The LHCb experiment, designed for $b$-physics, introduced SMOG (\emph{System for Monitoring the Overlap with Gas}) in 2015 to improve the luminosity measurements studying the beam profile through the collisions of the LHC protons with gas atoms injected in the beam--pipe.
Proton--gas collisions are used today to study production cross-sections in fixed--target mode, exploring a kinematic region otherwise unaccessible. In this contribution, I review the programme and present recent measurements on the production of heavy flavours in \pAr collisions and production of \antiprotons in \pHe collisions. The latter will contribute to reduce the dominant contribution to the uncertainty on the theoretical predictions of the \antiproton flux in primary cosmic rays, an excess of which would represent evidence for New Physics.