Surveillance IR photography is used for surveillance. The most important concept to understand is that IR film does not see at night or in the dark. An IR light source is needed to get the shot needed. What makes IR film useful in this application is that an IR light source cannot be scene by the human eye. Here is an example of how you would use this film in a surveillance application.
Lets say there is a meeting prearrange in a place, an alley.
You would then set up IR light sources to flood the area with IR light. It can't be scene by the human eye, so someone hidden could photograph the meeting. An easy way to do this would be to block out the inside of a window with IR passing filters. Then behind the window inside the building, a couple of high wattage lights would be place to shine outside. The ally would still appear dark.