Ambient air is an important matrix for the effectiveness evaluation of the Convention because it has a very short response time to changes in atmospheric emissions and is a relatively well-mixed environmental medium and includes both chemicals in gaseous form as well as chemicals partitioned onto particles (UNEP, GMP guidance 2019). The objective of the ambient air sampling networks under the SC Global Monitoring Plan (GMP) is to obtain representative data for assessing baselines, changes over time and space and the regional and global transport of Persistent Organic Pollutants (POPs).