Theory:

While your mom cooking some food in your home you can feel that delicious aroma coming to you even though you're in another room. Have you ever wondered how that smell came to you?
 
And we all like balloons right? but have you ever wondered how the balloon seller fillings a large number of balloons in a short span of time?
 
Then we all using LPG as our fuel to cook in our home and we use the oxygen cylinder in hospitals, have you ever wondered what is the science behind all of these?
 
The answer for all the above questions is gaseous particles.
Gas particles:
 
Gases are highly compressible as compared to solids and liquids. In gaseous state, the particles move about randomly at high speed.
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Because of the gases are highly compressible, we can use those gases in LPG in highly compressed condition. If we compress the gas particles, we can store the it in small container too.
 
We know that gas particles have more freely movable particles, so it can travel through the air easily. That's why the aroma of a food coming to you even though you're in another room.
 
Remember that the inter molecule force in the gaseous substance is the weakest force compare to the liquid and solid. This weakest inter molecule force makes the gaseous matter move freely to the air.