Which gas is commonly known as laughing gas?

1. Carbon dioxide
2. Oxygen
3. Nitrous oxide
4. Helium

Nitrous oxide (N₂O), or laughing gas, induces euphoria and analgesia when inhaled. Medically, it’s used as an anesthetic. Environmentally, it’s a potent greenhouse gas and ozone-depleting substance, emitted from agriculture and combustion.