In this paper two exact
sequences are established which are useful in computing π0𝒞(M), the group of
isotopy classes of concordances for a noncompact Hilbert cube manifold M. Roughly
speaking, this enables one to study the noncompact case in terms of the compact
case. The situation is analogous to Siebenmann’s description of groups of infinite
simple homotopy types in terms of two exact sequences.