How the smell from a leaking gas tap quickly fills the whole room?

When a gas tap is leaking, the gas, often mixed with a sulfur-like odorant for safety, quickly diffuses into the air due to its low molecular weight. The gas molecules disperse rapidly, filling the room as they seek to equalize concentration levels. Since gas is lighter than air, it tends to rise and spread across the space, making the smell noticeable almost immediately. Proper ventilation is crucial, as it helps dilute the gas and mitigate potential hazards.