This part of IS0 8178 specifies two methods for the measurement of exhaust gas smoke characteristics of reciprocating internal combustion (RIG) engines operating under steady-state conditions. One method evaluates smoke opacity by measurement of the obscuration of a light beam; the other evaluates the soot content by measurement of the blackening of a filter. Where necessary, individual requirements may be specified for particular engine applications. This part of IS0 8178 does not deal with measurement under transient conditions; if smokemeters are used under transient conditions, the results from different types of instrument cannot be compared unless the sampling conditions are identical and the instrument characteristics are compatible. This part of IS0 8178 is applicable to RIC engines for land, rail-traction and marine use, including engines used to propel agricultural tractors and road vehicles. It may be applied to engines used to propel roadconstruction and earth-moving machines, industrial trucks, and for other applications where no suitable International Standards for exhaust gas smoke measurement of these engines exist.