AQS will NOT be available from Saturday, 1/15/11, 7 am ET to Sunday, 1/16/11, 5pm ET. We regret any inconvenience.

The "AQS Technical Note – NAAQS Reporting Issues for NO2 and SO2, NCore Reporting Issues for NOy and trace-level gases - November 3, 2010" stated that the standard units for NO2 and SO2 had changed from ppm to ppb. To be consistent, the standard units for NO2 and SO2 related parameters will also be changed from ppm to ppb, and it is the conversion for these parameters that will take place this weekend.

• Standard units for the following will now be ppb (code 008): Reactive oxides of nitrogen (NOy) - 42600

Nitric oxide (NO) - 42601

Oxides of nitrogen (NOx) - 42603

SO2 max 5-min avg - 42406

The summaries (Daily, Quarterly and Annual) for these will also be recomputed.

Regards,

Angie Shatas

US EPA 919-541-5454 shatas.angie@epa.gov