A wide variety of equipment can be used to clean dirty air. Air quality permits help minimize, reduce or prevent emissions as much as possible by placing requirements on how things are done.
Permits can specify the quantity, type, or quality of fuel or other substance used in a process.
For example, a permit might specify the maximum percent of sulfur that can exist in the coal to reduce sulfur dioxide emissions. A permit may specify the quantity of volatile chemicals in paint, solvent, adhesive or other product used in large quantity during manufacturing. Permits can also help reduce the impact of emitted pollutants on local air by specifying smokestack height and other factors. Engineers can also set combustion specifications to minimize emissions. For example, to help reduce nitrogen oxide formation, the combustion conditions in the furnace can be altered.