effusion
Another related process is effusion. Effusion is the process of a confined gas escaping through a tiny hole in its container. Effusion can be observed by the fact that a helium-filled balloon will stop floating and sink to the floor after a day or so. This is because the helium gas effuses through tiny pores in the balloon. Both diffusion and effusion are related to the speed at which various gas molecules move. Gases that have a lower molar mass effuse and diffuse at a faster rate than gases that have a higher molar mass. While they are similar processes, there is a key difference between diffusion and effusion. Diffusion describes the process of a gas spreading out at a constant pressure, such as throughout a room. Effusion, on the other hand, describes the process of a gas spreading out from a high pressure surroundings to lower pressure surroundings.