The gas used in fire extinguisher:

The correct answer is Carbon dioxide.

Key Points

• Carbon dioxide (CO₂) is widely used in fire extinguishers due to its non-combustible properties.
• It works by displacing oxygen in the surroundings, which is essential for combustion, thereby stopping the fire.
• CO₂ fire extinguishers are ideal for electrical fires because CO₂ is non-conductive.
• It leaves no residue after extinguishing a fire, making it suitable for sensitive equipment like computers and electronics.

Additional Information

• Nitrogen oxide: Nitrogen oxides (NOx) are gases produced from combustion processes and are known for their environmental impact, such as contributing to smog and acid rain. 
• Carbon monoxide: Carbon monoxide (CO) is a toxic gas formed by incomplete combustion. 
• Sulphur dioxide: Sulphur dioxide (SO₂) is a toxic gas with a pungent odor, primarily released by volcanic activity and industrial processes. 
• Other gases: While other gases like halon and inert gases are used in specialized fire suppression systems, none of them are as commonly used in portable fire extinguishers as Carbon dioxide.