The option to boil water was added in the 184.108.40.206 update of DayZ. In the event of receiving a disease from blood bags, eating raw meat, drop in body temperature, and taking too many hits from zombies, you can also get infected by drinking non-boiled water. Though this is only chance, it does not eliminate the possibility of becoming sick. In order to do so, you will need to boil the water you have stored in your canteen. For this, you will need:
|Box of Matches||1|
|Empty Tin Can||1|
To begin, you will need to make a Mod:Fireplace using your Box of Matches, and a Mod:Wood Pile you obtain by harvesting wood from a tree inside of a forest. With the Wood Pile in your inventory, right click on your Box of Matches and select the option, "Create a Fireplace".
Wood Piles take up 1 inventory slot.
After successfully lighting your Fireplace, in the interactions menu, you will see an option to "boil water". You must have the Empty Tin Can and the Canteen in your inventory in order to boil the water. The Empty Tin Can is not consumed in the process of boiling.
NOTE: Alternative fire sources include burning tires/oil cans.