Performance of Single Point Monitors (SPMs) was evaluated for measuring aerial ammonia (NH3 ) and hydrogen sulfide (H2 S) under laboratory and field conditions. Calibration gas or NH3 /H2 S-ladden air at various dew-point temperatures (tdp ) were introduced simultaneously to the SPMs under evaluation and a chemiluminescence NH3 analyzer or a pulsedfluorescence H2 S analyzer. Linear relationships were found between readings of the SPMs and those of the respective gas analyzer. Moisture in the air positively influenced the SPM readings. The SPM readings for H2 S measurement can be corrected to achieve 90% to 107% agreement with the analyzer readings. However, such corrections proved not as effective for NH3 measurements (59% to 90% agreement). To improve quality of H2 S data obtained with SPMs, moisture content of the sample air should be concurrently measured and its effect on output readings compensated.