![Ad Blue 300x175](https://img.forconstructionpros.com/files/base/acbm/fcp/image/2021/04/AdBlue_300x175.606b6e6732392.png?auto=format%2Ccompress&q=70&rect=0%2C3%2C300%2C169&w=250)
In 2004 the Environmental Protection Agency (EPA) signed the final rule introducing Tier 4 emission standards. The goals of the regulation are designed to preserve and improve health, but the rules also impact businesses making, selling, servicing, and purchasing portable air compressors and a wide range of other equipment with affected diesel engines.