A short cruising range is known to be one of the main disadvantages of electric buses. In cold climate regions, running an electric heater can consume more than 50% of the battery's total energy, which significantly affects the range. Installing a liquid heater that operates on diesel fuel can considerably compensate for this disadvantage, however, the use of such a system is associated with the presence of emissions of combustion products that can penetrate into the passenger compartment. The purpose of the study is to determine the emissions of harmful substances in the exhaust gases of a diesel heating installation and to determine the interior air quality parameters of the KAMAZ-6282 electric bus when this heater is operating. The study was performed in compliance with the requirements of GOST 33554-2015 and UNECE Regulation No. 122. The study presents the results of testing for emission of harmful substances with exhaust gases of an electric bus diesel heater. Compliance with the GOST 335542-015 requirements in terms of interior air quality has been determined. A comparison of specific emissions with other types of vehicles is presented. The results of this study can be used to improve the environmental performance of electric passenger transport.