EPCRA Section 312 includes a two tier approach. Tier I requires information (such as maximum amount of hazardous chemicals at the facility during the preceding year, an estimate of the average daily amount of hazardous chemicals at the facility, and the general location) be aggregated and reported by hazard categories. Tier II not only requires the information mentioned above, but also requests information on specific location and storage.
Tier I is required by Federal law; however, Tier II is required only upon request by the local emergency planning committee or the State emergency response commission. However, a covered facility may submit Tier II forms instead of Tier I forms. Because most States require submittal of Tier II forms, in practice a typical facility in the US will submit a Tier II form only, which satisfies both Federal and State reporting requirements.