5.1 The lower temperature limit of flammability is the minimum temperature at which a liquid (or solid) chemical will evolve sufficient vapors to form a flammable mixture with air under equilibrium conditions. Knowledge of this temperature is important in determining guidelines for the safe handling of chemicals, particularly in closed process and storage vessels.

Note 1: As a result of physical factors inherent in flash point apparatus and procedures, closed-cup flash point temperatures are not necessarily the minimum temperature at which a chemical will evolve flammable vapors (see Appendix X2 and Appendix X3, taken in part from Test Method E502). The temperature limit of flammability test is designed to supplement limitations inherent in flash point tests (Appendix X2). It yields a result closely approaching the minimum temperature of flammable vapor formation for equilibrium situations in the chemical processing industry such as in closed process and storage vessels.

Note 2: As a result of flame quenching effects existing when testing in standard closed-cup flash point apparatus, there are certain chemicals that exhibit no flash point but do evolve vapors that will propagate a flame in vessels of adequate size (X3.2). The temperature limit of flammability test chamber is sufficiently large to overcome flame quenching effects in most cases of practical importance, thus, usually indicating the presence of vapor-phase flammability if it does exist (6.2).

Note 3: The lower temperature limit of flammability (LTL) is only one of several characteristics that should be evaluated to determine the safety of a specific material for a specific application. For example, some materials are found to have an LTL by this test method when, in fact, other characteristics such as minimum ignition energy and heat of combustion should also be considered in an overall flammability evaluation.

5.2 The vapor concentration present at the lower temperature limit of flammability equals the lower flammable limit concentration as measured by Test Method E681 and extrapolated back to the same temperature. (This permits estimation of lower temperature limits of flammability if vapor pressure and concentration limit of flammability data are available (A2.3). A comparison of results of the tests, thus, affords a check on test reliability, the reliability of vapor pressure data, or both.)

1.1 This test method covers the determination of the minimum temperature at which vapors in equilibrium with a liquid (or solid) chemical will be sufficiently concentrated to form flammable mixtures in air at atmospheric pressure. This test method is written specifically for determination of the temperature limit of flammability of systems using air as the source of oxidant and diluent. It may also be used for other oxidant/diluent combinations, including air plus diluent mixtures; however, no oxidant/diluent combination stronger than air should be used. Also, no unstable chemical capable of explosive decomposition reactions should be tested (see 8.3).

1.2 This test method is designed and written to be run at local ambient pressure and is limited to a maximum initial pressure of 1 atm abs. It may also be used for reduced pressures with the practical lower pressure limit being approximately 13.3 kPa (100 mm Hg). The maximum practical operating temperature of this equipment is approximately 150°C (302°F) (Note A1.2).

1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.

1.4 This standard should be used to measure and describe the properties of materials, products, or assemblies in response to heat and flame under controlled laboratory conditions, and should not be used to describe or appraise the fire hazard or fire risk of materials, products, or assemblies under actual fire conditions. However, results of this test may be used as elements of a fire risk assessment which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific safety precautions are given in Section 8.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.