Engine compartments of heavy vehicles are, in general, spaces where detecting fires with inexpensive and simple fire detection systems is arduous. High temperatures, high airflows, complicated geometries, large amounts of soil, dust and pollutants, and the wide range of surface temperatures, complicate the operation of all types of detectors. More advanced fire detection systems will, on the other hand, have durability issues caused by vibration, shocks, temperature variations and corrosion. SP Fire Research has developed a new test method to evaluate the detection performance as well as the durability of detection systems installed in engine compartments of heavy vehicles. A standardised test method would mean that only efficient detection systems are placed in service. SP Fire Research has worked over two years analysing engine compartments and fire scenarios from a fire detection point of view, including pre-tests of different fire detection systems. This article gives an overview of the challenges of heavy vehicle engine compartments with respect to fire detection and an outline of the new test method.