Three-phase and single-phase ac synchronous and induction electric machines in ratings 0.18 kW (1/4 hp) and larger are covered in this guide. Primary emphasis is on the use of open or nonexplosionproof or nonflameproof enclosed machines in Zone 2 and Class I, Division 2 locations as covered in National Electrical Code(R) (NEC(R)) (NFPA 70-2020) and Canadian Electrical Code(R) (CE code(R)) (CSA C22.1-2021 Safety Standard for Electrical Installations) as applicable. Surface temperature test methods and sine wave and non-sine wave applications are covered. Precautions against excessive surface temperatures and sparking are included. To help mitigate hot surface temperatures and sparking, this document provides guidance for selecting, operating, and maintaining machines in Zone 2 and Class I, Division 2 locations. This guide does not cover ac wound rotor machines and dc electric machines. Machines installed in locations other than Zone 2 and Class I, Division 2 as covered in NFPA 70-2020 or CSA C22.1 - 2021 are not covered in this guide. This document is not a specification and is not intended to be used as a specification for purchasing electric machines. The voltage breaks in this document are 1000 V and less, and over 1000 V.