smell of cooked food spread fast bc when something is heated up, the kinetic energy of the molecules/particles increases and some of them even mix with the air and moves around. the first answer is also correct (i just explained it more detaily)
When we cook food in the kitchen, that's the region of higher concentration of the smell. By diffusion, the smell spreads to the whole room and thereby whole house, so anyone standing at a distance, can smell it.
