Pollution control, in environmental engineering, any of a variety of means employed to limit damage done to the environment by the discharge of harmful substances and energies. Specific means of pollution control might include refuse disposal systems such as sanitary landfills, emission control systems for automobiles, sedimentation tanks in sewerage systems, the electrostatic precipitation of impurities from industrial gas, or the practice of recycling. For full treatment of major areas of pollution control, see air pollution control, wastewater treatment, solid-waste management, and hazardous-waste management. There are many kinds of equipment which can be used to reduce particulate emissions. Physical separation of the particulates from the air using settling chambers, cyclone collectors, impingers, wet scrubbers , electrostatic precipitators, and filtration devices, are all processes that are typically employed. Another means of controlling both particulate and gaseous air pollutant emission can be accomplished by modifying the process which generates these pollutants. For example, modifications to process equipment or raw materials can provide effective source reduction. Also, employing fuel cleaning methods such as desulfurization and increasing fuel-burning efficiency can lessen air emissions.