The Air Quality Division conducted a 2011 Engine Emissions Study to independently evaluate emission data from engines operating around the state. Five week-long studies were conducted in a representative cross-section of the state. A test firm was contracted by the Division to evaluate emissions from selected engines in an as-found condition. Initially, portable analyzer testing was planned following the Air Quality Division's Portable Analyzer Monitoring Protocol. However, due to reliability issues and high pollutant concentrations, the use of portable analyzer equipment was discontinued midway through the second campaign. Reference method equipment was used for the remainder of the study.