A gas scrubber is a piece of equipment designed to purify a plume of gases before it is released into the environment. Pollutants are removed from the plume, allowing for the venting of harmless compounds while the dangerous ones are trapped for sequestration and disposal. Scrubbers are required by law in settings where people work with potentially polluting gases, and there are several designs available for various applications.

One type of gas scrubber is a wet scrubber, where a liquid, often water, is introduced into the ventilation stack. The liquid is commonly sprayed, or aerosolized. It traps particulates in the gas and reacts with compounds in the gas, carrying them down to the bottom of the stack. The liquid pools for storage, at which point it can be run through a wastewater treatment plant and reused or otherwise processed to control the pollutants. It is common to see a visible plume when a wet scrubber is used, as some humidity is created.

In a dry gas scrubber, a compound is introduced in the form of a gas or powder. The compound clings to certain molecules in the escaping gases, trapping them so they cannot be released into the air. It is designed to sink or be transported through controlled vents, purifying the gases as they rise through the stack. The plume in this case may not be visible when it emerges from the stack, as particulates should be removed and humidity levels stay stable.

Scrubber systems usually need to be designed for specific applications, keeping in mind the type of pollutants involved and the volume of production. The scrubber must be designed to cope with peak loads without failing, as a shutdown of the stack could be extremely costly and, in some cases, dangerous. Scrubbers may also be fitted with filters and other devices, along with air quality monitoring systems for the purpose of confirming that they are functioning properly by removing hazards from the air and releasing only clean air into the environment.

Increasing clampdowns on permissible pollution in many regions of the world have forced companies to be innovative about pollution control. Gas scrubber design is constantly under improvement as people work on new systems for pulling out impurities in the air. Regulations are often designed to promote improvement through incentives or the establishment of deadlines for companies to meet new air quality standards with gas scrubber equipment and other anti-pollution measures.