The detection of moving droplets is essential in food, energy, mining, and chemical industries. Portable radars are an emerging technology for the detection, identification, and monitoring of aerosol. However, existing works only rely on the Doppler effect caused by the motion of micrometer-size solid particles in the sensor’s field of view. Besides, the detection is done by non-portable radar systems. In this paper, the feasibility of using sub-THz portable Doppler radar technology to monitor the presence of randomly moving liquid aerosol is investigated. Experimental results demonstrate the effectiveness of the proposed technique.