This part ANSI/ISA-12.13.01 (IEC 61779-1 through 5 Mod) specifies general requirements for construction and testing and describes the test methods that apply to portable, transportable and fixed apparatus for the detection and measurement of flammable gas or vapor concentrations with air. The apparatus, or parts thereof, are intended for use in potentially explosive atmospheres. This document is supplemented by the following parts, concerning the specific requirements for performance of the various types of apparatus:

Part 4: Performance requirements for group II (non-mining) apparatus indicating up to a volume fraction of 100% lower explosive limit

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