Since I am running around NYC alot, my PSK is geared toward an urban calamity. I carry one bottle (50) iodine tabs, but they are to be used two tabs per litre. I also carry 4-6 plastic bags.

My concern is that if there is a problem in NYC, the contamination is just as likely to be chemical rather than biological. Carrying a Katydyne (sp?) capable of filtering chemicals would make the kit bulky. Still working on that one.