The most significant way in which food processing machinery differs from other general industrial machinery is that it is required to meet requirements in terms of hygiene along with requirements related to safety for workers. When considering aspects of safety, it is necessary for a movable guard to be installed on product contact surfaces that workers frequently access so as to satisfy safety requirements. When installing a movable guard on product contact surface, it is crucial to strictly consider not only aspects related to safety but also relevant requirements related to hygiene. However, design methods with respect to the structure of movable guards that consider aspects related to hygiene are not found within ISO standards related to machinery safety. This paper focuses on a position detector for interlocking guards generally used as movable guards. This paper logically clarifies the following: (1) issues with respect to hygiene when using position detectors, (2) Conditions for safety and hygiene that designers should consider, and (3) key points that a designers should consider when selecting position detectors.