  The exquisite capabilities of liquid Argon Time Projection Chambers make them
ideal to search for weakly interacting particles in Beyond the Standard Model
scenarios. Given their location at CERN the ProtoDUNE detectors may be exposed
to a flux of such particles, produced in the collisions of 400 GeV protons
(extracted from the Super Proton Synchrotron accelerator) on a target. Here we
point out the interesting possibilities that such a setup offers to search for
both long-lived unstable particles (Heavy Neutral Leptons, axion-like
particles, etc) and stable particles (e.g. light dark matter, or millicharged
particles). Our results show that, under conservative assumptions regarding the
expected luminosity, this setup has the potential to improve over present
bounds for some of the scenarios considered. This could be done within a short
timescale, using facilities that are already in place at CERN, and without
interfering with the experimental program in the North Area.
