An independent auditor visits each CASTNET site at least once every other year to perform a Field Systems Audit (FSA). Regulatory ozone monitoring sites are audited annually by an independent auditor or a local monitoring agency. Performance evaluation results are loaded into EPA's Air Quality System (AQS) database routinely.

The Quality Assurance Project Plan (QAPP) and Standard Operating Procedures for the independent audits are available below. The quarterly and annual audit reports are also provided below.
 

• First Quarter Audit Report - 2020 (PDF)(41 pp, 380 K)
• Fourth Quarter Audit Report - 2019 (PDF)(454 pp, 3 MB)
• Third Quarter Audit Report - 2019 (PDF)(520 pp, 3 MB)
• Second Quarter Audit Report - 2019 (PDF)(261 pp, 2 MB, 8/28/2019)
• First Quarter Audit Report - 2019 (PDF)(98 pp, 969 K, 4/15/2019)
• CASTNET Annual Report - 2018 (PDF)(75 pp, 7 MB)
• Fourth Quarter Audit Report - 2018 (PDF)(335 pp, 2 MB, 4/1/2019)
• Third Quarter Audit Report - 2018 (PDF)(287 pp, 1 MB, 12/20/2018)
• Second Quarter Audit Report - 2018 (PDF)(309 pp, 1 MB, 7/20/2018)
• First Quarter Audit Report - 2018 (PDF)(35 pp, 312 K, 4/20/2018)
• CASTNET Annual Report - 2017 (PDF)(86 pp, 11 MB)
• Fourth Quarter Audit Report - 2017 (PDF)(395 pp, 2 MB, 2/14/2017)
• Third Quarter Audit Report - 2017 (PDF)(483 pp, 2 MB, 10/14/2017)
• Second Quarter Audit Report - 2017 (PDF)(303 pp, 2 MB, 6/20/2017)
• First Quarter Audit Report - 2017 (PDF)(204 pp, 1 MB, 4/24/2017)
• CASTNET Annual Report - 2016 (PDF)(121 pp, 7 MB)
• Fourth Quarter Audit Report - 2016 (PDF)(228 pp, 1 MB, 2/28/2017)
• Third Quarter Audit Report - 2016 (PDF)(275 pp, 1 MB, 10/24/2016)
• Second Quarter Audit Report - 2016 (PDF)(215 pp, 1 MB, 7/12/2016)
• Audit Program Annual Report - 2015 (PDF)(77 pp, 7 MB, 6/15/2016)
• Fourth Quarter Audit Report - 2015 (PDF)(314 pp, 9 MB, 1/6/2016)
• Third Quarter Audit Report - 2015 (PDF)(442 pp, 4 MB, 10/12/2015)
• First Quarter Audit Report - 2015 (PDF)(178 pp, 1 MB, 5/1/2015)
• Audit Program Annual Report - 2014 (PDF)(56 pp, 4 MB, 7/13/2016)
• Fourth Quarter Audit Report - 2014 (PDF)(219 pp, 2 MB, 6/9/2016)
• Third Quarter Audit Report - 2014 (PDF)(383 pp, 2 MB, 5/12/2016)
• Second Quarter Audit Report - 2014 (PDF)(244 pp, 3 MB, 5/5/2016)
• First Quarter Audit Report - 2014 (PDF)(190 pp, 1 MB, 5/3/2016)
• Audit Program Annual Report - 2013 (PDF)(64 pp, 7 MB, 2/1/2015)
• Third Quarter Audit Report - 2013 (PDF)(312 pp, 2 MB, 8/1/2014)
• Second Quarter Audit Report - 2013 (PDF)(377 pp, 2 MB, 7/1/2013)
• First Quarter Audit Report - 2013 (PDF)(270 pp, 2 MB, 5/1/2013)
• Audit Program Annual Report - 2012 (PDF)(56 pp, 12 MB, 3/1/2014)
• Audit Program Annual Report - 2011 (PDF)(33 pp, 212 K, 4/1/2012)
• Audit Program Annual Report - 2007 (PDF)(40 pp, 216 K, 3/10/2008)
• Audit Program Annual Report - 2006 (PDF)(38 pp, 232 K, 3/12/2007)
• Audit Program Annual Report - 2005 (PDF)(31 pp, 189 K, 2/28/2006)
• Audit Program Quality Assurance Project Plan (QAPP) (PDF)(34 pp, 372 K, 7/1/2007)
• Audit Program Standard Operating Procedures (SOPs) (PDF)(60 pp, 398 K, 8/1/2005)