This section describes the requirements for chemiluminescent detectors (CLD) used to measure NOX. Good engineering practice may require the use of other detectors.

(a) A CLD must meet the following requirements:

(1) Make sure your CLD meets the accuracy and precision specifications in ISO 8178-1 (incorporated by reference in §1065.1010).

(2) The NO to NO2 converter must have an efficiency of at least 90 percent.

(3) Use an overflow sampling system for continuous CLDs. (In an overflow system excess zero gas or span gas spills out of the probe when you are doing zero or span checks.)

(4) You do not need a heated CLD to test spark-ignition engines.

(b) Using CLDs is generally acceptable even though they measure only NO and NO2, since conventional engines do not emit significant amounts of other NOX species.