  Interstellar gas heating is a powerful cosmology-independent observable for
exploring the parameter space of primordial black holes (PBHs) formed in the
early Universe that could constitute part of the dark matter (DM). We provide a
detailed analysis of the various aspects for this observable, such as PBH
emission mechanisms. Using observational data from the Leo T dwarf galaxy, we
constrain the PBH abundance over a broad mass-range, $M_{\rm PBH} \sim
\mathcal{O}(1) M_{\odot}-10^7 M_{\odot}$, relevant for the recently detected
gravitational wave signals from intermediate-mass BHs. We also consider PBH gas
heating of systems with bulk relative velocity with respect to the DM, such as
Galactic clouds.
