Based on research performed by Ontario Hydro Technologies, Tyne Engineering has developed a surface activity monitor (SAM) for tritium. This paper reports the results of experiments carried out to characterize the ability of this device to measure tritium activity on smear paper, on flat surfaces and in water. The characterization of the SAM involves measuring the minimum detection limit, the linearity, and the settling time after a disturbance. Experimental evidence is presented to show that SAM is an effective tool for smear, direct surface contamination, and tritiated water measurements. In addition, preliminary results are presented to demonstrate the potential for monitoring surfaces contaminated with alpha emitters.