Depending on the tier applied, operator sets calculation factors, used to determine emissions, as default values or values based on analysis. If operator sets calculation factors as default values, then, in accordance with requirements for the appropriate tier level specified in Commission Regulation (EU) No 601/2012 of 21 June 2012 on the monitoring and reporting of greenhouse gas emissions pursuant to Directive 2003/87/EC of the European Parliament and of the Council, he may use factors used by the Member State in the national inventory forwarded to the Secretariat of the United Nations Framework Convention on Climate Change. In case of Poland default values of the factors are collected in the Net Caloric Value and Emission Factors Tables containing data on net caloric values and emission factors for fuels used in the national economy during a given year, prepared on the basis of the greenhouse gas emissions national inventory.