Direct Measurement of Ammonia in Ambient Air

A model is proposed which addresses the factors involved in the axial light attenuation of a coated waveguide (collector/sensor) whose polymer coating has been sensitized to ammonia. The experimental results appear to corroborate the model predictions of high sensitivity (ppb) and independence of sample flow on the collector/sensor. Concentration and relative humidity both determine the slopes of the transmission curves, the latter factor of which can be reduced to a second order effect by controlling the relative humidity in the sample holder.