I. Types of laboratory gases       Common gases in laboratories include high purity gas used in precision instruments, experimental gas (chlorine gas) used in chemical reaction experiments, gas and compressed air used in auxiliary experiments, etc. High purity gases used in precision instruments such as gas chromatography, gas chromatography-mass spectrometry, atomic absorption spectrometry and ICP mainly include non-gas (nitrogen, carbon dioxide), inert gas (helium, argon), flammable gas (hydrogen, acetylene), combustion-supporting gas (oxygen) and so on.       Laboratory gas is mainly provided by gas cylinders, and individual gases can be provided by gas generators. Common external color distinctions and marks of steel cylinders: oxygen cylinders (sky blue and black characters), hydrogen cylinders (dark green and red characters), nitrogen cylinders (black and yellow characters), compressed air cylinders (black and white characters), acetylene cylinders (white and red characters), carbon dioxide cylinders (green and white and black characters), argon cylinders (gray and green characters) and helium cylinders (brown).           Second, the laboratory gas supply method       Laboratory gas supply system can be divided into decentralized gas supply and centralized gas supply according to its supply mode.       (1) Dispersed gas supply is to place gas cylinders or gas generators in each instrument analysis room, close to the gas point of the instrument, which is convenient to use, saves gas and has less investment; However, because the gas cylinder is close to the experimenter and its safety is not good, it is generally required to use explosion-proof gas cylinder cabinet, and wait for alarm function and exhaust function. Alarms are divided into combustible gas alarms and non-combustible gas alarms. The gas cylinder cabinet shall be equipped with gas cylinder safety warning signs and gas cylinder safety fixing devices.       (2) Centralized gas supply means that all kinds of gas cylinders needed by various experimental and analytical instruments are placed in independent gas cylinder rooms outside the laboratory for centralized management. All kinds of gases are transported from the gas cylinders to different experimental instruments in each laboratory in the form of pipelines according to the gas requirements of different experimental instruments. The whole system includes air source pressure control part (bus bar), gas transmission pipeline part (EP stainless steel pipe), secondary pressure regulating and distributing part (function column) and terminal part (joint and globe valve) connected with the instrument. The whole system is required to have good air tightness, high cleanliness, durability, safety and reliability, which can meet the requirements of uninterrupted and continuous use of various gases by experimental instruments. In the process of use, the whole or local gas pressure and flow are adjusted in full range according to the working conditions of experimental instruments to meet the requirements of different experimental conditions.       Centralized gas supply can realize centralized management of gas sources, stay away from laboratories and ensure the safety of laboratory personnel; However, the long gas supply pipeline leads to waste of gas, and it is inconvenient to open or close the gas source between gas cylinders.           III. Safety Code for Gas Cylinder Room and Gas Cylinder       (1) Gas cylinders should be used exclusively, and other kinds of gases cannot be modified at will.   (2) The cylinder chamber is strictly prohibited from being close to fire source, heat source and corrosive environment.   (3) Explosion-proof switches and lamps are not allowed in the gas cylinder room, and open flames are prohibited around.   (4) The cylinder chamber should be ventilated and kept cool, and the top of the cylinder chamber should be left with a drain hole to prevent hydrogen accumulation.   (5) Empty bottles and real bottles are placed in different areas. Gas cylinder compartment flammable and explosive gas cylinders should be isolated from auxiliary gas cylinders.   (6) Accessories such as bottle valve, nozzle screw and pressure reducing valve are in good condition, and there are no dangerous situations such as air leakage, slippery wire and loose gauge needle. All kinds of barometers are generally not allowed to be mixed.   (7) Gas cylinders must be placed upright during storage and use. When the working place is not fixed and moves frequently, they should be fixed on a special trolley to prevent dumping. It is strictly forbidden to use them horizontally.   (8) Gas cylinders are strictly prohibited from being close to fire sources, heat sources and electrical equipment, and the distance from open flames is not less than 10m. When oxygen cylinders and acetylene cylinders are used at the same time, they cannot be put together.   (9) After use, empty bottles should be moved to the empty bottle storage area, and marked with empty bottles. It is strictly forbidden to mix empty bottles with real bottles.   (10) The gas in the gas cylinder cannot be exhausted, and a certain residual pressure must be maintained.   (11) Gas cylinders shall be inspected regularly, and shall not exceed the inspection period of oxygen cylinders, acetylene cylinders and liquefied petroleum gas cylinders for 3 years, and the inspection period of argon cylinders and nitrogen cylinders for 5 years.   (12) Gas cylinders should be placed in the gas cylinder storage room outside the theme building. For the gas with daily gas consumption not exceeding one bottle, one cylinder of this kind of gas can be prevented in the laboratory, but the cylinder should have safety protection facilities.   (13) The storage room of hydrogen and nitrogen cylinders shall have ventilation measures of not less than three times per hour.       IV. Code for Design of Gas Pipelines       (1) Hydrogen, oxygen and gas pipelines and various gas pipeline branches introduced into the laboratory should be exposed. When hydrogen, oxygen and gas pipelines are laid in pipeline wells and pipeline technical layers, ventilation measures should be taken for 1 ~ 3 times/h.   (2) For general laboratories designed according to standard unit combination, all kinds of gas pipelines should also be designed according to standard unit combination.   (3) The gas pipeline passing through the wall or floor of the laboratory shall be laid in the embedded casing, and the pipe section in the casing shall not have welds. The pipe and casing are tightly sealed with non-combustible materials.   (4) Vent pipes should be set at the end and highest point of hydrogen and oxygen pipelines. The vent pipe should be more than 2m above the top of the layer and should be located in the lightning protection zone. Sampling points and purging ports should also be set on the hydrogen pipeline. The position of vent pipe, sampling port and purging port should meet the requirements of gas purging replacement in pipeline.   (5) Hydrogen and oxygen pipelines shall have grounding devices for conducting static electricity. The grounding and jumping measures of gas pipelines with grounding requirements shall be implemented according to the current relevant national regulations.   (6) Pipeline laying requirements   1) The pipeline for conveying dry gas should be installed horizontally, and the pipeline for conveying wet gas should have a slope of not less than 0.3%, with the slope facing the condensed liquid collector.   2) The oxygen pipeline and other gas pipelines can be laid on the same frame, and the distance between them shall not be less than 0.25 m. The oxygen pipeline shall be above other gas pipelines except oxygen pipeline.   3) When the hydrogen pipeline and its combustible gas pipeline are laid in parallel, the distance between them should not be less than 0.50 m; When cross laying, the spacing should not be less than 0.25 m. When laying in layers, the hydrogen pipeline should be located above. Indoor hydrogen pipelines should not be laid in trenches or directly buried. Do not pass through rooms where hydrogen is not suitable.   4) Gas pipelines shall not be laid on the same frame as cables and lines to stores.   (7) Seamless steel pipe should be used for gas pipeline. Stainless steel pipe, copper pipe or seamless steel pipe should be used for gas pipeline with gas purity greater than or equal to 99.99%.   (8) The connection section between pipeline and equipment should adopt metal pipeline. If it is a non-metal hose, PTFE pipe and PVC pipe should be adopted, and latex pipe should not be adopted.   (9) Material of valves and accessories: Copper materials shall not be used for hydrogen and gas pipelines, and copper, carbon steel and malleable cast iron may be used for other gas pipelines. Accessories and instruments used in hydrogen and oxygen pipelines must