Which of the following lamps contains a poisonous gas and therefore should be. disposed safely ?

Compact Fluorescent Lamps (CFLs) contain mercury, a highly toxic heavy metal that exists as a liquid or vapor within the sealed glass tube [2]. Mercury is essential for the lamp's operation, as it absorbs ultraviolet light to emit visible light. However, mercury is a potent neurotoxin that can cause fatal poisoning, damage kidneys, and harm fetal development [2]. Because mercury can easily evaporate into a colorless, odorless vapor if the bulb breaks, CFLs are classified as hazardous waste and must be disposed of or recycled safely to prevent environmental contamination of groundwater and soil [1]. In contrast, Light Emitting Diodes (LEDs) are generally considered more environmentally friendly and do not contain mercury [2]. Halogen lamps use halogen gas similar to incandescent bulbs, and neon lamps use inert noble gases, neither of which pose the same level of toxic risk as mercury-containing CFLs.

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > 29.r.4. Mercury > p. 413
2. [2] https://www.osha.gov/sites/default/files/publications/mercuryexposure_fluorescentbulbs_factsheet.pdf