Air can become stratified in a standard mushroom tunnel using a single-duct air distribution system. Stratification can be overcome by increased air circulation, such as the addition of a secondary air distribution duct, i.e., a boost duct air distribution system. To compare the performance of both systems, this study measured the spatial variation in climate for both systems. Air temperature, humidity, and speed were monitored at representative locations in one-half of the tunnel, as bilateral symmetry in air distribution has been previously observed. The experiments, including replicates, were conducted for both full recirculation and fill fresh air A vertical mean air temperature difference of 0.22 deg C was observed for the boost air distribution system and 2.22 deg C for the single air distribution system. No significant longitudinal difference was observed for either system. The lower vertical air temperature difference of the boost system shows its superior mixing performance.