1 Scope

1.1 This Standard provides a method, based on the results of specified flammability tests, for the classification of fluids or liquids as nonflammable, or as flammable with the degree of fire hazard rated both in general terms and on a numerical scale, in comparison with well-known products whose hazards have been established by field experience.

1.2 The classifications derived by this method are evaluations of the inherent flammability of liquids and their vapors. Increases in fire hazard due to partial evaporation of components of certain liquid mixtures during handling and use are taken into account in assigning the fire hazard classification. The assigned classifications do not apply when the liquid is dispersed in the atmosphere in the form of finely divided spray, mist, or fog.

1.3 The liquids may be pure chemical compounds, homogeneous mixtures or solutions, emulsions, or multilayer combinations of immiscible liquids. The liquid products may contain undissolved solid materials, either in suspension or as a separate layer.

1.4 This method of classification with respect to fire hazard is applicable to liquids which are essentially stable materials. Liquids susceptible to dangerous decomposition reactions during phase change or when exposed to heat or mechanical shock, and liquids subject to hazardous exothermic polymerization, are considered unstable materials within the intent of this Standard. It should be ascertained that the product is stable with respect to these features before applying the tests specified in this Standard. Evaluation of the more severe hazards presented by such unstable materials requires considerations which are beyond the scope of this Standard.

1.5 The classifications derived by this method are with respect to fire hazard only. The assigned ratings do not cover other potential hazards, including the physiological effects of the products, in any form, nor do they indicate the efficiency or effectiveness of the products in their intended uses.

Summary of Topics

This new edition of UL 340 was issued to incorporate the following changes in rerquirements:

Addition of Requirements for Transformer Mineral Oil, Vegetable Oil, and Natural Ester Oil to Tables 3.1 and 13.1