In the 1980s, I was employed by a security firm where I installed and maintained surveillance cameras in almost 100 locations, mainly banks. I had between 250-300 of these cameras that took 100 foot rolls of 35mm film. We bought 100 Ft. Tri-X by the case! Until my employment, the company had film processed by a local lab that had one of the machines mentioned in posts above. I talked the company into building me a darkroom to save money. While I would have preferred to have the large reels that would hold 100 ft., that seemed too expensive, and less than practical for our needs, and I used the method that ic-racer described. I would use 8 standard 35mm reels in a 13" (IIRC) tank.
Originally Posted by ic-racer
This actually worked out pretty well, as the cameras were operated intermittently by the tellers, taking a few frames at a time; unless the alarm was tripped, which ran the camera until the alarm was reset or (more usually) it ran out of film. In either case, working backward from the end of the exposed part of the roll got me the picture of the actor in question. Even with a robbery, I rarely had to go back past the last 20-25 ft. I would get on the first 8 reels.