Deterioration factor means the relationship between the highest emissions during the useful life and emissions at the low-hour test point, expressed in one of the following ways:
(1) For multiplicative deterioration factors, the ratio of the highest emissions to emissions at the low-hour test point.
(2) For additive deterioration factors, the difference between the highest emissions and emissions at the low-hour test point.
40 CFR § 1037.801
The following definitions apply to this part. The definitions apply to all subparts unless we note otherwise. All undefined terms have the meaning the Act gives to them. The definitions follow: