1.1 本试验方法旨在确定在20升或更大体积的近球形密闭容器中，分散在空气与惰性/不可燃气体混合物中的可燃粉尘的极限氧浓度。 1.2 从该方法获得的数据提供了尘云爆燃特性的相对测量值。 1.3 本试验方法应用于测量和描述受控实验室条件下材料对热和火焰的响应特性，不应用于描述或评估实际火灾条件下材料、产品或组件的火灾危险或火灾风险。然而，该测试结果可作为火灾风险评估的要素，该评估考虑了与特定最终用途火灾危险评估相关的所有因素。 1.4 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.5 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 第节给出了具体的预防说明 8. . 1.6 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 本试验方法提供了进行实验室试验以评估粉尘相对爆燃参数的程序。 5.2 一些化学过程的安全操作需要了解极限氧（氧化剂）浓度。为了启动、关闭或操作过程，同时避免在其中产生易燃粉尘气体环境，或安全气动运输材料，可能需要这些信息。NFPA 69为LOC数据的实际使用提供了指导，包括使用的适当安全裕度。 5.3 由于通过该方法测量的LOC可能随点火器能量和传播标准而变化，因此应将LOC视为相对测量而非绝对测量。 5.4 如果使用的点火源太弱，测得的LOC将高于“真实”值，并且不够保守。 这是一个可燃极限，而不是易燃极限，测试可以描述为“未充分驱动”理想情况下，增加点火能量，直到测得的LOC独立于点火能量（即“真实”值）。然而，在某些情况下，点火能量可能变得太强，不适合测试室的大小，系统变得“过度驱动”当点火器火焰相对于燃烧室体积变得过大时，测试可能会导致爆炸，而实际上只是点火器火焰中的灰尘燃烧，没有真正传播到点火器之外 ( 1- 3. ) . 5. 该LOC值过于保守。 5.5 测量20-L室中粉尘LOC的推荐点火源是2500-J烟火点火器。 6. 该点火器含有0.6 g 40%的粉末混合物 % 锆、30%硝酸钡和30%过氧化钡。 在几个点火能量下测量LOC将提供有关系统可能过驱动的信息，以评估20升燃烧室中可能过驱动的影响，也可以在较大的燃烧室（如1米燃烧室）中进行比较测试 3. 室 ( 1- 3. ) . 5.6 通过该测试技术获得的值特定于所测试的样品（尤其是粒度分布）和使用的方法，不被视为固有材料常数。 注1: 之前发布的大部分LOC数据 ( 4. ) . 在1.2升哈特曼室中使用火花点火源获得，可能不够保守。欧洲LOC测定方法EN 14034–4在20-L燃烧室中使用两个1000-J烟火点火器。

1.1 This test method is designed to determine the limiting oxygen concentration of a combustible dust dispersed in a mixture of air with an inert/nonflammable gas in a near-spherical closed vessel of 20 L or greater volume. 1.2 Data obtained from this method provide a relative measure of the deflagration characteristics of dust clouds. 1.3 This test method should be used to measure and describe the properties of materials 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 that takes into account all of the factors that are pertinent to an assessment of the fire hazard of a particular end use. 1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 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 precautionary statements 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. ====== Significance And Use ====== 5.1 This test method provides a procedure for performing laboratory tests to evaluate relative deflagration parameters of dusts. 5.2 Knowledge of the limiting oxygen (oxidant) concentration is needed for safe operation of some chemical processes. This information may be needed in order to start up, shut down or operate a process while avoiding the creation of flammable dust-gas atmospheres therein, or to pneumatically transport materials safely. NFPA 69 provides guidance for the practical use of LOC data, including the appropriate safety margin to use. 5.3 Since the LOC as measured by this method may vary with the energy of the ignitor and the propagation criteria, the LOC should be considered a relative rather than absolute measurement. 5.4 If too weak an ignition source is used, the measured LOC would be higher than the “true” value and would not be sufficiently conservative. This is an ignitability limit rather than a flammability limit, and the test could be described as “underdriven.” Ideally, the ignition energy is increased until the measured LOC is independent of ignition energy (that is, the “true” value). However, at some point the ignition energy may become too strong for the size of the test chamber, and the system becomes “overdriven.” When the ignitor flame becomes too large relative to the chamber volume, a test could appear to result in an explosion, while it is actually just dust burning in the ignitor flame with no real propagation beyond the ignitor ( 1- 3 ) . 5 This LOC value would be overly conservative. 5.5 The recommended ignition source for measuring the LOC of dusts in 20-L chambers is a 2500-J pyrotechnic ignitor. 6 This ignitor contains 0.6 g of a powder mixture of 40 % zirconium, 30 % barium nitrate, and 30 % barium peroxide. Measuring the LOC at several ignition energies will provide information on the possible overdriving of the system to evaluate the effect of possible overdriving in a 20-L chamber, comparison tests may also be made in a larger chamber such as a 1-m 3 chamber ( 1- 3 ) . 5.6 The values obtained by this testing technique are specific to the sample tested (particularly the particle size distribution) and the method used and are not to be considered intrinsic material constants. Note 1: Much of the previously published LOC data ( 4 ) . were obtained using a spark ignition source in a 1.2-L Hartmann chamber and may not be sufficiently conservative. The European method of LOC determination EN 14034–4 uses two 1000-J pyrotechnic igniters in the 20-L chamber.