Modified Active Gas Sampling (MAGS) is an environmental engineering assessment technique which rapidly detects unsaturated soil source areas impacted by volatile organic compounds. The technique was developed by HSA Engineers & Scientists in Fort Myers, Florida in 2002, led by Richard Lewis, Steven Folsom, and Brian Moore. It is being used all over the United States, and has been adopted by the state of Florida in its Dry-cleaning Solvent Cleanup Program.