Passive RFID tags are maintenance-free and generally robustly built. Problems most typically arise in the form of poor readability from a longer distance. Additionally, environmental factors like metal or water located near the tag can cause difficulty in the tag being read. Read the Adhesive Tag Fixation: How to Bond RFID Tags white paper for tips & tricks on how to best mount an RFID tag.
 

(1):     Metal: Most RFID tags experience reduced performance when used near metal. A tag placed directly on a metal surface will likely not read at all.

        There are RFID tags that have been specifically designed for use on or near metal. These tags typically have a special housing which provides a gap of controlled thickness between the tag antenna and the metal surface or have a built-in metal foil and are tuned to optimized performance near metal.

(2):   Proximity: RFID tags placed too closely can interfere with each other. This is especially true for UHF tags. There are minimum spacing guidelines for each type of tag that must be followed to ensure proper functioning.

(3):     Water and moisture: The majority of tags are physically unaffected by water, however, the read range of some tags diminishes significantly in the presence of moisture. As a rule, the higher the frequency, the more likely the read-range will be impacted by moisture. While LF read range is essentially unaffected by water, UHF read range is strongly reduced while the tag is wet.

(4):     Fixation: There are multiple ways to affix tags to surfaces, and it is important to choose the right method for the application. It is important to ensure maximum contact between the tag and the surface. This is especially important for adhesive fixation. Maximum contact will help to ensure that the tag remains in place when exposed to mechanical shock and vibration.