Fire extinguisher had been developed by DuPont and the US Army in 1954. Both 1211 and 1301 work by inhibiting the chain reaction of the fire, and in the case of Halon 1211, cooling class A fuels as well. Halon is still in use today but is falling out of favor for many uses due to its environmental impact. Europe and Australia have severely restricted its use, since the Montreal Protocol of 1987. Less severe restrictions have been implemented in the United States, the Middle East, and Asia. Internationally there are several accepted classification methods for hand-held fire extinguisher. Each classification is
Gas in a box gas can no longer be considered to be a Maxwell–Boltzmann gas. where "Λ" is now the thermal wavelength for massless particles. The following sections give an example of results for some specific cases. For this case: Integrating the energy distribution function and solving for "N" gives Substituting into the original energy distribution function gives which are the same results obtained classically for the Maxwell–Boltzmann distribution. Further results can be found in the classical section of the article on the ideal gas. For this case: Integrating the energy distribution function and solving for "N" gives the particle number where Li("z") is