Cleaning of a proportioner pump after contamination with a fluorinated foam agent.

Following our article 'Changing a FireDos proportioner over to fluorine-free foam agents' of 12 July 2021, we had the pump of an FD10000/1 proportioner cleaned using the PerfluorAd method after contamination with a fluorinated foam agent.

The system is a standard application with no special exposure. The pump has been filled with a 1% AFFF foam agent since 2015.

• The foam agent was removed from the pump.
• The pump was flushed with water.
• A zero sample was taken from the flushing water.

Generally, the AFFF agents of newer production have PFAS analyzable as individual substances merely as side products now. It is becoming more common to use so-called capstone products (other polyfluorinated substances) that can be detected only via the definition of "organically bonded fluorine" (while not being able to identify the individual PFAS molecular structure). These capstone products are considered in the analysis.

The total amount of PFAS was reduced from 137,718 µg/l (ppb) in the zero sample to 0.44 µg/l in the final sample (the drinking water limiting value is 0.5 µg/l, the limiting value in foam agent concentrates is 1,000 µg/l).

There is currently no clear guideline by the authorities about where the limiting value after cleaning should be. FireDos has set its limiting value of < 1.0 µg/l total PFAS after cleaning, without this benchmark figure being legally binding. Although it is always aimed at a 'zero', this cannot be achieved in all projects. When using a fluorine-free foam agent at a proportioning rate of 1%, the extinguishing water is contaminated with 0.0044 µg/l at a residual PFAS exposure of 0.44 µg/l (ppb). This value is far below the limiting value for drinking water.