⁵⁹This particular interference compound is especially problematic if we are using the analyzer to control the NO_x concentration in the exhaust of a combustion process, and the manipulated variable for the NO_x control loop is pure ammonia injected into the exhaust. Un-reacted ammonia (commonly called ammonia slip in the industry) sampled by the analyzer will be falsely interpreted as NO_x, rendering the measurement meaningless, and therefore making control virtually impossible.