| Value | Date |
|---|---|
| 380 ppm | Aug 20, 2012 20:28 |
| 425 ppm | Aug 5, 2012 15:19 |
| 415 ppm | Aug 3, 2012 20:13 |
| 430 ppm | Jul 28, 2012 19:45 |
| 430 ppm | Jul 25, 2012 20:51 |
| 415 ppm | Jul 21, 2012 21:28 |
| 420 ppm | Jul 20, 2012 20:48 |
| 450 ppm | Jul 14, 2012 20:16 |
| 430 ppm | Jul 7, 2012 21:26 |
| 440 ppm | Jun 30, 2012 21:37 |
| 470 ppm | Jun 24, 2012 14:38 |
| 500 ppm | Jun 17, 2012 20:25 |
| 490 ppm | Jun 10, 2012 17:34 |
| 560 ppm | May 8, 2012 22:53 |
| 530 ppm | Apr 29, 2012 20:02 |
| 450 ppm | Jan 8, 2012 16:57 |