There is considered in the article a problem of geo-ecological risk assessment of atmospheric air pollution by gas emissions from municipal solid waste (MSW) landfills. It has been shown that in the case of absence of full-scale data about MSW landfills conditions it is expedient to use methods of mathematical modeling of gas emissions formation and their distribution in atmospheric air when natural decomposing waste, and also in case of fires. The carried out assessment of risks of atmospheric air pollution by harmful substances from operating landfill confirms a danger for the population living near to a sanitary zone of landfill even from diffusive emissions of biogas. This danger sharply increases in a case of ignition of waste. It confirms necessity of construction of biogas collection and utilization system when scheduling aftercare works at landfill for the purpose of minimization of geo-ecological risk of pollution of atmospheric air and occurrence of fires.