The Toolkit emission factors for open burning were significantly revised since the 2005 edition, and new source classes added to the respective categories. These two factors will most likely trigger the need to revise baseline estimates in most cases. In addition, reviewing the approach that was used in the baseline inventory provides useful information on how to estimate activity rates for this source group. Data on open burning is very limited at the country level, and expert judgment will be needed to fill such gaps. Checking the assumptions made in the baseline inventory to estimate activity rates and applying the same assumptions in the updated inventory equally enables obtaining consistent results and coherent trends in releases over time.