A head mount device, HMD, configured to be worn on a human body, comprising: a housing comprising: a first plate; a second plate facing a direction opposite a direction of the first plate; and a sidewall (113, 1131, 1132, 1133, 1134) surrounding a first space (1101, 1102) between the first plate and the second plate, the first space (1101, 1102) being a sealed space; and at least one electronic or optical component (121, 122, 130) disposed in the first space (1101, 1102) of the housing, wherein at least a part of the sidewall (113, 1131, 1132, 1133, 1134) of the housing comprises a moisture induction portion configured to induce moisture in the first space (1101, 1102) to be generated in a moisture induction region including the moisture induction portion of the sidewall (113, 1131, 1132, 1133, 1134); wherein the moisture induction region of the moisture induction portion of the sidewall (113, 1131, 1132, 1133, 1134) comprises a recess formed in the sidewall (113, 1131, 1132, 1133, 1134) having a thickness that is less than a thickness of a periphery of the sidewall (113, 1131, 1132, 1133, 1134); and wherein the HMD moreover comprises: an external housing arranged to surround at least a part of the housing, a second space formed between the external housing and the housing; and at least one vent (115, 154, 155) formed on a part of the housing and/or the external housing, the at least one vent (115, 154, 155) configured to allow external air to flow into the second space. a housing comprising: a first plate; a second plate facing a direction opposite a direction of the first plate; and a sidewall (113, 1131, 1132, 1133, 1134) surrounding a first space (1101, 1102) between the first plate and the second plate, the first space (1101, 1102) being a sealed space; and at least one electronic or optical component (121, 122, 130) disposed in the first space (1101, 1102) of the housing, wherein at least a part of the sidewall (113, 1131, 1132, 1133, 1134) of the housing comprises a moisture induction portion configured to induce moisture in the first space (1101, 1102) to be generated in a moisture induction region including the moisture induction portion of the sidewall (113, 1131, 1132, 1133, 1134); wherein the moisture induction region of the moisture induction portion of the sidewall (113, 1131, 1132, 1133, 1134) comprises a recess formed in the sidewall (113, 1131, 1132, 1133, 1134) having a thickness that is less than a thickness of a periphery of the sidewall (113, 1131, 1132, 1133, 1134); and wherein the HMD moreover comprises: an external housing arranged to surround at least a part of the housing, a second space formed between the external housing and the housing; and at least one vent (115, 154, 155) formed on a part of the housing and/or the external housing, the at least one vent (115, 154, 155) configured to allow external air to flow into the second space. an external housing arranged to surround at least a part of the housing, a second space formed between the external housing and the housing; and at least one vent (115, 154, 155) formed on a part of the housing and/or the external housing, the at least one vent (115, 154, 155) configured to allow external air to flow into the second space.