A new method is proposed to compare the sensitivity of uncooled metal bolometers. This method allows us to conduct a comparative analysis for the sensitivity of uncooled bolometers with metal and metal alloy resistive elements. The experiments showed a twofold superiority in the sensitivity of the TiNi alloy-based bolometer with a resistive element less than $10~\Omega $ in resistance over the identical bolometers based on technologically applicable metals due to improved electrophysical properties. The Ti50.5Ni49.5 bolometer developed to measure the total solar radiation has a higher sensitivity, a higher measuring efficiency, a smaller weight, and size compared with a serial CMP-11 pyranometer, as well as the best environmental protection. The highly sensitive uncooled metal bolometers are shown to be used as an integral part of the optical absorption gas analyzer to provide the control of background mercury vapors in the atmosphere.