Determination of CO medium toxicity in the pressure pipeline characteristics table
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The “Announcement by the State Administration for Market Regulation on Matters Related to Administrative Licenses for Special Equipment” (No. 3, 2019) classifies industrial pipelines as follows: GC1 grade: 1. Process pipelines that transport media with an acute toxicity level of Category 1 as specified in the “Catalogue of Hazardous Chemicals”, gas media with acute toxicity of Category 2, and liquid media with acute toxicity of Category 2 whose operating temperature is higher than their standard boiling point； Toxicity is determined by referring to the \"Catalogue of Hazardous Chemicals (2015 edition)\") and its accompanying \"Classification Information Table for Hazardous Chemicals\" in order to assess the toxicity of a substance. However, the data descriptions for some substances are somewhat vague; for example, the categories marked with a \"*\" in note field (3) of the Classification Information Table indicate that, where there is sufficient evidence, those chemicals can be classified under stricter categories. For example, entry 498 \"1,3-dichloro-2-propanol\" is classified as \"Acute toxicity – oral, Category 3*\"; if there is sufficient evidence, it can be classified as the stricter category of \"Acute toxicity – oral, Category 2\". The same issue applies to carbon monoxide as a medium; its toxicity classification is “Acute Toxicity – Inhalation, Category 3*”. Due to the asterisk, if it were strictly classified as Category 2, it would be GC1, while if it is classified as Category 3, it would be GC2. This results in significant differences in the costs associated with pipeline inspection. I would like to ask everyone: in work involving CO media, how is toxicity defined in the pressure pipeline characteristic tables?
The * indicates that, when there is sufficient evidence, a higher level can be assigned; so what is this sufficient evidence? Tracing back to its origins, where does the definition of this acute toxicity – inhalation, Category 3, come from? As can be seen, this is the terminology used in the \"Hazardous Chemicals Classification Information Table.\" The basis for classifying each substance in this table is actually the \"Specifications for the Classification and Labelling of Chemicals\" (GB 30000-2013). Differences in classification arise due to varying perspectives; therefore, the former Work Safety Supervision Bureau organized experts to carry out standardized classification for most substances. The determination of acute toxicity is covered in Part 18 of the \"Specifications for the Classification and Labelling of Chemicals,\" with the main criterion being the acute toxicity estimate (ATE). This ATE value is ultimately derived from LC50/LD50 values as well as physiological tests. Therefore, the adequate basis are LC50/LD50 and physiological test data! You can take a look at the decision logic:
CO has always been highly toxic, and its toxicity cannot be determined using a scale of 1, 2, 3 as you mentioned
. HG/T20660 specifies clear toxicity; caution is required regarding CO
Acute toxicity of CO – inhalation poses a moderate hazard; the method described on floor 2 is approved. The list of highly toxic substances used on the 3rd floor refers to the catalog of highly toxic items; high toxicity and the hazards associated with high toxicity are two different concepts. Furthermore, the overall high hazard level is different from the high hazard level associated with acute toxicity alone. The overall CO rating is highly hazardous (for details, refer to HG 20660-2017 as described on page 4), but the acute toxicity – inhalation score is only 2 (rat inhalation LC50: 2070 mg/m3 over 4 hours), indicating a toxic hazard. In accordance with the classification requirements for industrial pressure pipelines outlined in the new Document No. 3, acute toxicity is the main factor considered; therefore, if no LC50 value lower than 500 can be found, the pipeline can be classified as Category 3. If such a value can be found, then classification will be determined based on that corresponding category.