Most SurvivalBlog readers are probably familiar with the rule of threes: You can survive 3 minutes without breathable air or in icy water before losing consciousness. You can survive 3 hours without adequate shelter/clothing in conditions of extreme heat and (especially) cold. You can survive 3 days without water. Drinking unpotable water may extend your survival somewhat, but you may ultimately succumb to illness due to waterborne pathogens or toxins. You can survive 3 weeks without food. This rule outlines your priorities in a survival situation. If you fall through the ice into a frozen lake, obtaining an adequate supply … The post Travel Berkey Water Filter, by Thomas Christianson appeared first on SurvivalBlog.com.