The Cotton Fire Challenge – Field-cotton is one of the most flammable materials ever tested by the US government. Even minor abrasion can result in ignition. In addition, cotton is extremely hydrophobic (i.e. it actively repels water) which significantly reduces the effectiveness of regular water as an extinguishing agent. Lastly, cotton is prone to smoldering which, when combined with its hydrophobic nature, makes it considerably more difficult to penetrate and extinguish. These characteristics then lead to to a very high risk of re-ignition.