1.1 这些试验方法包括在规定的初始压力和初始温度下测定氧（氧化剂）和惰性气体与易燃气体和蒸汽的混合物的极限氧（氧化剂）浓度。 1.2 这些试验方法也可用于确定除氧气外的氧化剂的极限浓度。 1.3 不同燃烧状态（如热火焰、冷火焰和放热反应）之间的区别超出了这些试验方法的范围。 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 这些测试方法应用于测量和描述材料、产品或组件在受控实验室条件下对热和火焰的响应特性，而不应用于描述或评估材料、产品或组件在实际火灾条件下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。 1.6 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。 1.7 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 一些化学过程的安全操作需要了解极限氧（氧化剂）浓度。为了启动或操作反应堆，同时避免在其中产生易燃气体成分，或安全储存或运输材料，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。 5.2 LOC数据应用示例见参考文献 ( 3- 5. ) . 注2: 参考文献中报告的LOC值 ( 6- 8. ) ，并依赖于许多现代安全标准（如NFPA 69和NFPA 86）主要在直径为5厘米的易燃管中获得。该直径可能太小，无法减轻火焰熄灭的影响，从而妨碍准确测定大多数燃料的LOC。第节中规定的4升最小体积 7. 直径至少为20厘米。因此，使用这些试验方法确定的一些LOC值比之前在易燃管中测量的值大约低1.5 vol%，更适合用于火灾和爆炸危险评估研究。 5.3 以前的文献大多是LOC数据 ( 6- 8. ) 在可燃性管中测量。 5.4 Zlochower报告了在20-L和120-L试验箱中使用这些试验方法确定的五种参考气体的可接受LOC值（当氮气为惰性气体时） ( 9 ) ，总结如下: 氢 -120-L为4.6%，20-L为4.7% 一氧化碳 -120升时为5.1% 甲烷 -120-L为11.1%，20-L为10.7% 乙烯 -120-L为8.5%，20-L为8.6% 丙烷 -120升10.7%，20升10.5% 注3: 对于一氧化碳，结果对密封室内试验混合物的湿度敏感。 少量水蒸汽的存在通过为链支化反应提供氢（H）和羟基（OH）自由基，促进燃烧并促进火焰传播。对于保守结果，规定将试验空气加湿至接近饱和。 5.5 这些测试方法通常用于确定初始处于或接近大气压的气体和蒸汽的LFL（可燃下限）和UFL（可燃上限）。Zlochower报告了使用这些试验方法确定的五种参考气体的可接受LFL和UFL值 ( 9 ) . 5.6 这些试验方法还用于确定易燃气体的最大含量，当与规定的惰性气体混合时，该气体在空气中不易燃（ISO 10156，CGA P-23）。 5.7 对于用于测试设备调试（鉴定）和数据质量定期验证的标准参考气体，建议最低纯度为99%。

1.1 These test methods cover the determination of the limiting oxygen (oxidant) concentration of mixtures of oxygen (oxidant) and inert gases with flammable gases and vapors at a specified initial pressure and initial temperature. 1.2 These test methods may also be used to determine the limiting concentration of oxidizers other than oxygen. 1.3 Differentiation among the different combustion regimes (such as the hot flames, cool flames, and exothermic reactions) is beyond the scope of these test methods. 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 These test methods 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. 1.6 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. 1.7 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 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 or operate a reactor while avoiding the creation of flammable gas compositions therein, or to store or ship materials safely. NFPA 69 provides guidance for the practical use of LOC data, including the appropriate safety margin to use. 5.2 Examples of LOC data applications can be found in references ( 3- 5 ) . Note 2: The LOC values reported in references ( 6- 8 ) , and relied upon by a number of modern safety standards (such as NFPA 69 and NFPA 86) were obtained mostly in a 5-cm diameter flammability tube. This diameter may be too small to mitigate the flame quenching influence impeding accurate determination of the LOC of most fuels. The 4-L minimum volume specified in Section 7 would correspond to a diameter of at least 20 cm. As a result, some LOC values determined using these test methods are approximately 1.5 vol % lower than the previous values measured in the flammability tube, and are more appropriate for use in fire and explosion hazard assessment studies. 5.3 Much of the previous literature LOC data ( 6- 8 ) were measured in the flammability tube. 5.4 Accepted LOC values (when nitrogen is the inert gas) determined for the five reference gases using these test methods in 20-L and 120-L test enclosures have been reported in Zlochower ( 9 ) , and are summarized below: Hydrogen —4.6 % in 120-L, 4.7 % in 20-L Carbon Monoxide —5.1 % in 120-L Methane —11.1 % in 120-L, 10.7 % in 20-L Ethylene —8.5 % in 120-L, 8.6 % in 20-L Propane —10.7 % in 120-L, 10.5 % in 20-L Note 3: For carbon monoxide, results are sensitive to the humidity of the test mixture in the enclosure. Presence of a small concentration of water vapor facilitates combustion and promotes flame propagation by supplying the hydrogen (H) and hydroxyl (OH) free radicals for the chain branching reactions. For conservative results, provisions are made to humidify the test air to near saturation. 5.5 These test methods are often used to determine the LFL (lower flammability limit) and UFL (upper flammability limit) of gases and vapors initially at or near atmospheric pressure. Accepted LFL and UFL values determined for the five reference gases using these test methods have been reported in Zlochower ( 9 ) . 5.6 These test methods are also used to determine the maximum content of flammable gas which, when mixed with specified inert gas, is not flammable in air (ISO 10156, CGA P-23). 5.7 A minimum purity of 99 % is recommended for the standard reference gases used for the commissioning (qualification) of the test apparatus and for the periodic verification of data quality.