What are the differences between Tier I and Tier II forms?

The reporting under Section 312 is in two tiers, Tier I and Tier II.  What are the general differences between the two forms?

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.

Finally, Tier I is required by federal law; 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.  Some states already require facilities to submit Tier II forms or forms created by the states under their legislation.