Each allowance permits one ton of SO 2 to be released into the air. For each ton of SO 2 discharged, one allowance is expended, and can not be used again. At the end of each year, polluting sources must hold enough allowances to cover their SO 2 emissions for that year. Any remaining allowances can be sold, traded, or banked for future use. If a source of air pollution does not have enough allowances to cover its SO 2 emissions, it can buy allowances on the open market.
Allowances are a valuable and tradable commodity.
Attainment of sulfur dioxide limits has also occurred more quickly than expected. Emission allowances have typically been given by regulators to large sources of pollution, and allow those sources to release a prescribed amount of a pollutant. Surplus allowances can be sold, traded, or banked for future use. Offsets Geographical regions that are not in compliance with an air quality standard are classified as non-attainment areas. Construction of new sources of air pollution or expansion of existing sources in these areas would be prohibited since it would exacerbate already high levels of pollution.