Section 112(j) of the Clean Air Act as amended in 1990 requires owners or operators of major sources to apply for a Title V permit should the Environmental Protection Agency fail to promulgate emission standards for an applicable source category within 18 months after the date specified in the regulatory schedule established through Section 112(e) of the Act. The Title V permit that is issued must require the owner or operator to meet a maximum achievable control technology (MACT) emission limitation for all hazardous air pollutant (HAP) emissions within the source category. Regulations to implement Section 112(j) are codified in 40 CFR Part 63, Subpart B. This document provides guidance for complying with these regulations by identifying and evaluating control technology options to determine the MACT emission limitation. In this document, the term 'control technology' is defined broadly to be consistent with section 112(d)(2) of the Clean Air Act to include measures, processes, methods, systems or techniques which reduce the volume of, or eliminate emissions of, HAP through process changes, substitution of materials or other modifications; enclose systems or processes to eliminate emissions; collect, capture or treat HAP when released from a process, stack, storage or fugitive emissions point; are design, equipment, work practice, or operational standards; or a combination of the above.