Let R be a
commutative ring, I an ideal in R and A an R-module. We always have
0 ⊆{a ∈ A|(1 − i)a = 0∃i ∈ I}⊆ I⋂n=1∞InA ⊆⋂n=1∞InA. In this paper we
investigate conditions under which certain of these containments may or may not be
replaced by equality.