The research had the following objectives: to assess the efficiency of a collector and the reliability of the applied parameters such as the outlet air velocity, temperature increase depending on the intensity of solar irradiance, the influence of ambient temperature on the collector's efficiency and heat loss. The solar-air collector (1180 mm x 610 mm x 77 mm (height, width, depth)) was installed vertically on a South-faced wall and exposed to solar irradiance. The following parameters were measured in the course of study: intensity of solar irradiance falling on a vertical surface (the collector was installed in a vertical position according with the producer design), temperature and velocity of air flowing into the collector as well as the temperature and velocity of air flowing out of the device. The study indicates that the collector worked efficiently at an irradiance value of just 100 Wm(-2) and heated up the flowing air by about 5 degrees C. This temperature increased together with increasing irradiance and reached the value of 20 degrees C at the irradiance value of 800 Wm(-2). The analysis of the collector's efficiency showed that during its work (proper temperature and irradiance) the efficiency remained at a satisfactory level from 42 to 46%.