Mechanical measurements of work of breathing, respiratory pressures and hydrostatic imbalance were carried out on five different types of rebreathers for mine clearance diving, on the surface and at maximum diving depth for each machine. The diving systems were tested according to the methods described in the European Standard for closed and semi-closed rebreathers. The oxygen partial pressures in the diving apparatuses were also tested during simulated respiration using FOI's metabolic simulator. These tests were also carried out at surface and at the by the manufacturer described maximum diving depth. The results showed that none of these systems passed all the limits for breathing resistance and hydrostatic imbalance that have been set by the European Committee for Standardization. The oxygen partial pressures remained within safe limits at the designed depths.