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

Gases are primarily classified by how they affect the human body: poison gas

: Deprive the body of oxygen. Chemical asphyxiants (e.g., carbon monoxide) interfere with oxygen transport in the blood, while simple asphyxiants (e.g., nitrogen or argon) displace breathable oxygen in confined spaces. Poison gas was first used on a large

Smells like "moldy hay"; effects can be delayed for 48 hours Historical Use in Warfare while simple asphyxiants (e.g.