Typical searches for supersymmetry cannot test models in which the two
lightest particles have a small ("compressed") mass splitting, due to the small
momentum of the particles produced in the decay of the second-to-lightest
particle. However, datasets with large missing transverse momentum (ETmiss) can generically search for invisible particle production and
therefore provide constraints on such models. We apply data from the ATLAS
mono-jet (jet+ETmiss) and vector-boson-fusion (forward jets and
ETmiss) searches to such models. The two datasets have
complementary sensitivity, but in all cases experimental limits are at least
five times weaker than theoretical predictions