The LHCb calorimeter system comprises a preshower detector, an electromagnetic and a hadronic calorimeter. The purpose of the calorimeters is to identify and provide an energy and position measurement of photons, electrons and hadrons. The calorimeters are an essential part of the LHCb trigger, and are used in offline analysis. Good photon identification is important for the study of B decays with π 0 s in the final state, an example of which is the B d 0 → π + π − π 0 decay. This provides an alternative channel to B d 0 → π + π − for the measurement of the angle α of the unitarity triangle.