1 Scope
This part of IEC 60079 provides guidance on classification of gases and vapours. It describes a test method
intended for the measurement of the maximum experimental safe gaps (MESG) for gas- or vapour-air mixtures under normal conditions of temperature1 and pressure so as to permit the selection of an appropriate group of equipment.
The method does not take into account the possible effects of obstacles on the safe
gaps 2. This standard describes also a test method intended for use in the determination
of the auto-ignition temperature of a chemically pure vapour or gas in air at atmospheric
pressure.
The tabulated values of chemical and engineering properties of substances are provided
to assist engineers in their selection of equipment to be used in hazardous areas.
It is hoped to publish further data from time to time, as the results of tests made
in several countries become available.
The scope of these data has been selected with particular reference to the use of
equipment in hazardous areas, and notice has been taken of standard measurement methods.
NOTE 1 The data in this standard have been taken from a number of references which are given
in the bibliography.
NOTE 2 Some variations in the data may appear when references are compared, but usually the
discrepancy is sufficiently small to be of no importance in the selection of equipment.