Gas — Poison

: Absorbed into the bloodstream to damage specific organs or cellular respiration. Hydrogen cyanide is a potent systemic toxin. Common Toxic Gases and Sources Common Sources Key Characteristics Carbon Monoxide (CO) Incomplete combustion (engines, heaters) Colorless, odorless, "silent killer" Hydrogen Sulfide (H₂S) Manure decomposition, sewers, oil refining "Rotten egg" smell; paralyzes sense of smell at high levels Chlorine (Cl₂) Water treatment, industrial manufacturing Greenish-yellow; pungent bleach-like odor Ammonia (NH₃) Fertilizers, industrial refrigeration Sharp, pungent odor; severe respiratory irritant Phosgene (COCl₂) Plastics and pesticide production

Smells like "moldy hay"; effects can be delayed for 48 hours Historical Use in Warfare poison gas

Poison gas was first used on a large scale during World War I to break trench stalemates. First Usage of Poison Gas - National WWI Museum : Absorbed into the bloodstream to damage specific