The intent has been to allow as much flexibility as possible in the physical construction of the experimental apparatus. Therefore, only those portions of the apparatus whose operation is critical to the accurate measurement of emissions levels are prescribed in detail.
An engine test procedure including a test sequence is outlined such that it would cover the various applications in which small engines are used. The intent is to provide an understanding of the levels of exhaust emissions and does not imply that in given application, an engine would operate in all the modes outlined in the test sequence. Depending upon the engine and/or its application, only those modes which are appropriate need to be used.