I finally caught up and watched the TV programme on the Queen, the 3 parter and one thing struck me, they showed them doing a deck decontam for Nuclear fallout where sprays flood the deck to wash off any contamination. later on they did the same using the system to spray foam in case of a deck fire, they then swept the stuff overboard as it is corrosive and not good for the carrier, I sat there thinking, why on earth do you just not select water again and wash it off instead of spending hours with brushes trying to remove it, it would also flush the pipes..