Difference between Fire Hazard Class A2 and Class A4
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In Table 3.1.3 of the Building Code (2018), which classifies the fire hazard of stored substances, item 2 refers to solid substances that can produce gases with an explosion limit of less than 10% when exposed to water or water vapor in the air. The listed substances are: calcium carbide, aluminum carbide. 4. Substances that, at room temperature and in contact with water or water vapor in the air, can produce flammable gases that lead to combustion or explosion. The listed substances include: potassium, sodium, lithium, calcium, strontium metals; lithium hydride, sodium hydride, **lithium aluminum hydride ； So what is the criterion for distinguishing between these two substances? Does Category 4A mean that it catches fire or explodes very quickly? Are sodium borohydride and potassium borohydride classified as Category M2 or Category M4? These two substances are not listed in the Construction Regulations and Petrochemical Regulations. Feel free to answer questions.
Is the standard being checked the release version? Was there a mistake?
Hello, thank you for your reply. The above refers to Table 3.1.3. May I ask, which category do you think it belongs to?
What was asked was the fire hazard classification of the stored substances; using the fire classification for production certainly won’t do. My understanding is that Category A4 should include the substances in Category A2, but Category A2 is listed separately as a special case, mainly referring to special substances such as calcium carbide and aluminum carbide. Sodium borohydride and potassium borohydride are solids; the flammable gas produced when these substances come into contact with water is hydrogen. The lower explosion limit of hydrogen is less than 10%, so the storage fire category can be classified as Class A2.
The gauge on the 2nd floor is very clear; Category A2 refers to gases and does not include solids. If the gauge on the 2nd floor is not applicable to the problem you described, it is necessary to consider whether 2 and 4 can be used together. Just like the 8 categories of hazardous chemicals, they are incompatible; only hazards from other categories are permitted, with classification being just one of them. It seems that compatibility is allowed here. Sodium borohydride is category 4 with no issues; as for whether it’s category 2, that’s hard to say
Can’t figure it out. The calcium carbide from the calcium carbide plant is stored openly under a shed
If it’s not poison gas, it’s safer to keep it open rather than closed
I believe that the classification for storage hazard levels essentially follows that of production hazard levels (with additional provisions made taking into account the differences between storage and production). Production Category A2 includes only gases, while Storage Category A2 mainly involves gases as well; several solids are specifically mentioned (probably due to the special characteristics of storage). Logically speaking, sodium borohydride and potassium borohydride (solid substances that are not mentioned) should belong to Category A4. This is just my personal opinion based on limited understanding! (Distinguish by comparing with the explanations of the provisions in the appendix of the Building Code)