 18, 2015 17:31 | 410 ppm |
| Jan 4, 2015 13:10 | 440 ppm |
| Dec 27, 2014 12:54 | 440 ppm |