As the output of the CSN and IMPROVE Protocol Assessments, five recommendations were made and ultimately implemented. Feedback was received and incorporated from EPA management and regional staff, state and local monitoring agencies, and university, research and local communities.

• The CSN mass measurement was widely used when the network was established.
• Now, the FRM mass measurement is widely used for model attainment, model evaluation, design values, and other purposes.
• The majority of the CSN sites have an FRM that is also providing a PM_2.5 mass measurement.*
• Extensive analysis has been conducted demonstrating that the CSN and FRM PM_2.5 mass measurements compare well. Any differences in the measurement can primarily be explained by the differences in the measurement techniques (e.g., sample volume, sampler design, etc.)
• A QA check can still be conducted by performing a mass balance and comparing to the FRM PM_2.5 mass measurement.
• Additional information regarding the comparison of these methods can be found here.
• The CSN PM_2.5 mass measurement was eliminated in October 2014 (last sample collected September 29^th).

*The few sites that do not have FRMs will continue the CSN PM_2.5 mass measurement until such time as an FRM is established.

• Sample frequency was reduced to 1-in-6 at CSN Supplemental sites that are not NCore or STN in January 2015 (Arnold West, MO, Wylam, AL and Albany, NY).

• Carbon backup filter blanks were eliminated in January 2015.
• The number of field blank filters were reduced to the lowest level needed to adequately support organic carbon (OC) artifact correction for the CSN.
• As of February 2015, carbon field blanks are collected at 26 representative 1-in-3 day CSN sites and 23 representative 1-in-6 day CSN sites at a frequency of 1 per month.
• The full report on the recommendations for field blank collection for the CSN can be found here.
• UPDATE: starting in March of 2017, field blanks for all filter types (including carbon) are now collected at a frequency of 1 per month at all CSN sites.

• The number of icepacks included in sample shipments was reduced in October 2014 from 8 to 6 during the cooler months of the year (October 1 - March 31).

• After incorporating scoring, intangibles, and feedback from stakeholders, 38 CSN sites were defunded by January 2015 and 8 IMPROVE Protocol sites were defunded by January 2016.