OCR Text |
Show The Controlling Factor in Forest Fire Hazard Is Undoubtedly Humidity By C. E. NORQUEST, U. S. Weather Bureau. The element that seems to claim the distinction of being the controlling con-trolling factor in forest fire hazard is undoubtedly humidity. As it fluctuates the degree of fire hazard increases and decreases. Temperature Tempera-ture and wind only accentuate the influence of low humidity. It makes no difference how hot the day or how high the wind, if the forest materials ma-terials are wet fire will neither shirt nor spread. The seeming exception excep-tion to this general assertion is the lightning fire that may be started even in the rain. All dead forest materials are hygroscopic, some to a very high degree, and readily absorb moisture from humid air or lose it to dry air, so that to a marked degree the moisture content, and hence the inflammability, of forest materials is determined by the humidity of the air to which they are exposed. There is no fire hazard before the moisture content of forest materials has dropped to the inflammability point and the degree of hazard increases rapidly with further drying, which is accelerated by rising temperature and wind. |