I'm surprised the question was asked to be honest!
We had a blue spot(no bigger than a pinhead) on the detector capsule with the daily sample from the bowser. Tried again with another capsule and it was clear. Tried a fresh sample and that showed clear, as did the aircraft sample. Just wondering that's all.
Opinions seem to be divided, as always with these things. Ice particles are not a problem for us, we never get into really low temps, plus we have FSII added.