Defines the type of customer. The common classes of service applied to ultimate consumers, and considerably more completely described in the A.G.A. publication "Definitions of a Gas Customer and Classes of Service for Industry Reporting Purposes", are: 1.Residential Service: Covers service to customers for domestic purposes (single, multifamily, or mobile homes, etc.). In residential service, the number of housing units within a structure determines the customer classification. 2.Commercial Service: Covers service to customers engaged in wholesale or retail trade, agriculture, communications, finance, fisheries, forestry, government, insurance, real estate, transportation, etc., and to customers not directly involved in other classes of service. 3.Industrial Service: Covers service to customers engaged primarily in a process which either involves the extraction of raw materials from the earth or a change of raw unfinished materials into another form or product.