The detailed test procedures outlined in this recommended practice consist of two general types of tests. These tests are of the bench type and a full scale engine type test, which exposes the smokemeter to the environment (exhaust gases) that the meter ultimately must perform in if it is to be of practical use. The bench type tests consist of two general types. The first series of bench tests are used to assess the basic optical and electrical characteristics of the instrument. The second series of bench tests are used to evaluate the effect of a simulated operating environment (temperature, light, and vibration) on the smokemeter. Finally, performance limits for the various types of smokemeters and for various smoke concentrations are established based on the bench and engine performance tests outlined above.

This recommended practice does not develop the various instrumental techniques for measuring smoke since these are contained in SAE Information Report - SAE J255 (1). The background data supporting this recommended practice is contained in References (2) and (3). SAE Recommended Practice J35 (4) contains guidelines for running engine tests with developed full-flow light extinction type smokemeters.