Verification testing began on two technology categories in April-ambient hydrogen sulfide analyzers (H2S) and mercury continuous emission monitors (CEMS). Both technologies detect important hazardous pollutants in the air. The tests are being conducted by Battelle, which manages the U.S. EPA’s Environmental Technology Verification (ETV) Program’s Advance Monitoring Systems (AMS) Center. The AMS Center conducts verification testing of monitoring technologies for contaminants and natural species in air, water, and soil.