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There are physical methods, chemical methods and biological methods, but biological methods use biological factors to remove pathogens, the effect is slow, and the sterilization is not complete, and it is generally not used for disinfection of the source of infection, so the disinfection is mainly used by physical and chemical methods.

Physical disinfection

1. Mechanical disinfection should generally be brushed with soap and rinsed with running water, which can eliminate most or even all of the bacteria on the hands, and the use of multi-layer masks can prevent pathogens from being discharged or invaded from the respiratory tract. The use of ventilation filters can protect the air in operating rooms, laboratories and isolation rooms to protect the sterile state.

2. Thermal disinfection includes fire, boiling, flowing steam, high-heat steam, dry heat sterilization, etc. It can coagulate and denature pathogen proteins and lose normal metabolic function.

(1) This method can be used for burning pollutants with small economic value, metal instruments and corpses. Simple, economical and stable.

(2) This method is used for boiling resistant articles and general metal instruments, and disinfection is completed in 1~2 minutes at 100°C, but it takes a long time for spores. Bacillus anthracis spurs must be boiled for 30 minutes, tetanus spores for 3 hours, and botulinum toxin spores for 6 hours. For disinfection of metal instruments, alkaline agents such as 1~2% sodium carbonate or 0.5% soft soap can dissolve fat and enhance sterilization. Cotton fabric with 1% soapy water 15lkg, has the effect of disinfection and decontamination. When boiling and sterilizing, the volume should not exceed 34, and it should be immersed under the surface of water. Take care to leave gaps to facilitate convection.

(3) The flow steam disinfection has a relative humidity of 80~100% and a temperature of nearly 100 °C, and uses water vapor to condense on the surface of the object, release heat energy, and kill pathogens. And when the vapor condenses and contracts to produce negative pressure, it promotes the outer layer of hot vapor to enter the supplement, penetrates to the depth of the item, accelerates the heat, and promotes disinfection.

(4) High-pressure steam sterilization (moist heat sterilization) is usually 98.066kPa, the temperature is 121~126 °C, and it can completely kill bacterial spores in 15~20 minutes, which is suitable for heat-resistant and damp items.

(5) Dry heat sterilization has poor dry heat air conduction, small heat capacity, weak penetration, and slow heating of objects. It takes 160~170°C and 1~2 hours to sterilize. It is suitable for glass containers and metal instruments that cannot carry moisture.

Heat tolerance of different pathogens, expressed in heat death time. See attached table.

3. There are two types of radiation disinfection: non-ionizing radiation and ionizing radiation. The former has ultraviolet, infrared and microwave, and the latter includes a high-energy electron beam (cathode ray) of gamma rays. Infrared and microwave mainly rely on heat production for sterilization. Ionizing radiation equipment is expensive and harmful to items and the human body, so it is rarely used. The most common application is ultraviolet light, which can cause changes in cell composition, especially nucleic acids, plasma proteins and acids, leading to the death of microorganisms. The wavelength range of ultraviolet rays is 2100~3280A, and the wavelength of killing microorganisms is 2000~3000A, with the strongest effect of 2500~2650A. The tolerance to ultraviolet rays was the strongest in fungal spores, followed by bacterial spores, and bacterial propagules were the weakest, with a few exceptions. Ultraviolet rays have poor penetration, and those below 3000A cannot penetrate ordinary glass with a thickness of 2mm. The relative humidity of the air dust can reduce its bactericidal effect. Penetration of water decreases with depth and turbidity. However, because it is easy to use and has no damage to drugs, it is widely used for air and general surface disinfection. Irradiation can cause skin erythema, ultraviolet ophthalmia and ozone poisoning. Therefore, people should avoid or use corresponding protective measures when using.

Sunlight exposure also relies on ultraviolet light, but only 39% reaches the ground due to scattering and absorption in the atmosphere, so it is only suitable for microorganisms with low endurance and must be exposed for a long time.

In addition, in addition to laboratory applications, air filtration can be used in buildings with only ventilation, so it is difficult to apply general disinfection work.

(2) Chemical disinfection

According to the action on pathogenic proteins, they are divided into the following categories.

1. Coagulant protein disinfectants include phenols, acids and alcohols.

(1) Phenols mainly include phenol, lyso, hexachlorophenol, etc. It has a special odor and limited bactericidal power. It can discolor textiles, make rubber items brittle, and have a certain irritation to the skin, so there are fewer applications except for Laisu.

Phenol (carbolic acid): colorless crystals, with a special odor, pink when damp, but the disinfection power is not reduced. It is a cell plasma poison, which can kill the bacterial reproduction type 1:80~1:110 solution at 20 °C for 30 minutes, but cannot kill the spores and viruses with strong resistance. Adding soap can saponify fat, dissolve protein, promote its penetration, and strengthen the disinfection effect, but it is more toxic, irritating to the skin, and has a foul odor, so it cannot be used for skin disinfection.

Lysol (coal phenol soap liquid): Formulated with 47.5% cresol and potassium soap. Reddish-brown, soluble in water, decontamination, and the bactericidal power is 2~5 times stronger than that of carboxerol. It is commonly used as 2~5% aqueous solution, which can be used for spraying, wiping, soaking containers and hand washing. The bacterial propagation type can be killed in 10~15 minutes, and the effect on spores is poor.

Hexachlorophane: Bisphenol compound, slightly soluble in water, soluble in alcohol, ester, ether, alkali or soap can promote dissolution, less toxicity and irritation, but strong bactericidal power. It is mainly used for skin disinfection. Hand washing with 2.5~3% HCP soap can reduce skin bacteria by 80~90%, and it has been reported to cause nerve damage, so it is not suitable for long-term use.

(2) Acids have a killing effect on bacterial propagules and spores. However, it is easy to damage items, so it is generally not used for disinfection in the room. 5% hydrochloric acid can be used to disinfect washing utensils and fruits, add 15% salt to 2.5% solution to disinfect fur and leather, 10lkg heated at 30 °C and soaked for 40 hours. Lactic acid is often used for air disinfection, and 100m3 space can be fumigated with 10g of lactic acid for 30 minutes to kill staphylococci and influenza viruses.

(3) The concentration of 75% of ethanol (alcohol) can quickly kill bacterial reproduction, which has a slow effect on general viruses, uncertain effects on hepatitis viruses, and has a certain killing effect on fungal spores, but has no effect on spores. It is used for skin disinfection and thermometer immersion disinfection. Because it cannot kill spores, it cannot be used for soaking and disinfection of surgical instruments. Isopropylalcohol has a greater ability to kill bacteria than ethanol, and absorption through the lungs can lead to anesthesia, but it has no damage to the skin, and can be used instead of ethanol.

2. Dissolved protein disinfectants are mainly alkaline drugs, commonly used sodium hydroxide, lime, etc.

(1) Sodium hydroxide white crystal, soluble in water, strong bactericidal power, 2~4% solution can kill viruses and bacterial reproduction, 10% solution can kill Mycobacterium tuberculosis, 30% solution can kill spores in 10 minutes, because of strong corrosiveness, it is rarely used, only used to eliminate anthrax spores.

(2) Lime (CaO) can produce high temperature and dissolve protein when exposed to water, killing pathogens. 10~20% lime milk is commonly used to disinfect excrement, the dosage must be twice that of excrement, and it acts for 4~5 hours after stirring. 20% lime milk is used to disinfect anthrax contaminated places, sprayed every 4~6 hours, 2~3 times in a row. Brush the wall 2 times to kill Bacillus tuberculosis. Due to its unstable nature, it should be freshly prepared when applied.

3. Oxidizing protein disinfectants include chlorine-containing disinfectants and peroxide disinfectants. Because of its strong disinfection power, it is the most widely used in medical epidemic prevention work.

(1) Bleaching powder is the most widely used. The main ingredient is calcium hypochlorite [Ca(ClO)2, containing an effective 25~30%, which is unstable in nature and can be decomposed by light, heat, humidity and CO2. Therefore, it should be stored in a dark and dry place for no more than 1 year. The active ingredient hypochlorous acid can penetrate into the cell, oxidize the sulfide gene of cellular enzymes, and disrupt cytoplasmic metabolism. The sterilization power is strong and rapid in the acidic environment, and the high concentration can kill the spores, and the powder is used for the disinfection of feces, sputum, pus, etc. Add 200 grams of dry powder per liter, stir well, place 1~2 leaflets, add 5 grams of dry powder per liter of urine, and leave for 10 minutes. In addition to disinfecting excrement and secretions, 10~20% emulsion can be used to spray toilets, polluted vehicles, etc. If it is stored for a long time, the actual effective chlorine content should be measured and the preparation amount should be corrected. The powder and tablet of bleaching powder contain 60~70% available chlorine, and the amount can be reduced proportionally when used.

(2) ChloramineT is an organochlorine disinfectant, containing 24~26% available chlorine, which is relatively stable, kept closed for 1 year, and only loses 0.1% of available chlorine. Slightly soluble in water (12%), less irritating and corrosive, slower than hypochlorous acid. 0.2% 1 hour can kill bacterial reproduction, 5% 2 hours can kill Mycobacterium tuberculosis, and it takes more than 10 hours to kill spores. Various ammonium salts can promote its bactericidal effect. The 1~2.5% solution also has an effect on hepatitis virus. The active liquid must be prepared 1~2 hours before use, and if the time is too long, the sterilization effect will be reduced.

(3) Sodium dichloroisocyanurate (sod. dichlorisocynurate), also known as excellent chlorine, is a widely used organochlorine disinfectant, containing 60~64.5% chlorine. It has the advantages of high efficiency, broad spectrum, stability, high solubility and low toxicity. The aqueous solution can be used for spraying, soaking, and foaming, and can also be used with dry powder to directly disinfect pollutants and treat feces and other excrements, and the usage is the same as bleaching powder. Spray directly on the ground with a dose of 10~20gm2. Mixed with paraformaldehyde dry powder for ignition, the gas can be fumigated and disinfected, and can be mixed with No. 92 coagulant (hydroxyaluminum chloride-based iron powder, sulfuric acid, hydrogen peroxide, etc.) at 1:4 to become "clear in water" for drinking water disinfection. And it can be prepared with sodium sulfonate to make a variety of disinfectant washing liquids, such as Dijingmei, Youchlorojing, etc. It has a killing effect on hepatitis virus.

In addition, trisodium chloride phosphate and chlorobromodicyanuric acid have the same effect.

(4) Peroxyacetic acid (peroxy-aceticacid), also known as peroxyacetic acid, is a colorless transparent liquid, volatile and irritating sour, is a kind of same effect fast-acting disinfectant, soluble in organic solvents such as water and ethanol, with bleaching corrosive effect, volatile irritating sourness, is a high-efficiency and fast-acting disinfectant, soluble in organic solvents such as water and ethanol, with bleaching and corrosive effects, unstable, easy to decompose when exposed to heat, organic matter, heavy metal ions, strong alkalis, etc. 0.01~0.5%, 0.5~10 minutes can kill bacterial propagules, 1% 5 minutes can kill spores, the common concentration is 0.5~2%, can be disinfected by soaking, spraying, wiping and other methods, aerosol (5% concentration, 2.5mlm2) and fumigation (0.75~1.0gm3) disinfection under closed conditions.

(5) Hydrogen peroxide 3~6% solution, 10 minutes can be sterilized. 10~25% for 60 minutes, it can be sterilized, used for disinfection of heat-resistant plastic products, tableware, clothing, etc. 10% hydrogen peroxide deep glue spray disinfection indoor contaminated surface; 180~200mlm3, 30 minutes can kill bacterial propagules; 400mlm3, 60 minutes can kill spores.

Hydrogen peroxide vapor (HPV) disinfection technology is fast becoming the bio-decontamination method of choice for the pharmaceutical, biotechnology, and healthcare industries, achieving a 6-log kill rate of 6-log against the same biological indicator as the pressure cooker, Bacillus steatophilus. A wide range of disinfection products and services can be used to bio-decontaminate facilities during commissioning or shutdowns. Bioquell uses patented Clarus dual-cycle technology combined with PLC program control to optimize the effect of the sterilization cycle, when hydrogen peroxide forms a microcondensation on the surface of the room or cabin to achieve biological disinfection, this stage can be seen under the microscope a thin layer of hydrogen peroxide invisible to the naked eye, scientific research has confirmed that this low-temperature, residue-free process has begun to kill microorganisms during the steam generation stage. The formation of microcondensation ensures optimal conditions for microbial killing, with the shortest time (D-value) to reduce microorganisms by one log-level (1-log) when the condensation point is reached. A steep drop in the number of microorganisms can be seen from the sterilization kinetic curve, and with the formation of microcondensation, the number of biological indicators curve changes from soothing to sharply.

(6) Soaking in a concentration of 1~5% potassium for 15 minutes can kill bacterial propagules, and is often used for disinfection of eating utensils and melons and fruits.

4. Cationic surfactants mainly include quaternary ammonium salts, high concentration of coagulant protein, and low concentration inhibition of bacterial metabolism. It has the advantages of bactericidal concentration, low toxicity and irritation, no bleaching and corrosive effect, odorless, stable and good water solubility. However, the bactericidal power is not strong, especially the spor effect is not good, it is greatly affected by organic matter, and there are many contraindications for compatibility, which is its disadvantage. Domestic production has Xinjieer, disinfection Ning (Du Mi Cang) and disinfection net, with strong sterilization power, commonly used concentration of 0.5~1.0‰, which can be used for disinfection of skin, metal instruments, tableware, etc. It should not be used for disinfection of excreta and secretions.

5. Alkylated disinfectants

(1) Formalin is a 34~40% formaldehyde solution, which has a strong bactericidal effect. 1~3% solution can kill bacterial reproduction, 5% solution for 90 minutes or kill spores, indoor fumigation and disinfection generally use 20mlm3 plus the same amount of water for 10 hours, to eliminate spore pollution, it takes 80mlm324 hours, suitable for fur, man-made fibers, silk fabrics and other heat-resistant items. Because of its poor penetration and irritation, the disinfectant items should be spread out and the house should be sealed.

(2) Glutaraldehyde acts like formaldehyde. It is more stable in acidic solution, but the sterilization effect is poor, it can be maintained for 2 weeks in alkaline solution, but it strongly improves the sterilization effect, so usually 2% valerdehyde is added with 0.3% sodium bicarbonate, and the pH value is corrected to the compound (the sterilization effect is enhanced, and the stability can be maintained for 18 months. Non-corrosive, broad-spectrum, fast-acting, high heat, low toxicity and other advantages, can be widely used for bactericide, sporum and virus disinfection. It should not be used for skin and mucosal disinfection.

(3) Ethylene oxide (epoxyethane) is a colorless liquid at low temperature, with a boiling point of 10.8 °C, so it is a gas sterile at room temperature. Its function is to destroy the proteinization of microorganisms through alkylation. The general application is 0.4~0.7kgm2 at 15°C for 12~48 hours. When the temperature rises by 10°C, the sterilization power can be increased by more than 1 time, and the relative humidity of 30% has the best sterilization effect. It has the advantages of high activity, strong penetration, no damage to items, no residual poison, etc., and can be used for disinfection of paper, books, cloth, fur, plastics, man-made fibers and metal products. Due to its penetrating power, it needs to be sterilized in an airtight container. Avoid open flames to prevent explosion. Ventilation after disinfection prevents inhalation.

6. Miscellaneous

(1) Iodine interferes with protein metabolism through halogenation. The action is rapid and long-lasting, non-toxic, and less affected by organic matter. There are often iodine wine and iodophor (iodine and surfactant are amorphous conjugates). It is often used for skin and mucosal disinfection and emergency treatment of medical devices.

(2) Chlorhexidine (hibitane) is a biguanide compound. It has a strong disinfecting effect on bacteria. It can be used for disinfection of hands, skin, medical equipment, clothing, etc., with a common concentration of 0.2~1‰.