A demister is a wire or fabric mesh (usually made of plastic or metal) through which gaseous media flow and on which droplets in the gas are separated due to their inertia (droplet separator).

In contrast to swirl droplet separators, demisters are relatively simple and inexpensive. They quickly reach their limits or require servicing or replacement if the gaseous medium contains not only droplets but also particles or components that tend to cake (grease, gels, etc.) in the gas flow.

To counteract poorer separation performance or more pressure loss, which can quickly cause a blockage, demisters cannot be rinsed or regenerated during the process.