Something that alot of Preppers dont think about but should have in their arsenal even more so if you live close to water and mountains. RE BREATHERS are not hard to find but can be pricey and most well stocked SCUBA and MILITARY surplus stores do carry. Very Important if you are in a scenario close to water and need to stay in for awhile. O2 is very good to have in your pack even if its just a small five minute bottle. Stress and anxiety on the body can cause premature burnout even for the most fit PREPPER.A good shot of O2 in your pack is vital for doing cross country trecks where any elevation that you have not been exposed to comes apparent. Elevation sickness can occur even at heights below 6000ft for better aged adults and young children. VITAMIN E has been known to aid and prevent high altitude sickness but must be taken at least 3 weeks prior to hikes and in high doses. The small o2 tanks will fit nicely in the PVC six pack. The REBREATHERS or DRAEGER GEAR can be found at better Surplus stores in the USA.