Potential risks of nitrogen as a reliable backup for instrument air

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Many factories now use nitrogen as a reliable backup for instrument air, and its safety risk management deserves attention. Here, relevant information on accidents and similar matters is provided for reference: 1. From Chemical Process Safety: Learning from Case History (pages 41–45). There was a leak in the instrument air pipeline in the control room, and at the same time work was being carried out on the instrument air system; as a result, large amounts of nitrogen entered the control room. Fortunately, safety technicians were there with portable oxygen meters, which prevented any occurrence of suffocation. When a worker entered the lounge, he found that his cigarette would not stay lit; this situation saved his life, as subsequent tests showed that the oxygen level had dropped below 16%. A few months earlier, operators had used instrument air in this small lounge as power for fan operation (or for direct ventilation). A company installed acoustic and optical alarm systems; when nitrogen began to replace the air used in the control instruments, it promptly evacuated unrelated personnel, inspected the relevant confined spaces, and locked them down. Additionally, the company installed oxygen monitoring devices on the exterior walls at the entrance points. 2. Employees at a polysilicon factory in China replaced the air inside a reduction furnace with instrument air before entering the furnace to carry out work. Due to the excessive use of instrument air, nitrogen was automatically supplied, resulting in the death of the workers from asphyxiation. Here, it is recommended that when constructing or conducting safety audits on existing installations, attention be paid to relevant risks, particularly by carrying out nitrogen asphyxiation risk assessments in confined spaces where instruments are installed. In addition, when performing restrictive control operations, be aware of the potential risk associated with using instrument air for replacement. Note: This is a post posted by the original poster a few months ago; it couldn’t be found for some reason, so it’s being reposted here.