Nerve agent and Poison gas

Nerve agent noun - A toxic gas that is inhaled or absorbed through the skin and has harmful effects on the nervous and respiratory system.

Poison gas and nerve agent are semantically related. In some cases you can use "Poison gas" instead a noun phrase "Nerve agent".

Poison gas noun - A gas that is poisonous to breath or contact; used in chemical warfare.

Nerve agent and poison gas are semantically related. Sometimes you can replace phrase "Nerve agent" with "Poison gas", this phrases are similar.