The invention provides a coil apparatus (100) for inductive power transmission, comprising an electromagnetic coil (102) for emitting and/or picking up an electromagnetic field (112) on a transmission side (106) of the coil apparatus (100), and comprising a housing wall (104), which covers the coil (102) on the transmission side (106) and is transmissive to the electromagnetic field (112). Furthermore, the coil apparatus (100) comprises a housing medium (108), which is enclosed by the housing wall (104) in such a way that, when a through-opening (110) is formed in the housing wall (104), the housing medium (108) passes through the through-opening (110). Alternatively, a housing vacuum is provided which is enclosed by the housing wall in such a way that, when a through-opening is formed in the housing wall, atmospheric air (118) passes through the through-opening. Among further aspects, a vehicle comprising such a coil apparatus and a method for inductive power transmission are provided. The method comprises steps of providing an electromagnetic coil (102) for emitting and/or picking up an electromagnetic field (112), covering the coil (102) on a transmission side (106) with a housing wall (104) which is transmissive to the electromagnetic field (112), enclosing a fluid (116) with an internal pressure which is different than the atmospheric air by the housing wall (104), sending the internal pressure, evaluating whether the internal pressure reaches a presettable internal pressure threshold value, and outputting a signal when the internal pressure reaches the internal pressure threshold value.