This International Standard specifies the characteristics required for apparatus to measure the soot content from the exhaust gas of reciprocating internal combustion compression-ignition (diesel) engines operating under steady-state conditions according to the method of blackening a filter. These measuring apparatus are called "Filter-Type Smokemeters". This International Standard does not deal with apparatus for measurement under transient conditions; if filter-type smokemeters are used under transient conditions, the results of different types of instruments cannot be compared unless sampling conditions are identical. This International Standard does not apply to engines for aircraft.