Does Antiformin 'S' go off?

[OvenHiker]

I have some Brupaks Antiformin S 'beer line cleaner' that is taking a while to get through. I've just mixed up a new bottle full and noticed there isn't the chlorine smell I've come to expect. The neat bottle too has lost the strong chlorine. So, does this stuff go off?

[OvenHiker]

To answer my own query, it appears that Murphy's say that it does lose chlorine over time, even at recommended storage temps.