The overall objective of the project is to improve ambient air quality in Sofia Municipality by reducing PM10 emissions from domestic heating as one of the main sources of air pollution. The specific objective of the project is to replace solid fuel heating devices of households with environmental alternatives. The project will be implemented in two phases. In the first phase, all preparatory actions necessary to carry out the investment will be carried out. A public awareness campaign will be held on the possibilities for replacing solid fuel heating devices, explaining the possible alternative forms of heating and the conditions for including those who wish to join the replacement scheme. There will be a survey among those residents who are heated with solid fuel to replace the heating devices they use. Analyses, criteria and mechanisms for the prioritisation of households by region/district will be prepared when alternatives are applied with a view to contributing to the reduction of PM10 emissions. The actual technical parameters for replacing the devices will be examined. During the second stage, Sofia Municipality will conduct procedures for the selection of contractors and will perform disassembly of the used heating devices and supply and installation of the new heating devices/systems according to the adopted parameters, or connection/restore of the connection to the gas distribution network and/or district heating system. The environmental benefits of the project will be expressed in a quantity of PM10 emissions saved. The socio-economic benefits are related to health protection and improvement of the quality of life of the residents of Sofia Municipality, improvement of working and recreational conditions for both residents and guests of the municipality, raising public awareness of air quality issues.