EMx is principally known as a catalytic technology for controlling combustion-generated NOx emissions. However, at its heart there is a potent oxidation catalyst and other basic surface chemistry components capable of 99% reduction of CO, organic compounds, SOx and high performance removal of particulate matter. In its basic configuration EMx consists of two active components. The first is a regenerable SOx guard bed. The second is the lean NOx trap. As exhaust gases pass through the system SO₂ is oxidized to sulfate and trapped on the guard bed. NOx is then oxidized to NO₂ and trapped on the surface of the NOx trap. Both of these units are periodically regenerated with a stream of dilute hydrogen, releasing the NOx as molecular nitrogen and the sulfur as SO₂ (which can be collected and removed from the gas stream).  However, while NOx and SOx are being adsorbed other processes are also taking place. CO and hydrocarbons are readily oxidized, often leading to non-detectable levels at the system exhaust. Also, significant reductions in particulate matter – particularly the condensable inorganic fraction – have been measured, suggesting a mechanism for soot oxidization. This points the way for further developments in the technology with positive implications for airshed regions such as California's South Coast Basin and San Joaquin Valley, and Texas' greater Houston area.