## 1 Introduction  
Complex organizations of building spaces usually create maintenance difficulties due to the design of mechanical, electrical, and plumbing (MEP) systems. This complexity not only necessitates expertise to fully comprehend design drawings, but also specialized knowledge to document and maintain a diversity of mechanical components and equipment. Since building spaces feature different levels and layouts with the incorporation of various parts, intensive design efforts are required to make optimal use of the limited space available for both the building systems and its occupants. The relationship between the original design information and its orientation in real spaces is frequently imperfect. Thus, it can be difficult to identify a perfect way to confirm the relative location of pipes that originate from the other side of a wall. The integration of building component information and on-site maintenance is critical for as-built facility management (FM). In reality, accurately determining the locations of building components is characterized by difficulty and ambiguity. Since building design data are not updated frequently, using original design drawings to troubleshoot on-site situations becomes very challenging, especially when the specific maintenance work necessitates additional effort or experience. For monitoring or inspection after a building is occupied, a thorough comprehension of the corresponding operational manual is usually required, as is a well-controlled operational procedure in combination with hands-onexperience in a real site. Although 3D models and attributes defined in building information modeling (BIM) contribute to complete facility information, which can be accessed by maintenance workers from cloud computing services, in reality, the connectivity of piping layouts and the exact points of penetration are very difficult to follow from one space to another and beyond partitions. This difficulty can be increased when inspections have to be made across systems, where different levels of accuracy and symbolic representations exist. Allocation of maintenance space, which constitutes an important safety concern, should be planned in advance and clearly indicated in building design diagrams afterward. Due to the complicated layout of mechanical equipment and the limited availability of nearby free space, space to access pipes may not be sufficiently large. In order to prevent unexpected injury, a route with clear signage and free of unanticipated obstacles should be provided with an appropriate visibility related to the updated location of the maintenance space. A methodological approach to test BIM modelling needs to be applied from an empirical experiment of system design, test, and evaluation. Augmented reality (AR), using piping geometries facilitated by and integrated with both information and reality, can project BIM models into an environment for maintenance workers to follow. An AR system is needed to illustrate the application and integration potential of BIM in facility management, considering the co-relation problems between different systems and their operations in a real as-built environment. A cooling tower and piping maintenance case that applies simultaneous localization and mapping (SLAM) technology in positioning should also be investigated in order to support BIM-based AR maintenance troubleshooting. A smartphone-based system, which is convenient, should be investigated to provide functions that support the operating system under different lighting conditions, indicate safe maintenance routes, and show 3D-animated operational procedures. A Post-Study System Usability Questionnaire (PSSUQ) test should also be conducted with a number of users for statistical feedback on utilizing the BIM-based AR system to quickly locate inter-related components, such as pipes, cooling towers, and power switches. If the above-mentioned objectives are achieved and tested, maintenance efficiency and safety should be increased. The article is organized as follows:  
1. Introduction;
2.