Odor Threshold 4 : The minimum concentration of a substance in the air at which a majority of test subjects can detect and identify the substance's characteristic odor
United States Department of Labor, Occupational Safety & Health Administration (OSHA), Personal Protective Equipment Glossary (OSHA 29 CFR 1910.132), Washington, DC USA 2012. http://www.osha.gov/dte/grant_materials/fy07/sh-16 625-07/ppeglossary3.pdf, (OSHA/ Pers Prot Equip - Amer) {498}