Final answer:
Mobile, portable, and fixed fill stations are all designed to refill SCBA at emergency incidents. Each serves a different operational capacity with mobile and portable units being specifically designed for use at the scene of an emergency.
Step-by-step explanation:
The type of fill station designed to refill Self-Contained Breathing Apparatus (SCBA) at emergency incidents is a mobile fill station. This type of station is integral for emergency response as it can be transported to the site of the incident, where firefighters or rescue personnel can quickly refill their SCBA tanks, allowing them to continue operations without having to return to a fixed, potentially distant, location. Portable fill stations are also used, especially in smaller-scale or remote operations, for their ease of relocation.
Although fixed fill stations exist, they are typically installed at fire stations or training centers rather than at the scene of an emergency. Therefore, the correct answer is 4) All of the above, as both mobile and portable fill stations can be used at the scene, in addition to fixed stations that can serve in certain emergency circumstances.