- Downward displacement of air: This method can be used to collect gases that are heavier than air, like carbon dioxide or chlorine, at room temperature. The gas is generated in a flask or beaker and then allowed to flow into an inverted container placed over it. The heavy gas displaces the lighter air inside the container and gradually fills it up.

- Upward displacement of water: This method is suitable for collecting gases that are lighter than water, such as hydrogen or helium. A container filled with water is inverted and placed in a water-filled trough. The gas is generated in a separate flask or beaker and then carefully introduced into the upturned container through a delivery tube. The rising gas bubbles push the water down and occupy the upper space in the container.

Both methods rely on the principle of gas pressure and density differences. The heavier-than-air gas flows downward due to its higher density, while the lighter-than-air gas rises upward by displacing the water due to its lower density.