Housing module of a field device used in measuring and automation engineering, comprising: a housing with a housing wall (11.1) and a first housing chamber (12.1) and a second housing chamber (12.2), wherein the housing chambers are separated by a detachable partition wall, wherein a measuring/operating electronics unit (19.1) of the field device is arranged in the first housing chamber, and wherein a connection electronics unit (19.2) to connect cables for the supply of power to the field device and/or for the exchange of data is arranged in the second housing chamber, wherein, on an inside (11.11), the housing wall has a first wall section (11.21) designed to receive the partition wall, wherein the first wall section is separated from a lateral surface (13.5) of the partition wall by a gap surrounding the partition wall, wherein the gap has a path length on a plane containing a longitudinal section of the partition wall, wherein a ratio of the gap width to the path length is less than 0.05, and particularly less than 0.025 and preferably less than 0.02 and meets the EX-d standard according to IEC60079-1 of 2014-06, EN60079-1 of 2014-06, wherein a safety apparatus is provided to limit the leeway the partition wall has to move in the direction of the second housing chamber, characterized in that the housing wall has a second wall section (11.22) on the inside wherein, in the second housing section, the housing wall has at least a groove (11.3) at least in sections, wherein the groove runs parallel to a cross-sectional plane of the transition wall, wherein the safety apparatus has an engagement unit (14.1) which is designed to engage in the groove, wherein the engagement unit has at least two engagement elements (14.2) wherein the engagement elements are guided into an associated groove, going from a starting position (16.1) to a target position (16.2) when the safety apparatus is mounted in the second housing chamber, wherein the engagement elements can be fixed in the target position by a fastening apparatus. a housing with a housing wall (11.1) and a first housing chamber (12.1) and a second housing chamber (12.2), wherein the housing chambers are separated by a detachable partition wall, wherein a measuring/operating electronics unit (19.1) of the field device is arranged in the first housing chamber, and wherein a connection electronics unit (19.2) to connect cables for the supply of power to the field device and/or for the exchange of data is arranged in the second housing chamber, wherein, on an inside (11.11), the housing wall has a first wall section (11.21) designed to receive the partition wall, wherein the first wall section is separated from a lateral surface (13.5) of the partition wall by a gap surrounding the partition wall, wherein the gap has a path length on a plane containing a longitudinal section of the partition wall, wherein a ratio of the gap width to the path length is less than 0.05, and particularly less than 0.025 and preferably less than 0.02 and meets the EX-d standard according to IEC60079-1 of 2014-06, EN60079-1 of 2014-06, wherein a safety apparatus is provided to limit the leeway the partition wall has to move in the direction of the second housing chamber, characterized in that the housing wall has a second wall section (11.22) on the inside wherein, in the second housing section, the housing wall has at least a groove (11.3) at least in sections, wherein the groove runs parallel to a cross-sectional plane of the transition wall, wherein the safety apparatus has an engagement unit (14.1) which is designed to engage in the groove, wherein the engagement unit has at least two engagement elements (14.2) wherein the engagement elements are guided into an associated groove, going from a starting position (16.1) to a target position (16.2) when the safety apparatus is mounted in the second housing chamber, wherein the engagement elements can be fixed in the target position by a fastening apparatus.