Brillouin scattering in gas shows unmatched gain properties in hollow-core optical fibers filled at high pressure. Here, the gain characteristics are studied for two common gases, namely, N2 and CO2, which show distinct features and are compared to expected responses deduced from conventional thermodynamic models for gases. This is realized—for the first time to our knowledge—in anti-resonant hollow-core optical fibers, demonstrating their full suitability for generating and exploiting Brillouin amplification in fluidic media. The potential of Brillouin scattering in gases is manifested in a distributed temperature sensor that is totally immune to strain and benefits from the absence of shear stress in the gaseous medium. The experimental results presented indicate that gases with smaller molecular masses show a higher temperature sensitivity than gases with larger masses. This inverse proportionality between the temperature sensitivity and the molecular mass of a gas shown in the experiment qualitatively agrees with the ideal gas model.