Cultural relics carry the civilization and history of a nation, and the protection of cultural relics is very important for the inheritance of historical civilization. Cultural relics are irreplaceable and cannot be restored once they are damaged. The preservation of cultural relics has high requirements for its sealing, and it is necessary to maintain the independence of cultural relics. Usually, cultural relics museums use glass cabinets, warehouses, storage boxes, etc. to store cultural relics, but because air quality and environmental changes are usually uncontrollable, the economy is developing rapidly, the process of urbanization is accelerating, the construction of various factories and the increase in automobile exhaust emissions have aggravated the degree of air pollution, which has a great impact on the natural environment and human society. Among them, air pollution is closely related to the preservation of cultural relics.

Cultural relics are the carrier of history and culture. In order to ensure the inheritance of culture, it is necessary to set up a special custody organization to effectively keep it. In this process, the concentration of pollutants in the air will affect the preservation of cultural relics. Analyze the impact of air pollutants on cultural relics and the adverse consequences in the preservation of cultural relics. In order to strengthen the protection of cultural relics and better inherit the national culture, the relevant measures for the preservation of cultural relics are put forward. There are two main points in the protection of cultural relics: human factors and natural factors

1、human influencing factors

Cultural museums are inevitably affected by human factors in museums. For example, museum staff will inevitably have direct contact with cultural museums in handling, sorting, cleaning, and transportation, which will cause unconscious bumps and scratches on cultural relics. In addition, some of the visitors with low quality will "hands and feet" on cultural relics, even theft, violence, fire and other scenes, which have brought great threats and disasters to cultural relics. These intentional or unintentional human factors will be encountered in actual work, once it occurs, it will be irreparable, causing serious losses.

2, natural factors

Ambient temperature and humidity。Cultural relics need to be displayed on the showcase for tourists to watch. The temperature and humidity in the showcase where the cultural relics are located will have varying degrees of impact on the cultural relics. Excessive temperature will cause accelerated aging of the materials of the cultural relics, but too low temperature can not guarantee the comfort of tourists. The museum is an open place, and it is normal for people to come and go, so it is difficult to control the ambient temperature of the cultural museum. Humidity is a more critical factor. Excessive humidity will cause chemical reactions to some cultural relics, such as metal artifacts, wood products, bamboo products, calligraphy and painting works, etc., but too dry will make some materials brittle. Only by keeping a relative scientific humidity can the life of cultural relics be effectively improved.

Air Pollution and Microbiological Hazards。The museum receives a large number of visitors, which is difficult to control in the air. Many gases in the air will cause harm to the collection, such as carbon monoxide, carbon dioxide, ammonia, nitrogen oxide gas and other polluting gases. The gas intrudes into the cultural relics in the form of diffusion, so the gas is easy to enter the exhibition cabinet and erode the cultural relics. The long-term erosion of the gas with high acidity and alkalinity will cause serious damage to the cultural relics. Microbial hazards refer to some bacteria, molds, pests and other organisms. The cultural relics also need to be ventilated in the exhibition cabinets of the museum, so it brings opportunities to these tiny creatures.

Among them, carbon dioxide can be combined with water in the air to form carbonic acid, which causes corrosion to stone metal relics such as white marble and bronze. This damage phenomenon is clearly visible in the Forbidden City. Carbon dioxide in the urban atmosphere mainly comes from respiration. Due to the growth of population and the increase of fuel, the concentration of carbon dioxide in the atmosphere is increasing. The Forbidden City is an open unit with dense personnel and large flow of people, resulting in high carbon dioxide concentration. The instantaneous concentration reached 264 mg /m3 during the peak visit period. After testing, the concentration of carbon dioxide in the atmosphere of the Forbidden City is closely related to the flow of visitors. When the number of visitors is the largest, the instantaneous concentration of carbon dioxide reaches the maximum. In the static state, the instantaneous concentration of carbon dioxide decreased significantly. Because the cultural relics are in a high concentration of carbon dioxide environment for a long time, it will certainly have a destructive effect. Therefore, in addition to preventing the rapid and obvious destruction of cultural relics by strong acid gases such as sulfur dioxide and nitrogen dioxide, the destruction of cultural relics by carbonic acid formed by CO2 gas and water gas should not be underestimated.

Therefore, the purification and humidity control machine in the Wen Museum, in addition to the important parameter of temperature and humidity, will increase the carbon dioxide sensor to monitor the change of indoor carbon dioxide concentration in real time. Sensors provide accurate indoor air quality data by accurately measuring and monitoring CO2 levels, helping museum managers understand and control environmental conditions. At the same time, the sensor can detect the excessive carbon dioxide concentration in time, and automatically trigger the ventilation system to realize the circulation and freshness of indoor air. This helps to reduce the concentration of carbon dioxide, improve the indoor environment, and protect cultural relics and exhibits from potential damage.

Therefore, suitable temperature and humidity are necessary conditions for the protection of cultural relics. General temperature and humidity measurement will use the temperature and humidity sensor, the following recommend two temperature and humidity sensor HC2A-S and HTW-211. Among them, the HC2A-S measurement accuracy is high and the long-term stability is good. The measurement accuracy (@ 20+10 ℃):+0.8%RH,+0.1 ℃, which is suitable for places with high accuracy requirements. The HTW-211 is an accurate and reliable humidity measurement sensor based on HumiChipR. The humidity output of the sensor has been temperature compensated and is a linear voltage, which can be directly connected to a microcomputer with ADC input suitable for low-cost locations.

Acting British GSS brand low concentration infrared carbon dioxide sensor COZIR-LP3-5000, as well as South Korea SOHA SH-DS-005. It can achieve high-precision measurement in the range of 5000ppm, which COZIR-LP3-5000 ultra-low-power CO2 sensors with an average value of <3.3mw. It does not consume too much energy when running for a long time, which helps to improve the energy efficiency performance of the system. The advanced technology and quality control measures used in the sensor ensure its reliability and long-term stability under different environmental conditions.