Halomethane compounds are derivatives of methane with one or more of the hydrogen atoms replaced with halogen atoms. Halomethanes are both naturally occurring, especially in marine environments, and human-made, most notably as refrigerants, solvents, propellants, and fumigants. Many, including the chlorofluorocarbons, have attracted wide attention because they become active when exposed to ultraviolet light found at high altitudes and destroy the Earth's protective ozone layer.
Halon-based fire extinguishing system inside Diefenbunker, a nuclear fallout bunker in Canada.
Halon-based hand-held fire extinguishers
Bromine is a chemical element; it has symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between those of chlorine and iodine. Isolated independently by two chemists, Carl Jacob Löwig and Antoine Jérôme Balard, its name was derived from the Ancient Greek βρῶμος (bromos) meaning "stench", referring to its sharp and pungent smell.
Liquid and gas bromine inside transparent cube
Antoine Balard, one of the discoverers of bromine
View of salt evaporation pans on the Dead Sea, where Jordan (right) and Israel (left) produce salt and bromine
Baltimore's Emerson Bromo-Seltzer Tower, originally part of the headquarters of Emerson Drug Company, which made Bromo-Seltzer