| Date | Value |
|---|---|
| Aug 20, 2020 20:17 | 24 ppm |
| Jun 26, 2020 19:01 | 16 ppm |
| May 10, 2020 20:26 | 16 ppm |
| Apr 25, 2020 19:11 | 24 ppm |
| Apr 5, 2020 18:48 | 12 ppm |
| Dec 15, 2019 11:52 | 14 ppm |
| Dec 5, 2019 21:04 | 4 ppm |
| Dec 2, 2019 18:34 | 1.5 ppm |
| Nov 19, 2019 17:58 | 0.60 ppm |
| Nov 10, 2019 08:04 | 0.25 ppm |
| Nov 7, 2019 07:59 | 0.75 ppm |
| Nov 5, 2019 07:59 | 4 ppm |