Difluoromethane, also called difluoromethylene, HFC-32 Methylene Fluoride or R-32, is an organic compound of the dihalogenoalkane variety. It has the formula of CH2F2. It is a colorless gas in the ambient atmosphere and is slightly soluble in the water, with a high thermal stability. Due to the low melting and boiling point, (-136.0 °C and -51.6 °C respectively) contact with this compound may result in frostbite. In the United States, the Clean Air Act Section 111 on Volatile Organic Compounds (VOC) has listed difluoromethane as an exception (since 1997) from the definition of VOC due to its low production of tropospheric ozone. Difluoromethane is commonly used in endothermic processes such as refrigeration or air conditioning. Synthesis Difluoromethane is primarily synthesized via batch processes, by the reaction of dichloromethane and hydrogen fluoride (HF), in the liquid phase using SbCl5 as a catalyst. Due to hydrogen fluoride's hazardous properties, a new synthesis was developed. The new synthesis allows for constant flow of difluoromethane production through an isolated chamber. Applications Difluoromethane is often used as a fire extinguishant due to its ability to undergo endothermic processes. Atmospheric concentration of difluoromethane at various latitudes since the year 2009 are shown to the left. Difluoromethane is a molecule used as refrigerant that has prominent heat transfer and pressure drop performance, both in condensation and vaporization. It has a 100-year global warming potential (GWP) of 675 times that of carbon dioxide, and an atmospheric lifetime of nearly 5 years. It is classified as A2L - slightly flammable by ASHRAE, and has zero ozone depletion potential (ODP). Difluoromethane is thus a relatively low-risk choice among HFC refrigerants, most of which have higher GWP and longer persistence when leaks occur. The common refrigerant R-410A is a zeotropic, 50/50-mass-percent mixture of difluoromethane and pentafluoroethane (R-125). Pentafluoroethane is a common replacement for various chlorofluorocarbons (i.e Freon) in new refrigerant systems, especially for air-conditioning. The zeotropic mix of difluoromethane with pentafluoroethane (R-125) and tetrafluoroethane (R-134a) is known as R-407A through R-407F depending on the composition. Likewise, R-504 is the azeotropic (48.2/51.8 mass%) mixture of difluoromethane and chlorotrifluoromethane (R13). In 2011 17,949,893 metric tons of difluoromethane were emitted into the atmosphere in the United States alone. Difluoromethane is currently used by itself in residential and commercial air-conditioners in Japan, China, and India as a substitute for R-410A. In order to reduce the residual risk associated with its mild flammability, this molecule should