Is ammonia considered a highly hazardous substance?
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According to the standards HG/T20660-2017 and GB50517, ammonia is either of moderate hazard or low toxicity； However, GB50160 states as follows: 5.5.15 Liquids, flammable gases with low calorific value, flammable gases containing oxygen or halogen elements and their compounds, flammable gases with extremely high or high toxicity, inert gases, acidic gases, and other corrosive gases shall not be discharged into the plant-wide flare system; instead, separate emission systems or treatment systems must be installed. 5.5.15 Introducing combustible gases with a low calorific value into the flare system can disrupt the stable combustion of the flare or cause it to go out ； The release of oxygen-containing flammable gases into the flare system can result in the formation of explosive gases within that system and its facilities, which may lead to backfire and explosions, as well as damage to pipes or equipment ； Acidic gases and other corrosive gases can cause air pollution as well as corrosion of pipelines and equipment; therefore, a separate acidic gas flare should be installed. For gases with extreme or high toxicity or those containing corrosive substances, having separate treatment and emission systems in place helps ensure safe production. The toxicity classification should be determined in accordance with the \"Classification of Hazards from Occupational Exposure to Toxic Substances\" (GB5044) and the \"List of Highly Toxic Substances\" (Document No. 142 issued by the Health and Law Supervision Department). However, benzene and carbon monoxide emitted by petrochemical enterprises lose their toxicity after being fully burned in a flare system; therefore, such substances or combustible gases containing them can still be discharged into a public flare system. The presence of ammonia in the List of Highly Toxic Substances does it sufficiently indicate that ammonia is highly hazardous? ? ? So, is ammonia highly hazardous?
It is classified as moderately hazardous; the main issue is that the odor released is too strong, so stricter requirements are set
Isn’t the Toxicity Hazard Index (THI) for ammonia 51? Can’t it be highly toxic?
The underlying reason for this issue is not whether it is classified as one category or another, but rather what standards are followed in design and production. In practice, the formulation of petrochemical standards and chemical industry standards is not handled by a single authority; as a result, their standard systems differ, which leads to many inconsistencies. A reasonable solution: The project should follow the standards of the system used for its acceptance.
Liquid ammonia has strong permeability and can cause stress corrosion in carbon steel; the hazard is generally moderate. In particular, when designing flanges, studs, and gaskets, it is necessary to follow relevant standards for solid materials. It seems that for ordinary ammonia solutions at normal pressure, the requirements are not very strict; please refer to relevant guidelines
The standard GB50493-2009 classifies ammonia as a toxic gas.
It is generally considered to be of moderate severity
According to the GBZ standards, ammonia is indeed highly toxic