This document discusses the importance of accurate air emissions inventories. It notes that emissions inventories are used for air quality modeling, health impact assessments, and developing pollution control strategies. However, emissions are often uncertain by a factor of two or more. Inaccurate data can lead to ineffective pollution control plans. The document examines sources of error in emissions estimation methods and factors. It emphasizes that accurate emissions data is needed to underpin effective air quality management and that a collaborative effort is required between all stakeholders to improve emissions estimation methods and ensure data quality.