This work presents an extension to the traditional FMECA (Failure Modes, Effects and Criticality Analysis) method to include the effects of human factors concerning accessibility/repairability, probability of contact and degree of contact. The authors refer to this extension to the traditional FMECA as the Human Design Approach (HDA). All data used in this study was collected during the stay of two of the authors at the Mars Desert Research Station (MDRS) in the Utah desert, USA. The MDRS is a laboratory for carrying out research in order to understand and investigate the difficulties of how to live and work on another planet. The results show that following the HDA can enhance the safety and reliability of the MDRS. There is still a significant amount of research required concerning reliability analysis of the space habitat in terms of the selection of optimum designs, the modification of systems, as well as access, inspection and maintenance strategies, human factors and environmental impacts. This preliminary study will assist the design engineers with the selection of an optimum configuration for space habitats and can be extended to any case where humans can influence function of an environment.