LPG is a mixture of gases, mainly propane and butane. These gases are odorless, which means they don't have a smell on their own. However, for safety reasons, a chemical called mercaptan is added to LPG before it's distributed to give it a distinct smell – often described as rotten eggs or sulfur-like.
Now, when an LPG cylinder is about to run out of gas, the pressure inside decreases. As the pressure drops, the gas molecules become less dense, allowing more of the odorant (mercaptan) to escape from the remaining gas in the cylinder. This increased concentration of mercaptan is what makes the gas smell stronger as the cylinder empties.
So, if you notice a stronger smell coming from your LPG cylinder, it's a sign that it's running low on gas and needs to be replaced soon. It's essential to keep an eye (or nose) on the smell to prevent any unexpected interruptions in your gas supply.
So, the smell from LPG cylinders when they're about to go empty is due to the increased concentration of the odorant added to the gas for safety purposes. It serves as a warning sign for you to refill or replace your cylinders before they run out completely, making sure of a continuous and safe supply of gas.