1, whether the cold air is discharged (the sterilizer should discharge the cold air before sterilization, usually 5 minutes);
2. Whether the sterilization temperature and pressure meet the requirements;
3. Whether the articles to be sterilized are placed too tightly (affecting the steam penetration, and when the articles to be sterilized need to be put into the container, such as culture medium, the plug should have air permeability, such as cotton balls, which cannot be sealed);
4, whether the pressure steam is maintained within the required range (automatic temperature control sterilizer can automatically maintain the set temperature, need manual operation, low temperature, poor sterilization effect, high temperature, serious loss of nutrients);
5, can use the method of sterilization exhaust, that is, after reaching the sterilization temperature and pressure, when closing the exhaust valve, don't close the exhaust valve, leave a small gap to continue the exhaust, let the cold air that has not been discharged continue to be discharged, and the condensate water and the exhaust valve are the same pipe.
The above contents are for reference only.
Ethylene oxide sterilization 2007-04-29 Source: China Packaging and Printing Exhibition Network According to literature records, in A.D. 1859, Woolz first discovered ethylene oxide (EO), also known as ethylene oxide or propylene oxide. But it is used as a disinfectant in 1936. In 1936, Schrade and Bossert found that ethylene oxide mixed with carbon dioxide was used to kill various pests and bacteria. In 1937, Gross and Dixon found that EO can kill 48 kinds of microorganisms. From 1940 to 1943, Griffith and Hull * * * published many books and applied for patents. From 65438 to 0949, Phillips and Kaye made a systematic and comprehensive study of EO. Since then, Ernst and Shull, Ernst and DoyleKereluk and Lloyd have made extensive and in-depth research on the sterilization mechanism, influencing factors, acute and chronic toxicity, sterilization effect, corrosiveness and its changes in the environment of ethylene oxide. Since 1950s, ethylene oxide has been used for hospital disinfection. According to the survey, in the mid-1990s, almost all medical institutions in the United States had EO sterilization equipment. Most hospitals in some big cities in China, such as Beijing, Shanghai and Guangzhou, have imported EO sterilizers. Because the latest EO sterilization equipment can provide very safe guarantee, EO will still be the most important low-temperature sterilization method in hospitals.
Physical and chemical properties of 1 ethylene oxide
EO is a simple epoxy compound with molecular formula of C2H4O and molecular weight of 44.05. EO liquid is colorless and transparent, with aromatic ether smell, and the threshold value of smell is 500 ~ 700 ppm, which means that if the surrounding environment smells EO, the air concentration is at least >: 500ppm, which is much higher than the maximum allowable exposure level of EO stipulated by NIOSH (Occupational Health and Occupational Disease Association) in the United States. EO is flammable and explosive, and its minimum combustion concentration is 3%(30000ppm). Inert gas is usually added to prevent EO from exploding and burning. EO has a specific gravity of 0.884 at 4℃, a boiling point of 10.7℃ and a density of10.52, so EO liquid can easily volatilize into gas at room temperature. Because EO is lighter than water, if it is directly discharged into water, a large amount of EO may overflow into the surrounding environment. Therefore, in general, the hospital's EO emissions are preferred to the atmosphere. EO can generate ethylene glycol when it meets water. The vapor pressure of EO is relatively high (Table 1), and the higher the vapor pressure, the stronger the penetration of articles. It is reported that EO can penetrate 0. 1mm thick polyethylene or polyvinyl chloride film in 5 minutes, 0.04mm thick nylon film in 22 minutes, 0.3mm thick neoprene cloth in 26 minutes and 0.39mm thick neoprene cloth in 4 1 minute. Because in order to fully achieve the sterilization effect of articles, fungicides must be able to fully contact all surfaces of articles (inside, outside, shallow and deep). This high permeability of ethylene oxide greatly improves its bactericidal effect.
Table 1 Vapor pressure of ethylene oxide at different temperatures
Temperature (℃) and steam pressure (mmHg)
-20.0
10.7
20.0
25.0
29.0
30.0
50.0 1.09
760.00
1094.00
1300.00
1500.00
1560.00
2967.00
Sterilization principle of 2 EO
EO can kill various microorganisms, including bacterial propagules, spores, viruses and fungal spores, and is a broad-spectrum disinfectant. It is generally believed that it can react with protein, DNA and RNA of microorganisms for non-2-specific alkylation. EO in aqueous solution can be alkylated with free carboxyl groups (COOH group (2NH2), sulfhydryl group (2SH) and hydroxyl group (2OH) on protein, replacing unstable hydrogen atoms to form compounds with hydroxyethyl group (CH2CH2OH), and the groups on protein are alkylated, which makes protein lose the reaction groups needed for basic metabolism, hinders the normal chemical reaction and metabolism of bacterial protein, and leads to microbial death. So far, all the data show that the bactericidal effect of EO is irreversible, that is to say, EO is a disinfectant rather than a bactericide. Moreover, according to various clinical and scientific research results, EO is the best chemical disinfectant among all chemical disinfectants or disinfectants. Ethylene oxide can inhibit the activities of some microbial enzymes, including phospholipase, peptidase, cholinesterase and cholinesterase. Ethylene oxide also alkylates with DNA and RNA, resulting in inactivation of microorganisms.
Advantages and disadvantages of 3 EO sterilization and its clinical application scope
3. The advantages of1EO (1) EO sterilization can be used to sterilize articles that are not resistant to high temperature and high humidity. (2) Ethylene oxide is considered as the best chemical sterilization agent, which can kill all microorganisms including bacterial spores. (3) It has strong penetrability, and can be used to sterilize various parts that are difficult to penetrate: for example, some thin and long catheters are difficult to achieve sterilization effect by other low-temperature sterilization methods, so EO or irradiation can only be used. (4) The damage to articles is small, because EO kills microorganisms through alkylation principle rather than oxidation process, so the damage to articles is small, and it is widely used for sterilization of heat-resistant precision instruments. (5) It can be wrapped with various packaging materials during sterilization, which is convenient for storage and transportation, and can be used after opening, thus avoiding the risk of cross-contamination. (6) There are standard chemical and biological monitoring methods, so as to effectively control the sterilization quality and find the packaging that failed sterilization in time. (7) have decades of experience.
3.2 Disadvantages of EO sterilization (1) Because it takes a long time to remove EO residues by ventilation, the whole sterilization cycle takes a long time. (2)EO is toxic and a suspected carcinogen, and the concentration of EO in indoor air must be controlled below the national standard. (3) Ethylene oxide is flammable and explosive, and shall not be leaked during storage and sterilization. In order to operate and store safely, a safe sterilizer must be selected.
3.3 Clinical Application Scope of EO EO has a wide range of clinical uses. The commonly used equipment and instruments for EO sterilization are: (1) rigid and soft endoscopes: arthroscope, bronchoscope, cystoscope, gastroscope, enteroscope, mediastinoscope, ophthalmoscope, otoscope, laryngoscope, prostatectomy, thoracoscope and urethroscope. (2) Medical equipment: anesthesia equipment, artificial kidney, diathermy equipment, wires, meter, heart-lung machine, breathing, treatment equipment and hemodialysis. (3) Instruments: electric drill, electrocautery, electrotome, dental drill, microsurgical instrument, nerve stimulator, manometer, surgical instrument, bone drill, needle and artificial joint. (4) Rubber products: catheters, dilators, drainage tubes, tracheal intubation, surgical gloves and sheets. (5) Plastic products: airway intubation, dilator, tracheal intubation gloves, pacemakers, heart valves, sprayers, Petri dishes and syringes. (6) Other books, toys, linear probes, probes, thermometers and stitches. Therefore, EO will be the most important low-temperature sterilization method in the past, future and future.
4 How to control the key parameters of ethylene oxide sterilization
The control of key parameters in ethylene oxide sterilization process is to ensure the sterilization quality. The key parameters of ethylene oxide sterilization are ethylene oxide concentration, humidity, temperature and time in the cavity during sterilization. These key factors directly affect the sterilization effect; The degree of each key factor can be different, but it must be balanced.
4. 1 time gas sterilization is not a fast process, and the sterilization time must be enough to kill microorganisms, and its length is affected by the following factors: the cleanliness of the sterilized items; Humidity and water content of microorganisms; Type and density of packaging materials used; The size of the package and the loading of sterilization load; Concentration of ethylene oxide; Temperature during sterilization; EO gas type, etc. The sterilization time of the items in the sterilization package varies with the manufacturing materials and packaging materials, and the sterilization time must ensure that the most difficult items in the load can also achieve sterilization effect. Under the same conditions, different loading methods and loads will also affect the sterilization time. The temperature and EO concentration of sterilizer will also affect the sterilization cycle time; The higher the temperature or EO concentration, the shorter the sterilization time; If the temperature is low, it needs longer sterilization time or higher EO concentration sterilization time, which is also affected by the pressure in the tank and EO gas circulation mode. Effective EO gas circulation contributes to the wetting and uniform heating of the pot. Different types of ethylene oxide gas have different sterilization time. The sterilization time of 100% pure EO gas is shorter than that of EO mixed gas. Sterilization time of sterilizers used in general hospitals varies from 1 to 5 hours. Generally speaking, the sterilization time of pure EO is shorter than that of EO mixed gas, and the length of time should be subject to the product manual of the sterilizer manufacturer.
4.2 When ethylene oxide is sterilized at temperature, the temperature will affect the killing rate of microorganisms. According to the calculation, the killing rate of spores will increase by 10℃ every time the temperature increases, and the temperature can increase the penetration of EO. Sterilizers used in hospitals are generally set at 49 ~ 60℃, and a small number of articles that cannot tolerate this temperature can choose 35 ~ 38℃, but at this time, EO concentration must be increased or sterilization time must be extended. Temperature drop in sterilization stage may lead to sterilization failure; According to AAMI requirements, the temperature error of sterilizer
4.3 EO concentration EO concentration is usually expressed in mg/L. The commonly used concentration of hospital sterilizers is 450 ~ 750 mg/L. At a certain temperature and relative humidity level, the EO concentration increases (from 50 ~ 500 mg/L), the microbial killing rate also increases significantly, and the sterilization time is correspondingly shortened as the EO concentration reaches the highest point. But EO concentration >; 500mg/L did not significantly improve the inactivation rate of microorganisms, and even reduced its inactivation rate, as shown in Table 2. In actual sterilization, considering the loss of EO, including the hydrolysis and adsorption of EO, the selected concentration should be higher than the highest relative concentration.
Table 2 Maximum concentration of ethylene oxide sterilization
Temperature (℃), relative humidity (%) and maximum relative concentration (mg/L)
25
30
35
4050
50
50
50900
Eight hundred
700
550
4.4 Relative Humidity The moisture content of sterilized articles, the drying environment of microorganisms and the relative humidity of sterilization environment are very important for EO sterilization. If EO concentration is 600mg/L, temperature is 54℃ and relative humidity is 40%, its ability to kill microorganisms is 0 10 times of relative humidity. The main reasons are as follows: (1) Water is a necessary reactant in the alkalization reaction. The reaction between water and EO opens its epoxy group and promotes its interaction with microorganisms. (2) Water promotes EO to permeate dry EO, and the permeability is greatly reduced. (3) Humidification can help to heat the sterilized object to a set temperature.
4.4. 1 Pre-wetted sterile materials must be pre-wetted. Generally, it is required that the sterilized materials be placed under the environmental conditions of 50% relative humidity for >: 2h; Step 2: Keep enough humidity in the pot to kill microorganisms. Many research data confirm that the ideal relative humidity for inactivating microorganisms is about 30%. However, in practice, the required relative humidity in EO tank is 40% ~ 80% to ensure sufficient power to push moisture into packaging and articles. However, it must be noted that there should be no water drops or too much moisture on the sterilized articles to avoid dilution and hydrolysis of ethylene oxide. The relative ratio of bacterial water content to sterilization environment water content also has obvious influence on the sterilization effect of ethylene oxide.
4.4.2 The lagging way of humidification is to add dehumidifier or wet towel in the cavity. Its main disadvantages are that the humidity level is difficult to control and articles cannot be heated. At present, the new humidification method is to automatically spray water vapor under negative pressure, which is also called humidification stage. >; 20 minutes. Its advantages are: uniform humidity; The humidity level is easy to control; You can heat things. The latest sterilizer introduced in the late 1990s is equipped with a humidity detector, which can directly monitor the relative humidity level in the pot. If the minimum relative humidity level cannot be reached, it will automatically stop sterilization and re-humidify. Temperature, time, concentration and humidity are the key parameters affecting the sterilization effect of ethylene oxide, but different from pressure steam and dry heat sterilization, there are ideal parameters to achieve sterilization effect, so it is difficult to specify the exact sterilization parameters.
5 requirements for ethylene oxide sterilization packaging materials
Packaging materials used for ethylene oxide sterilization should at least have the following characteristics: ethylene oxide sterilization agent must be allowed to enter; Can tolerate certain humidity; EO residue can be easily removed. Common ethylene oxide packaging materials are shown in Table 3.
Table 3 Ethylene oxide sterilization packaging materials
Qualified packaging materials unqualified packaging materials
Peel off the packaging bag
Teweiqiang
Polyethylene polyester film
Paper/polyethylene-polyester film
Paper/polypropylene-polyester film
Polyethylene plastic bag
wrapper
cloth
nonwoven fabrics
Paper coated or uncoated
Hard container
Plastic box covered with paper or Tyvek
All kinds of metal foil
cellophane paper
polyvinyl chloride
Impermeable polypropylene film
nylon
glass
Toxicity of 6 EO
6. 1 acute toxicity
6. 1. 1 Clinical manifestations Inhalation of EO in large quantities can cause respiratory irritation, dizziness, fatigue, nausea and vomiting (immediately or afterwards), chest pain and neurotoxic reaction. Liquid EO can cause skin irritation, dermatitis and blisters. Eye contact with EO will cause serious eye injury, and high concentration gas splashing will cause serious eye irritation and injury. Exposure to ethylene oxide in digestive tract is an uncommon route of exposure. Liquid EO enters the digestive tract, which is corrosive and can cause serious irritation and burns to the mucosa of the digestive tract.
6. 1.2 Emergency handling
After excessive exposure to EO, quickly remove the patient from the poisoning site, inhale fresh air immediately, and seek medical attention as soon as possible. After skin contact, wash the contact area with water > 15min, take off dirty clothes at the same time, wash the contaminated area with water and soap, and seek medical attention as soon as possible. Eye contact with liquid ethylene oxide or high concentration ethylene oxide gas for at least 10 minutes, and seek medical attention immediately. After touching the digestive tract, inform the doctor or the toxicity control center as soon as possible, drink 1 ~ 2 glasses of water, and touch the back of the throat with your hands to cause vomiting; Coma people can't cause vomiting or feed anything.
6.2 Chronic toxicity
6.3 regarding the chronic toxicity of EO to human beings, Joyner( 1964) investigated 1 a factory producing EO, and the average length of service of the workers surveyed was >: 10 year, and the concentration of EO in the air of the workshop was 5 ~ 10 ppm. No obvious abnormality was found, and no evidence of chronic poisoning was found in the laboratory results. In 1980s, NIOSH (National Institute of Occupational Health and Occupational Diseases) analyzed the causes of death of 18254 workers who were exposed to ethylene oxide in four factories nationwide. During this period, TWA (8-hour average time-weighted concentration) of EO in the working environment was 4ppm. The results show that the mortality of other tumors and other chronic diseases is normal except leukemia and lymphoma, but there is no evidence to prove the mortality of leukemia and lymphoma. However, NIOSH( 1989) still regards EO as a suspected carcinogen, which may have reproductive toxicity and neurotoxicity. In 1984, NIOSH specified TWA and PEL (allowable exposure level) in view of EO being a suspected carcinogen.
7 EO emissions and environmental control
7. 1 EO safety protection principle EO is a flammable and explosive chemical. When the concentration in the air is >: 3%, an explosion will occur, and the following safety principles must be observed during operation () Ensure that the sterilizer and gas cylinder (or gas cylinder) are far away from matches and other kindling: 1EO, lighted cigarette butts, sparks and static electricity. (2)EO gas cylinders or gas tanks shall be handled in strict accordance with the storage requirements of inflammable and explosive articles stipulated by the state. (3) The concentration of air in EO sterilization environment should be. () Dealing with employee EO
7.2 EO sterilizer installation requires EO to be flammable, explosive and toxic, so EO sterilizer must be placed in a well-ventilated place, and it should be avoided to be installed in a place with poor ventilation and too small space; Do not put EO tank or gas tank near the fire source, and try to stay away from the main passage. In order to facilitate future maintenance and regular maintenance, a space of 5 1cm should be reserved above each side (including) of the EO tank. The ventilation system in the room should not be recycled, and the indoor air exchange frequency should be at least > 10. The EO sterilizer should be equipped with a special exhaust pipe, and the air entering the room should be safely isolated from other exhaust pipes in the building. Must be able to flow through the sterilization and EO sterilizer and then discharged to the outside, as far as possible without dead ends. Lounge and storage room should be far away from sterilizer and gas cylinder (gas cylinder storage place). EO sterilizer does not need to be installed in a special room if there is proper space and local exhaust system. The ventilation system shall include: (1) indoor air exchange at least > every hour; 10 times, and ensure that the sterilization area is under negative pressure (relative to other working areas). (2) Special EO exhaust pipe system. (3) Reasonable air flow mode. (4) Local exhaust hood.
7.3 EO Emissions Regarding EO emissions, in 1994, the US EPA has clear emission regulations for commercial sterilization, but not for hospitals. As an explosion-proof agent, CFC can prevent EO explosion. However, due to the destruction of the ozone layer by CFCs, 22 countries including China and the United States signed the Montreal Convention in 1987, and gradually banned the use of CFCs. The United States and other developed countries banned the use of CFCs on June 5438+0.996+0. 1, and China also made clear the timetable for banning the use of CFCs.
7.3. 1 Installation requires that the hospital's ethylene oxide be discharged from the atmosphere first. When installing, it is required (1) to have a special exhaust pipe system. (2) The exhaust pipe material must be EO impermeable, such as copper pipe. (3) There shall be no combustible substances or air inlets of buildings, such as doors, fresh air outlets and open windows, within 7.6m of the exhaust port of the exhaust pipe. (4) If the length of the vertical part of the exhaust pipe is >: 3m, a water collector must be installed, so as not to make the exhaust pipe droop or circle, causing water vapor accumulation or freezing in winter and blocking the pipeline. (5) The exhaust pipe should be led to the top of the floor, and reverse downward at the exit to prevent water vapor from staying on the pipe wall or blocking the pipe wall. (6) Professional installation engineers must be hired to install EO sterilizers according to the requirements of manufacturers.
method of erection
If it can only be discharged into water, EO will overflow due to air cracks in most drainage pipes. The hot air of the sterilizer will also generate upward airflow, pushing EO to be discharged upward. Therefore, it is absolutely necessary to ensure that EO gas will not flow back into the working environment. The following methods can be adopted: (1) EO collection box can be installed outside the exhaust port of EO sterilizer to immediately remove EO vapor. EO collection box should surround all open sewers, and the whole sewer system must be closed. (2) A liquid/gas separator can be installed, and the liquid can be directly discharged into the sewer, and the gas can be discharged according to the above method. (3) This exhaust mode must be installed in a well-ventilated, preferably unmanned factory building, and the exhaust port has negative pressure. Detoxification method If conditions permit, EO can be detoxified and discharged. For EO industrial sterilization, detoxification is necessary, while hospital sterilization can be directly discharged into the atmosphere without special regulations (the amount of EO used in hospitals is very small). Generally, the following detoxification methods can be adopted: (1) adding catalyst to decompose EO into carbon dioxide and water, and then directly discharging it into the atmosphere. This method is especially suitable for hospitals. (2) The absorbent absorbs EO, and can only handle a small amount of EO, which can be used for fume hoods or temporary discharge. (3) Adding acid for hydrolysis, EO can be decomposed into ethylene glycol and carbon dioxide by concentrated sulfuric acid, which is mainly used in industry. (4) The recycling is mainly used for industrial sterilization, and the investment is large.
8 ethylene oxide residue
EO residue mainly refers to EO remaining in articles and packaging materials after EO sterilization, and its two by-products ECH (chloroethanol ethane) and EG (ethylene glycol ethane). Exposure to excessive EO residues (especially grafts) can lead to burns and irritation, hemolysis, cell destruction and so on. Residues affecting EO are related to the following factors.
8. 1 material type
8.2 PVC and polyurethane absorb more EO and need longer ventilation time. The amount of EO absorbed by PTFE and nylon is very low, but they are closely combined and need a long ventilation time. Polyethylene and polypropylene have moderate absorption capacity, but they are easy to release when ventilated. Metal and glass do not absorb EO at all and can be used directly without ventilation, as shown in Table 4.
Table 4 Minimum ventilation time of various articles under different conditions (h)
Materials Indoor air (℃) mechanical ventilation (50℃) fume hood (60℃)
Metal and glass
No package.
parcel
External rubber
External polyethylene and polypropylene
Polyvinyl chloride other than plastic
polyvinyl chloride
plastic
Implantable pacemaker
2
24
48
96(4d)
168(7d)
168(7d)
04(2 1d)
Can be used immediately.
2
eight
12
12
12
12
32
2
five
eight
eight
eight
eight
24
Note: 3 No plastic packaging; Packaging with plastic or contacting with human tissues.
8.2 Physical parameters
The thicker the same material, the more difficult it is to discharge the residue. For example, the residual speed of 0.8mm plastic row is 3 times that of 1.6mm plastic; The same material, the same weight, the larger the surface area, the easier it is to discharge the residue. Polymer density also affects the absorption and emission of EO. The higher the density, the lower the absorption, but the combination is tight and difficult to discharge. While the low density absorbs more and is easier to discharge.
8.3 Packaging, loading and loading capacity The greater the loading capacity, the denser the loading and the tighter the packaging, the more difficult it is to discharge.
8.4 Sterilization and ventilation parameters The higher the temperature during ventilation, the shorter the time required.
8.5 The use of sterile articles, such as grafts, requires a long ventilation time. Compared with natural ventilation, mechanical ventilation can provide great security, and it takes less time and does not pollute the working environment. Therefore, EO sterilization in American hospitals does not allow natural ventilation. American AAMI standards for mechanical ventilation are: 60℃, ventilation for 8 hours; 50℃, ventilation12h; 38℃, ventilated for 32 ~ 36h. For some special items such as implants, it may be necessary to extend the ventilation time. AAMI in the United States classified the articles into three categories according to the time of use, and established the maximum residue standards according to different classifications, as shown in Table 5. Relevant residue standards in other countries: The maximum EO residue in French Pharmacopoeia is 2ppm. No EO residue was found in German health institutions, and the sensitivity of the detection method was at least 1ppm. According to China's national standards, EO remains when disposable medical supplies are sterilized by EO bacteria or leave the factory.
Table 5 Maximum allowable values of ethylene oxide and its harmful compounds in the United States (ppm)
Instrument name EOECHEG
intrauterine contraceptive device
contact lens/contact lenses
Instruments in contact with mucosa
Instruments in contact with blood (in vitro)
Instrument in contact with skin
Implant in vivo (>:100g)
Implant in vivo (10 ~100g)
In vivo implant (
25
250
25
250
250
100
25 10
25
250
25
250
250
100
25 10
500
5000
250
5000
5000
2000
500
table
Nine types of ethylene oxide sterilizers
EO sterilizers used in hospitals are divided into two types: mixed gas type 100% pure EO type. Generally speaking, a modern automatic ethylene oxide sterilizer must be able to control the quality of four basic parameters to avoid the failure of ethylene oxide sterilization and ensure high safety. The exposure time of (1) to EO gas generally varies from 18h (the sterilization time of mixed gas is longer). (2) In general, the sterilization temperature is 49 ~ 60℃ for hot cycle and 35 ~ 37.8℃ for cold cycle. (3) the gas concentration range is 450 ~1200mg/L. (4) the humidity range in the cavity is 30% to 70% RH. Therefore, when purchasing EO sterilizer, we must fully understand how EO sterilizer controls these key parameters, such as whether the parameters can not reach the standard sterilization and whether there is termination function.
Characteristics of 10 ethylene oxide sterilizer
EO sterilizer must have the following features in design to ensure its safety: (1) Automatic door lock closing: after EO gas is released, the boiler door must be automatically closed and opened. If it is necessary to forcibly stop the circulation, the tank can only be opened after EO gas is discharged. (2) The door is well sealed: EO gas is easy to leak during positive pressure sterilization. (3) Groove gasket: It can not only ensure that the special sealing performance of the door is not easy to be damaged when it is opened or closed, but also ensure the integrity of the seal. (4) Final vacuum and pulse washing: After sterilization, final vacuum and pulse washing can effectively remove E residue. (5) Can give an alarm: once the machine fails, including EO leakage, it can give an alarm loudly in time. (6) Automatic exhaust: In case of power failure and other obstacles, EO in the pot can be automatically exhausted. (7) The sterilizer has dual functions of sterilization and ventilation: after sterilization, it directly enters the ventilation stage, and the ventilated articles can be used directly.
10. 1 mixed gas ethylene oxide sterilizer
EO is a flammable and explosive gas. In order to prevent EO from burning and exploding, explosion-proof agents such as CO2 (8.5% EO 9 1.5% CO2) and CFC (88% CFC, 12% EO) are often added. Due to the cessation of CFC use, HCFC(8.6%EO, 9 1.4%HCFC) was used to temporarily replace CFC in foreign countries (the United States EP stipulated that HCFC would be banned in 2030). Domestic production of HCFC is still in the process, and the price of HCFC is relatively expensive. At present, only CO2 can be used as the bonding gas. As a mixed gas, CO2 has the advantages of no harm to the environment and moderate price, but the disadvantage is that (1) two mixed gases (EO and CO2) will be stratified, especially when the pressure is insufficient, which may affect the sterilization quality. Promote EO to form polymer and block the pipeline. (3) During sterilization, the pressure in the cavity is high, which may easily cause the articles to be broken. (4) Due to insufficient pressure, only 50% of each bottle of gas can be used. (5) The mixed gas is supplied from the steel cylinder to the tank through the pipeline, and attention should be paid to the possibility of any leakage at the pipeline valve. (6) The whole sterilization stage is a positive pressure process. (7) Long sterilization time.
10.2 100% pure ethylene oxide gas sterilizer
100% pure EO gas mainly uses small-dose gas tanks (for example, at present, the gas per tank is less than 100 ~ 200 g at most) to reduce the risk of EO explosion and leakage. 100% pure EO sterilizer has the following characteristics: (1) No external pipeline is needed, and the EO gas tank is put into the cavity and automatically punctured to release EO gas. (2) the sterilization time is short. (3) The whole sterilization process is negative pressure sterilization, which is not easy to leak. (4) Pay attention to safety when storing the gasholder to prevent leakage and explosion. At present, pure sterilization pots are more and more accepted by hospitals.