An earlier experience of explosion within the vertical muffler had led me to believe that LPG forklifts must be offered with a horizontal muffler only. the rationale being that the unused leaked gas accumalates in the muffler when the forklift is not in use & when the engine starts the gas may get ignited(by sparks) in the constrained space of the muffler and eventually explode. Is this thinking right? secondly I have seen a few Daewoo trucks in India with vertical exhausts and was wondering whether this is wise.