Refrigerant Gas R404A is a colorless odorless mixture of three hydrofluorocarbon compounds in near-azeotropic proportions. Azeotropic mixtures have sharp boiling points instead of boiling over a range of temperatures, which is the case with most mixtures. Bp (at 1 atm) -46.5°C.Density (as a liquid) 0.485 kg/L. Shipped as a liquid under its own vapor pressure. The vapors are heavier than air and can cause asphyxiation by the displacement of air. Contact with the liquid can cause frostbite. Prolonged exposure to fire or intense heat may cause the containers to rupture violently and rocket.