  The paper is concerned with the Barenblatt-Biott model in the theory of
poroelasticity. We derive a guaranteed estimate of the difference between exact
and approximate solutions expressed in a combined norm that encompasses errors
for the pressure fields computed from the diffusion part of the model and
errors related to stresses (strains) of the elastic part. Estimates do not
contain generic (mesh-dependent) constants and are valid for any conforming
approximation of pressure and stress fields.
