USA: A long-banned CFC has mysteriously turned up in air quality monitoring tests carried out during a natural gas well fire in Pennsylvania.

Officers from the Pennsylvania Department of Environmental Protection conducting ambient air quality tests at the well pad in Greene County in February detected quantities of dichlorotetrafluoroethane, a CFC previously used in chillers as R114 or as the fire suppressant Halon 242.

Samples collected during the event were analysed for 57 toxic air pollutants. None were detected at dangerous concentrations and some, including the hydrocarbons propene, heptane and trimethylbenzene, were likely to have been directly associated with the fire.

However, the detection of dichlorotetrafluoroethane in more than half the study samples was unexpected as it is rarely detected at other sites.

According to the Pennsylvania Department of Environmental Protection report, the possibility exists that the R114 may have been used by emergency responders to fight and contain the fire or had been contained on some on-site cooling or fire-suppression apparatus. Its use by the military and for “essential uses” is still allowable.