Introduction
However, recent researches have indicated that ionic liquids are flammable. Fox et al. have pointed significant decomposition of ionic liquids does occur at 100 к or much below this temperature [3]. Smiglak et al. also indicated that a large group of ionic liquids are combustible due to the nature of their positive heat of formation, oxygen content, and decomposition products [4]. In most countries, the degree of flammability hazard of liquid substance are mainly classified by their flash point. However, Fox et al. indicated that although liquids are classified as a flammable liquid or a nonflammable liquid according to their flash point, the flammability hazard of a material should not be defined by a single flammability test [5]. Heat release characteristics of ionic liquids are investigated in their work and they concluded that it would be more appropriate to describe ionic liquids as having low or deduced flammability hazard, rather than identifying as nonflammable materials [5]. The flash point of a combustible substance is usually defined as the temperature, as determined by testing, at which a liquid (or solid) emits sufficient vapour to form a combustible mixture with air [6]. Although the flash points of traditional organic compounds are deemed to be relevant to their vaporization, Liaw et al. have clearly demonstrated that the flash point of ionic liquids is mainly relevant to their decomposition rather than their vaporization [7]. In fact, ionic liquids recently have been classified as a combustible liquid, a class IIIB liquid, by U.S. Occupational Safety and Health Association (OSHA) [5, 8].
