text: Oil reservoirs are routinely mapped by injecting a PFT down one bore hole and measuring the concentration at adjacent boreholes. In this way, geologists can build up an image of the reservoir.
  Traditional underground high-tension cables are constructed either with internal oil ducts or channels or by the use of a pipe through which the insulated conductor is installed. In either design the system is then filled with pressurised, de-gassed oil. The oils primary function is to improve the insulating properties of the cable but occasionally leaks can occur through cable joints, oil system fittings or cable sheath damage. The leak is initially identified by the loss of liquid from the system, but its location used to involve engineers digging up the road, freezing a section of cable and seeing if the level was still going down, then choosing a new point to dig and re-freeze. It could take several holes to isolate the leak. If a PFT is injected into the oil, there will be a relatively high concentration of PFT above the leak, which can be pin-pointed to within a few feet, requiring only a single hole to be dug right where the leak is.
  PFTs have been used to follow air movement, for tracing the flow of pollutants, for example, the Big Bend Regional Aerosol and Visibility Observational study. measuring the effectiveness of ventilation and studying the possible effects of terrorist attacks (for example in New York ).
  PFTs have even been used to track ransom money after a kidnapping.