Under the Protocol, only the Annex I Parties have committed themselves to national or joint reduction targets (formally called "quantified emission limitation and reduction objectives" (QELRO) - Article 4.1).

Of the 261 units at 110 plant locations affected by Phase I emission limitations, five were oil-fired, five coal-fired units were retired, and one coal-fired unit was placed on cold standby status prior to passage of the legislation in 1990.

Nothing in this section shall preclude an owner or operator from installing and operating an alternative NOx control technology capable of achieving the applicable emission limitation.

If the permitting authority determines, in accordance with regulations issued by the Administrator that the conditions in the paragraph above can be met, the permitting authority shall issue operating permits for such units, in accordance with section 404 and title V, that allow alternative contemporaneous annual emission limitations.

Such emission limitations shall only remain in effect while both units continue operation under the conditions specified in their respective operating permits.

The Administrator is required, at least every eight years, to review and, if appropriate revise, these performance standards to reflect the degree of emission limitation achievable through application of the best system of emission reduction which the Administrator determines has been adequately demonstrated.

It allows for firms to place an imaginary bubble over the multiple point sources of its plant and to be given an overall maximum emission limitation for the bubble (figure 7.3).

Any such trading shall be supplemental to domestic actions for the purpose of meeting quantified emission limitation and reduction commitments under that article".

The "assigned amounts" are the Kyoto Protocol Annex B emission targets (or "quantified emission limitation and reduction objectives") expressed as levels of allowed emissions over the 2008-2012 commitment period.

Units subject to subsection (b)(1) for which an alternative emission limitation is established shall not be required to install any additional control technology beyond low NOx burners.