Temperature, relative humidity, minimum static pressure difference, ventilation times, self-purification time, minimum fresh air volume, noise and minimum illumination are important technical indicators of the purification project of the operating department. These technical indicators determine whether the purification project is tested by comprehensive performance evaluation. Among them, self-cleaning time is the time required to reduce the dust concentration of the air after the removal of the waste in the operating room by about 90% or to the upper limit of the designed cleanliness level under the condition of normal ventilation times. The cleanliness of the clean room is classified according to the dust concentration in the air. It can be seen that there is dust in the air. Concentration is very important in purification engineering. The most effective way to reduce the dust concentration in air is to install filters in the air conditioning system.
In the purifying air conditioning system of the operating department, three-stage filters, i.e. primary filter, intermediate filter and sub-high-efficiency filter, are generally installed in the fresh air air air conditioning unit. Secondary filters are usually installed in circulating air conditioning units. A high efficiency filter is set at the end air supply port, and a medium and high efficiency filter is set at the return air outlet according to the positive and negative pressure. When the particulates of bacteria and viruses in the air are larger, the barrier air filter has higher filtration efficiency. At the beginning of the implementation of the purification project, the removal efficiency of bacteria by filters is incomparable with other disinfection methods, but it also has its drawbacks:
(1) The initial/final resistance of filters, especially high-efficiency filters, is generally about 250 kPa/500 kPa. If the resistance of filters is large, the extra pressure of the motor will increase, and the configuration of the air-conditioning system will be improved.
(2) The efficiency of high efficiency filter is very low for particles less than 0.5 um.
(3) High efficiency filters are usually replaced once every three to four years, which increases the cost of use. In view of the drawbacks of filters, with the continuous development of science and technology, new technologies have been applied to the medical purification industry. There are mainly electrostatic adsorption air purification and disinfection technology, ionomer air purification and disinfection technology and photocatalyst.
1 Electrostatic Adsorption Air Purification and Disinfection Technology
1.1 The working principle of electrostatic adsorption air purification and disinfection device is that electrostatic adsorption air purification and disinfection device generates high voltage electrostatic field by using discharge wire and negative plate. Under the action of high voltage generator, the electrostatic adsorption device can generate 4 kV~8 kV DC high voltage and form a strong electrostatic field inside the electrostatic adsorption device. When indoor air passes through an electrostatic adsorption device, particulate matter (including microorganisms) in the air is forced to be positively charged and then adsorbed onto the negative plate. The electrostatic adsorption device has a strong ability to capture particles with a diameter of 0.01 um.
1.2 The main categories of electrostatic adsorption air purification and disinfection devices are two kinds of electrostatic adsorption devices commonly used at home and abroad, namely two-stage plate electrostatic adsorption device and honeycomb electrostatic adsorption device. Two-stage plate electrostatic adsorption device is the most commonly used excellent electrostatic adsorption device in the world. Its advantages are not only improving the efficiency of bacteria removal and dust collection, but also easy to clean. At present, the two-stage electrostatic adsorption device is favored by domestic air purifier manufacturers. Its working principle is shown in Figure 1. Honeycomb electrostatic adsorption device is the most commonly used electrostatic adsorption device in domestic air purifier manufacturers. Its characteristics are that the process is relatively simple and the area of the negative plate is increased by using "honeycomb". The biggest shortcomings of honeycomb-mounted electrostatic adsorption devices are poor dust collection efficiency, difficulty in cleaning and the generation of more ozone.
2-Ion Air Purification and Disinfection Technology
Ion air purification and disinfection technology is mainly plasma air purification and disinfection device and negative ion air purification device.
2.1 Plasmas Air Purification and Disinfection Device
2.1.1 The concept of plasma: plasma is composed of a large number of charged positive and negative particles. When the positive and negative charges are equal, it is called plasma. Among them, photohydrogen plasma air purification and disinfection equipment is the most commonly used.
2.1.2 Operating Principle of Air Purification and Disinfection Device of Photohydrogen Plasma The Operating Principle of Air Purification and Disinfection Device of Photohydrogen Plasma is shown in Fig. 2. Under the irradiation of multi-band and specific wavelength light, on the one hand, the organic molecules in the air absorb photon energy of specific wavelength and undergo photosensitization process, and the organic molecules rapidly decompose into ions, free atoms, stimulated molecules or neutral molecules; on the other hand, the oxygen molecules in the air absorb photon energy of specific intensity and generate. Atomic oxygen, ground state oxygen and negative oxygen ions with strong chemical activity, and water molecules and hydrogen in the air produce hydroxyl radicals under the action of high-energy electrons and reactive oxygen species. When the specific light wave acts on the rare metal surface such as Ti and In, it will also produce decomposition and redox effect.

Under the action of these strong oxidizing atomic oxygen, ground state oxygen and hydroxyl radicals, not only the photosensitive decomposition of organic matter is rapidly oxidized to harmless and odorless gases such as water and carbon dioxide, but also the bacteria, viruses, fungi and other biological pollutants in the air are also killed by specific multi-band light irradiation. To remove harmful gases, deodorize, disinfect and sterilize, and clean air. Fig. 2 Working Principle of Photohydrogen Plasma Air Purification and Disinfection Device

2.2 Negative ion air purifier of negative ion air purifier: It is a kind of environmental optimizing appliance that uses negative ions produced by itself to purify, dust, deodorize and sterilize air. It is different from traditional air purifier in that it takes negative ions as the action factor to actively attack and capture harmful substances in the air. The concentration of negative oxygen ions will affect people's health, and the higher the concentration, the better for human health. According to environmental scientists, when the concentration of negative oxygen ions in the air is below 20 per cubic centimeter, people will feel tired and dizzy; when the number of negative oxygen ions in the air is between 10000 and 10000, people will feel calm and calm; when the number of negative oxygen ions in the air is 10 per cubic centimeter. When more than 1000, people will feel refreshed, comfortable and comfortable; when the number of negative oxygen ions in the air per cubic centimeter is more than 100,000, it can play a sedative, antiasthmatic, eliminating fatigue, regulating nerves and other preventive and therapeutic effects. Nowadays, with the increasing pollution, people need more negative ions. The negative ion air purifier can not only purify, dedust, deodorize and sterilize, but also provide a certain amount of negative oxygen ions, which can regulate staff's body and mind and prevent diseases. This technology has outstanding advantages and will be popularized in future engineering construction.
3 Photocatalyst Air Purification and Disinfection Technology
Photocatalyst air purification is a kind of purification technology that uses photocatalyst technology to degrade toxic and harmful substances in the air and kill many kinds of microorganisms by using hydroxyl radicals with strong oxidation ability after irradiation of certain energy level light in a specific situation.
4 Hospital Air Disinfection and Purification Technology
Comparing with other places besides operation department, hospital is also one of the important places of air pollution. In this special environment of hospital, there are many sources of pollution, many kinds of pathogenic microorganisms in the air, and many susceptible people in the hospital. It is the place where the virus spreads most directly and quickly, especially the outbreak of toxic respiratory tract infections. Handling public health emergencies. In recent years, new viral and bacterial respiratory infectious diseases continue to emerge. Respiratory diseases caused by various bacteria, viruses, fungi and so on are easily prevalent in large hospitals using central air conditioning. Once an epidemic occurs, air purification and disinfection in hospitals will be a serious challenge and crisis. Therefore, hospital air management is imperative. Among them, ultraviolet, ozone and ultraviolet circulating air are traditional disinfection and purification technologies. Because of their own shortcomings, they need to be used in special environment. With the rapid development of science and technology, photocatalyst, ion and electrostatic technology are gradually applied to indoor air purification projects. From Table 1, we can see that there are some shortcomings in air disinfection and purification technology in hospitals, but it is not difficult to find that their shortcomings can be solved by using two or three technologies simultaneously. For example, electrostatic technology has high efficiency in dust removal and sterilization, but low efficiency in odor removal in air. Ionic technology has high efficiency in sterilization, gas pollution removal and odor removal, but low efficiency in dust removal in air. If these two technologies are used simultaneously in engineering, indoor air quality can be comprehensively and effectively handled. In practical engineering, two or three complementary technologies are used to solve the problem of indoor air purification.
4.2 High Voltage Electrostatic Air Disinfection and Purification Products and Their Application Chemical and bactericidal functions. There are mainly the following products:

4.2.1 Independent Electronic Air Purification and Disinfection Machine
Independent electronic air purifying and disinfecting machine is a dual-function device for air disinfection and purification designed for professional medical indoors without purification.
4.2.2 Air Cabinet Type Electronic Air Purification and Disinfection Machine
Air cabinet type air purifying and disinfecting machine is installed in the mixed air section of central air conditioning unit and the front section of surface cooler. It is designed for purifying fresh air and return air entering the central air conditioning cabinet.
4.2.3 Air Channel Electronic Air Purification and Disinfection Machine
The air duct type air purifying and disinfecting machine is installed in the air supply pipeline of the circulating unit or fresh air unit, and is a purifying and dedusting, sterilizing and disinfecting equipment specially designed for the pipeline.
4.2.4 Fan-coil type electronic air purification and disinfection machine Fan-coil type air purification and disinfection machine is installed in fan-coil type central air conditioning return air outlet, is designed for purifying fan-coil unit return air purification and disinfection equipment.
4.3 Photohydrogen plasma air disinfection and purification products and their application Photohydrogen plasma air disinfection and purification products can remove all organic pollutants and kill pathogens and viruses due to the sporadic swimming of various oxidizing factors without leaving dead corners. There are mainly the following products:
4.3.1 Photohydrogen Plasma Air Purification and Disinfection Machine
Photohydrogen plasma air purification and disinfection machine is a professional purifying and sterilizing device installed in the central air-conditioning pipeline or the outlet pipeline to sterilize, remove gaseous pollutants and odor.
4.3.2 Independent Photohydrogen Plasma Air Purification and Disinfection Machine
Independent photohydrogen plasma air purification and disinfection machine is a special sterilization and deodorization air disinfection and disinfection machine designed and manufactured for public places or toilets with dense staff such as hospital halls and family members. Self-contained fan, independent operation, has strong adaptability and efficient treatment effect.
5 New Air Disinfection and Purification Technology
New air disinfection and purification technologies, such as photocatalyst, ion and electrostatic, have their own advantages and disadvantages as well as fiber filter material filters. New air disinfection and purification technologies, such as photocatalyst, ion and electrostatic, have the advantages of high efficiency, fast sterilization and disinfection, small wind resistance, simple maintenance, repeatable cleaning and long service life. The disadvantages are that the efficiency of dust removal is reduced due to surface dust, the price is higher, and the initial investment of the project is larger. The advantage of fiber filter material filter is that it will not reduce the filtration efficiency because of the long time used, but it will increase the resistance. When the final resistance is reached, it needs to be replaced. It can not be repeatedly cleaned and used, which will increase the operation cost of the project.
6 Summary
The application of new air disinfection and purification technology in engineering has been approved by users. It will inevitably promote the universal application of new technology in engineering, stimulate the mass production and improvement of new technology products in the market, and reduce the price, so that the advantages of new technology in engineering will be more prominent. With the continuous development of science and technology, the shortcomings of new technology will be solved and more advanced products will be developed, which will make medical purification project more energy-saving and reduce initial investment and operation costs. (Source: Clean Technology and Applications)