Carbon dioxide (CO₂) as a gas — select the correct set of properties relevant to fire and safety considerations.

Introduction / Context:
Basic gas properties are essential in refrigeration, fire suppression, and safety engineering. CO₂ is widely used as a fire extinguishing agent and as a refrigerant in transcritical systems.

Given Data / Assumptions:

• CO₂ at ordinary conditions (non-cryogenic).
• Properties considered: colour, odour, and flammability.

Concept / Approach:
CO₂ is colourless and odourless. It does not support combustion and is used to smother fires by diluting oxygen concentration. While CO₂ is asphyxiant at high concentrations, it is not classified as a flammable gas.

Step-by-Step Solution:

Verification / Alternative check:
Fire codes and data sheets list CO₂ as non-flammable and suitable for certain classes of fires, confirming these properties.

Why Other Options Are Wrong:

Picking any single property ignores the others; “toxic and highly flammable” is incorrect.

Common Pitfalls:
Confusing CO₂ with CO (carbon monoxide). CO is toxic; CO₂ is an asphyxiant at high concentrations but not flammable.

Final Answer:

all of these