This type of headlight that uses a trace of bromine or iodine vapor is the standard in auto manufacture
[DOC] [TLE] Basic Physics of the Incandescent Lamp (Lightbulb) - Moodle [PAR] and nonhazardous to manufacture, although less energy ... nologies.1 The 
mercury vapor fluorescent ... about 2900 K in standard incandescent bulbs, .... 
traces of a halogen gas such as bromine or iodine.