The article presents selected problems concerning tests of toxic exhaust emissions from engines of vehicles, mobile devices, engines used in gardening and construction works. For this group of engines, this type of testing is carried out primarily in laboratory conditions, however, variable load conditions during actual operation justify efforts to determine the level of emissions in real operating conditions. Research in real operating conditions for different engine categories becomes increasingly more standard, in this aspect, it is necessary to verify the state of knowledge and methodology in the aspect of testing engines of machines and mobile devices. The research performed by the authors was the first of this type using PEMS equipment, hence some conclusions and observations can be made from the obtained results. At present, the type approval procedures for the engine group in question do not account for emissions tests in real operating conditions, while also missing any description of a standardized research methodology. In addition, the engine group in question is not really suitable for testing in real conditions. An introduction to research aimed at developing an exhaust emission test methodology in real operating conditions of mobile device engines was included in the article.