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Compressed air is widely used in the pharmaceutical production process, such as in the large-scale fermentation of vaccines, in the preparation of vaccine semi-finished products, in the use of mixing and dilution tanks for bulk solutions and formulated solutions, in the transfer and purging of materials, in maintaining pressure after sterilization of process systems, and in the control of pneumatic components. Since the quality of compressed air that comes into direct contact with drug production directly affects the quality of the products, in order to ensure its quality, it is necessary not only to carry out strict purification processes on the compressed air but also to control its oil and water content. Composition of a clean compressed air system: The compressed air and purification system generally consists of equipment for generating, processing, and storing compressed air; such a system is known as the air supply system, or air compression system. Functionally, a compressed air system can be divided into the following parts: 1) The part that generates compressed air: such as air compressors and their control systems, cooling water systems, etc ； 2) Compressed air treatment section and post-treatment equipment: such as dryers, filters, separators, etc ； 3) Compressed air delivery section: such as air storage tanks, pipelines, valves, etc. Working principle of a clean compressed air system: Air comes into contact with machine components during compression and transportation processes, and as a result, the compressed air produced by air compressors may contain numerous harmful impurities, including water, water mist, water vapor, and condensed water ； Oils, including oil mist and oil vapor ； Various solid substances, such as rusty sludge, metal powder, rubber dust, tar particles, and fine particles of filter materials and sealing materials ； There are also various harmful chemical odors and substances. If not removed using appropriate methods, it will not only cause damage to the air supply system but also have the following adverse effects in practical use: 1) Microorganisms and particles in compressed air can contaminate sterile products ； 2) Oil vapor mixed in compressed air accumulates to a certain extent, forming an explosive and flammable hazard; moreover, when lubricating oil vaporizes, it produces an organic acid that can easily corrode the inner surfaces of compressed air pipelines as well as pneumatic components ； 3) Tiny particles mixed in (such as dust, rust, etc.) can easily damage pneumatic components and clog the throttle holes; worse still, they can cause serious contamination of the material ； 4) The moisture mixed in compressed air will reach saturation and form water droplets under certain temperature and pressure conditions; when compressed air comes into contact with the material, it can easily have a serious impact on the quality of that material ； 5) Excessively high compressed air temperature and the formation of water pose an absolute threat to the production of vaccines and bacterins. Therefore, compressed air used in the pharmaceutical industry must undergo purification processes such as cooling, oil removal, water removal, removal of solid dust particles, and sterilizing filtration before being delivered to the point of use, in order to meet the requirements of drug production. Firstly, using an oil-free air compressor can reduce the entry of oil contamination from the upstream stage. However, to ensure oil-free conditions, it is also necessary to take into account oil contamination in the surrounding environment; thus, even if an oil-free compressor is used at the upstream end, oil removal is still required at the downstream end. The compressed air passes through a moisture separator to separate the oil and water mixture, then goes through a refrigerated dryer for initial water removal. After that, another moisture separator is installed downstream of the refrigerated dryer for further separation. Following this, an oil-stabilizing filter is used, followed by four stages of filtration to remove dust and water. Finally, a sterilizing filter is employed to eliminate moisture, oil, suspended particles, and microorganisms from the compressed air, ensuring that the levels of these substances in the compressed air meet the standards required for clean compressed air. Quality standards for compressed air: To standardize these criteria, the Technical Committee on Air Compressors, Pneumatic Machinery and Tools (TC118) under the International Organization for Standardization (ISO) established international standards in 1986 regarding equipment for drying and purifying compressed air as well as the quality of compressed air itself. According to ISO 8573.1, which defines the quality grades of compressed air, contaminants in compressed air can be categorized into three types: solid impurities, water, and oil. In China, ISO 8573 has been adopted as the national standard GB/T 13277-91 titled “Quality grades of compressed air for general use”. In 2001, the ISO standards organization revised ISO8573.1, with the main changes relating to the requirements for solid particles. The new standards specify the quantity of solid particles; this change takes into account the actual performance of fiber filters, and it is relatively easy to detect, as shown in Table 1: https://pic.ouryao.com/data/attachment/forum/202110/09/124757bbr34lgyti4ita7b.png.thumb.jpg. Standards for the quality of clean compressed air used in pharmaceutical applications: The **Food and Drug Administration** set out the technical requirements for pharmaceutical-grade compressed air in the “Guidelines for Pharmaceutical Production Validation” (2003), as shown in Table 2. https://pic.ouryao.com/data/attachment/forum/202110/09/124807pynwpknzn3no2onn.png.thumb.jpg For compressed air that has undergone terminal sterilization filtration, the microbial count should be <1 cfu/m3. Quality standards for clean compressed air in enterprises: At present, there are no official international or ** quality standards for clean compressed air used in pharmaceutical production. By referring to the aforementioned quality grade standards as well as the GMP requirements regarding air purity, and by conducting a comprehensive assessment of these quality criteria along with the actual needs of the enterprise and the available testing methods, quality standards for clean compressed air within enterprises have been established. Drug safety remains an issue that cannot be ignored. Compressed air in the pharmaceutical industry plays an extremely important role in drug quality. The many problems that currently exist in design, construction, and operation management should attract serious attention from the relevant authorities, who should gradually regulate practices based on the actual conditions in each stage. Furthermore, as automation improves and unmanned operation becomes feasible, the biggest source of pollution from compressed air will surely be eliminated, thereby ensuring the sterility of clean rooms on a fundamental level. Furthermore, further optimizing the compressed air system in the drug production process by upgrading it to be more efficient and clean, thereby improving its operational efficiency, will be an important task that brings significant economic and social benefits.