Fuel cell unit

The device has a housing, a substrate (121) and an electrode (122) on an electrode side (226) of the substrate. The substrate is designed to enable gas to pass from a gas chamber (124) on a gas chamber side of the substrate to the electrode. The substrate has at least one essentially gas-tight zone (224) that extends from one surface of the substrate through to the opposite surface of the substrate. AN Independent claim is also included for the following: a block of fuel cell units.