Sterilization with saturated steam under pressure - autoclaving. What is pressure steam sterilization (autoclaving)? Operating mode of the oven
General rules. Sterilization with steam (damp heat) is carried out in an autoclave with saturated steam under pressure, usually for 15-20 minutes at a temperature of 121 ° C. When the vapor pressure rises, its temperature rises (Table 6).
Table 6
Saturated steam temperature at different pressures
* Currently, pressure is usually expressed in pascals, 1 atm ( physical atmosphere) = 1.01325 10 5 Pa - 10 2 kPa.
Control temperature regime in an autoclave is possible with the help of substances having a certain melting point. They are placed in an autoclave in test tubes with the addition of paint (benzonaphthol, melting point (t^) 110 °С, benzoic acid, / pl 120 °С).
Particular attention should be paid to the sterilization of culture media. The autoclaving mode, which in this case is the most common and effective method, should not change the properties of the medium (Table 7).
Table 7
Sterilization mode of various media by autoclaving
As a rule, it is considered that at pressure, atm; 0.5; 1.0; 1.5; 2.0 achieved certain temperature, °С; 115, 120, 127, 133 respectively. Up to 2 atm, the pressure is increased when the material is heavily clogged with temperature-resistant forms of microorganisms. The duration of sterilization depends on the composition of the object to be sterilized and the degree of its bacterial contamination and ranges from 30 minutes to 1-1.5 hours.
The effectiveness of sterilization is checked by inoculation of material known to be infected with spores on nutrient media. The material is kept in the autoclave together with the objects to be sterilized.
Most autoclaves are gravitational: steam moves in them from top to bottom under the influence of the difference in air and steam densities. Very important proper preparation samples to be sterilized and appropriate loading of the autoclave.
The most convenient are automatic autoclaves equipped with time sensors and automatic temperature controllers. Laboratory autoclaves must have operating mode sensors on the thermometer scales. Sample packs should be placed freely in relation to each other so as not to impede the penetration of steam.
Depending on the volume of liquid and the number of containers in the load, the duration of sterilization changes (Table 8). It is smaller for small volumes. Thus, it is possible to choose the duration of sterilization cycles according to the size and number of containers.
Table 8
Influence of liquid volume and number of containers on the time required to reach a temperature of 121 °C in an autoclave
At the end of the sterilization cycle, it is necessary to slowly reduce the pressure, strictly observing the cooling time of the sterilized nutrient medium. Before opening the autoclave, it is necessary to make sure that the pressure has been established in it. environment shown on the manometer. If the lid of the autoclave is opened prematurely (before the pressure drops), air can be drawn in, contamination of the solution, boiling of liquid in vessels or flasks and pushing plugs out of them. When sterilizing flasks and bottles, caps should be loosely closed to allow ventilation and prevent glass breakage.
Nutrient media containing carbohydrates are sterilized in an autoclave at reduced pressure (0.5 atm) and a temperature of 110-112 ° C for 10-15 - 20 minutes, counting the time from the moment the desired pressure is reached.
The media are poured no higher than half the height of the vessel (Table 9), cotton plugs should be sufficiently dense, wrapped with gauze, but not with cellophane. On top of the cork, the neck of the flask is covered with newspaper or parchment and fixed with threads.
Table 9
Filling level various types flasks with liquids
Autoclaving is carried out by a specially trained specialist, since the maintenance of a pressure apparatus requires training and strict adherence to safety regulations.
B. To sterilize heat-labile materials (for example, complex nutrient media), use fractional sterilization with flowing steam when the autoclave door is not tightly closed. It involves a 3-4-fold repetition of the following cycle: the material is treated for 30-60 minutes with fluid steam in an autoclave at a temperature of 100 0 C or kept in a water bath at 80 0 C, then placed in a thermostat at 37 0 C for a day. in the thermostat, bacterial spores that did not have time to die germinate into vegetative forms, which die during the next treatment cycle.
Tyndallization- a milder version of fractional sterilization, used to sterilize even more heat-labile objects. At the same time, the object to be sterilized is kept at a temperature of 56–60 0 C for 5–6 days in a row, in between they are placed in a thermostat for spore germination.
Tyndallization/fractional sterilization is not effective against prions.
Disadvantages of steam sterilization associated with the fact that the steam turns into condensate, which corrodes the metal of the instruments, and also moistens the materials with the risk of reinfection.
Air way. Sterilization with dry hot air is carried out in metal dry-heat cabinets (“dry heats”) (Fig. 68). Sterilization modes include temperature and time (Table 25).
Rice. 68. Dry fat sterilizer
Table 25
Dry heat sterilization modes
Dry hot air does not moisten the products, and therefore does not cause corrosion of the metal of the tools.
Disadvantages of the air sterilization method linked to physical properties dry hot air:
causes drying of bacterial cells, as a result, the rate of their death slows down;
sterilization efficiency is reduced if, due to improper loading of instruments, air gaps are formed in which the temperature is lower (thermal conductivity of air is less than steam). Therefore, dry ovens are equipped with internal fans for forced circulation air;
during prolonged exposure, it can cause charring of sterilized materials, therefore, dry heat sterilization is used for products made of thermostable materials (glass, metal), as well as for hydrophobic substances (oils).
5. Glasperlen method (glass beads) is designed for rapid sterilization of all-metal instruments that do not have cavities, channels and locking parts (Fig. 69).
The Glasperlen method is used in dentistry for express sterilization of small instruments (burs, pulp extractors, root needles), as well as the working parts of larger instruments (probes, trowels, spatulas). You can also sterilize acupuncture needles. Glasperlen sterilizer can be in working order during the day. Sterilizable instruments do not dull or rust.
The Glasperlen method is used to sterilize dental instruments. European countries and Israel since 1997. However, it is not approved in the USA, since with glasperlene sterilization the instrument is not completely sterilized, but only its work zone. It can only be used in conjunction with chemical sterilization.
Disadvantages of the Glasperlen method:
Glasperlene sterilization is not a complete sterilization method. It is possible to sterilize only small, all-metal instruments that are completely located in the environment of heated glass beads. When sterilizing large instruments, only the working part can be placed in the sterilizing environment. Manufacturers of foreign glasperlenic sterilizers often indicate unjustifiably a short time shutter speeds: 5–15 sec. At the same time, experimental data indicate that even with a holding time of 180 seconds, sterilization of tongs, scissors and other instruments with massive locking parts is not ensured;
Instruments can only be sterilized unpackaged. Instruments sterilized in a glasperlene sterilizer should not be stored;
There are no chemical means of controlling the operation of glasperlene sterilizers.
6. Ultraviolet radiation with a wavelength of 260 nm is used to sterilize room air (in operating rooms, boxes), and liquids (milk, juices, water). The source of UV radiation are bactericidal and quartz lamps. Exposure to UV rays should be direct, as they have a weak penetrating ability and do not pass through ordinary glass, white paper. Long work lamp reduces the intensity of radiation, so it is advisable to conduct irradiation intermittently. Irradiation period 30–60 min. UV rays can cause swelling of the mucous membrane of the eyes, so you should not be in a room with lamps on.
7. Radiation method . The sterilizing agent in radiation sterilization is - and β-radiation. The most widely used is radiation, which has a high penetrating power (usually the cobalt-60 isotope, less often the cesium-137 isotope). β-emitting isotopes are used extremely rarely, since β-radiation has a much lower penetrating power.
The effectiveness of radiation sterilization depends on the total radiation dose and does not depend on time. The mean lethal dose for microorganisms is always the same, whether irradiation is carried out at low intensity for a long period of time or briefly at high radiation intensity. A dose of 25 kGy (2.5 Mrad) reliably guarantees the destruction of highly resistant spore forms of microorganisms. The temperature of the items to be sterilized does not rise during sterilization.
The radiation method is used for highly efficient industrial sterilization of products that cannot withstand high temperatures: disposable products from polymeric materials (syringes, droppers, catheters), cutting tools, suture and dressing material, some drugs. Large batches of packaged materials can be sterilized. The sterilization process is automated.
In healthcare facilities, radiation sterilization is not used due to the high cost of installations and for safety reasons.
8.Infrared radiation creates a temperature of 200 ± 30 0 C in the working chamber of a small-sized sterilizer. Full cycle Sterilizing unwrapped instruments in an infrared sterilizer takes 10 to 25 minutes (depending on instruments), including the warm-up and cool-down steps.
Disadvantages of infrared sterilization:
inability to sterilize packed instruments;
Limited acceptability due to damaging effect on polymer materials(plastic, rubber, etc.);
There are no chemical means of controlling the operation of infrared sterilizers.
9. Exposure to high-frequency ultrasound leads to the formation of foam from the smallest gas bubbles that are in a dissolved state in the CP of the cell. This leads to rupture of the COP and the death of microorganisms. Juices are sterilized by ultrasound.
Chemical methods of sterilization
Chemicals are used for low-temperature sterilization of large items, as well as heat-sensitive materials and equipment, which become unusable with other sterilization methods.
1. Gas method it is used for sterilization of large-sized products, as well as heat-labile medical equipment and rubber and plastic products (endoscopes and accessories, dialyzers, catheters). Chemical compounds are used that have an unconditional sporicidal effect: ethylene oxide, methyl bromide, a mixture of ethylene oxide and methyl bromide . In gas sterilization, temperature, humidity, sterilizing gas concentration, pressure and exposure must be strictly controlled. This is only possible if there is equipment with automatic cycle passage.
Ethylene oxide used to sterilize objects sensitive to temperatures above 60 0 C. Ethylene oxide requires more time to sterilize than heat treatment. Typically, ethylene oxide sterilization is carried out for three hours at 30–60 0 C and relative humidity above 30%, the gas concentration in this case is 200–800 mg/l. Ethylene oxide is highly flammable.
Disadvantage of gas sterilization is that gases can enter into chemical reaction with product materials, forming toxic and carcinogenic compounds. Therefore, after gas sterilization, degassing is necessary - removal of residues of the applied agent from sterile products in special aerators within 2 hours.
2. Liquid sterilization with solutions of chemical compounds (sterilants) is used for sterilization of thermolabile medical instruments, suture material, gloves, optical instruments, for storage of needles, tools.
at room temperature: oxygen-containing (6-90% hydrogen peroxide) and chlorine-containing ("Dezokson-1"), 96% ethyl alcohol;
at elevated (up to 40–50 0 C) temperature: aldehydes (2% glutaraldehyde, formaldehyde, 0.55% orthophthalaldehyde).
Sterilization with solutions chemical compounds is carried out in sterile containers made of glass, metals, heat-resistant plastics with the products completely immersed in the solution with their free layout. To avoid dilution working solutions used for sterilization, the products immersed in them must be dry.
35 –90% hydrogen peroxide used to sterilize heat and temperature sensitive items such as rigid endoscopes. Most great advantage hydrogen peroxide as a sterilant - short cycle time: the use of high concentrations of hydrogen peroxide can reduce the sterilization cycle time in modern installations to 28 minutes. Hydrogen peroxide can be mixed with formic acid in endoscope sterilizers.
However, not all objects can be sterilized with hydrogen peroxide and its penetrating power is lower than that of ethylene oxide.
Aldehydes. Sterilization with formaldehyde is carried out at a temperature of 60–80 0 C for 60 minutes. Many vaccines are sterilized with formaldehyde. Formaldehyde cannot be used for sterilization optical instruments, endoscopic equipment, implants.
0.2% acetic acid used to sterilize instruments.
0.01% sodium merthiolate used for the preservation of sera and liquid vaccines.
BUTantibiotics added to nutrient media during virological and immunological studies.
silver ions have a toxic effect on some bacteria, viruses, algae and fungi due to the oligodynamic action of silver. However, testing and standardizing this stripping method is difficult.
Prions are highly resistant to chemical sterilization. Chlorine and sodium hydroxide are the most effective against prions.
Disadvantages of sterilization with solutions of chemical compounds:
it is necessary to prepare for sterilization in the same way as for work in the operating room (sterile gown, gloves, shoe covers, mask). The room should be equipped as a bacteriological box;
at the end of the process, it is necessary to neutralize the sterilizing solution with sterile distilled water;
chemicals often have a short shelf life, cause corrosion of tools; it is necessary to use substances that are chemically compatible with the processed objects;
inability to sterilize packaged products;
the difficulty of monitoring the effectiveness of processing;
The use of chemical sterilants creates new problems for occupational safety: many chemical sterilants are volatile and toxic when in contact with skin and mucous membranes.
Therefore solutions chemicals it is advisable to use for sterilization only in cases where the use of other approved methods of sterilization is not possible.
Of interest is the technology sterilization using electrochemically activated solutions (anolytes), produced in special installations.
Advantages electrochemically activated solutions lie in the fact that in the presence of electricity, these funds can be obtained directly in the medical facility from drinking water and table salt. "Neutral anolyte" is recommended for sterilization of endoscopes when room temperature within 45 minutes.
disadvantage of these funds is a damaging effect on products made of corrosion-resistant metals.
3. Plasma sterilization. Plasma - decomposition products of hydrogen peroxide, formed under the influence of electromagnetic radiation.
Plasma sterilization is carried out at a temperature of 46-50 0 C for 54-72 minutes. Plasma sterilizers can be used in both centralized and decentralized sterilization organization systems. The smallest plasma sterilizer occupies an area of 1 m 2, the volume of its working chamber is 50 liters.
Hydrogen peroxide decomposes into non-toxic products - water and oxygen, without any harmful effects on humans and the environment.
Disadvantages of plasma sterilization:
products made of cellulose, polyamide, rubber, powders, liquids, surgical linen, dressings are not subject to plasma sterilization;
an inaccessible method for widespread use in medical facilities due to the high cost of equipment. The use of the plasma method is most suitable for sterilizing unique heat-labile products that are available in a single copy and are used repeatedly during the working day. For everyday routine sterilization, it is worth choosing a more accessible and cheaper method;
there are no universally recognized international standards for this method.
4. Ozone sterilization. Ozone is a strong oxidizing agent. Ozone has been used for many years in industrial facilities for sterilization of drinking water and air, as well as for disinfection of surfaces. It has recently been proposed for sterilization in medicine. Sterilization is carried out in special devices with an ozone-air mixture produced by an ozone generator from atmospheric air.
Disadvantages of ozone sterilization:
The oxidizing power of ozone limits its range of applications. Upon contact with ozone, products made of steel, copper, rubber can be damaged;
ozone is toxic, and the devices available today do not allow to protect personnel from contact with it;
ozone is unstable;
the development of sterilization modes in relation to specific products turned out to be problematic due to the limitations in the capabilities of the created models of devices.
Mechanical sterilization
Mechanical sterilization (filtration) involves passing the material to be sterilized through filters, mechanical retention of microorganism cells and their adsorption in the pores of the filter.
Filters with a pore size of 0.2 microns effectively trap bacteria. Viruses can also be retained if the filter has a pore size of 20 nm. Prions cannot be removed by filtration. Filters are made from finely porous materials (kaolin, asbestos, porcelain, nitrocellulose). They are placed in a special filter holder, and then the sterilized solution is passed under pressure. With a high degree of contamination, filters with different pore sizes (from large to small) are successively used, and during filtration, microorganisms of various sizes are gradually “screened out”. Filtration is used to obtain a small amount of sterile solutions.
Can be sterilized by filtration thermolabile liquids (medications; nutrient media containing proteins and vitamins) and air(during immunological and virological studies). For achievement best results sterilization of fluids by filtration is carried out in laminar flow hoods, in which the air is also filtered.
(autoclaving)~ most effective method sterilization (temperature above 100 X). It is carried out in a special autoclave apparatus. The principle of sterilization is based on the fact that pure saturated water vapor at high pressure, condensing, raises the temperature inside the boiler (autoclave). The reduction in the volume of steam after condensation contributes to its penetration into the interior of the object to be sterilized.
Vertical autoclave (Fig. 29, BUT) It is a cylindrical double-walled metal cauldron with a hermetically sealed lid on top. Through a special tap with a funnel between the walls, water is poured to a certain level. The inner wall of the boiler in the upper part has holes, in the lower part of the boiler there is a tap through which, when the water is heated, the steam displaces air from the autoclave boiler. A metal protective frame is put on top of the autoclave, and there should be free space between it and the autoclave itself. The autoclave is heated with electricity. After loading the autoclave, the lid and the tap through which water is poured are closed, the lower tap temporarily remains open. The heated water between the walls of the autoclave boils, the resulting steam rises
Rice. 28. Electrical water bath:
I- frame; 2 - thermometer-regulator; 3 - lid; 4- Control Panel
and passes through the upper openings of the inner wall into the interior of the boiler, pushing the air out through the bottom open tap. When all the air is forced out and the steam begins to come out in an even stream, the lower tap is closed. As a result, the steam pressure inside the autoclave rises. The beginning of sterilization is considered the moment the pressure gauge reaches the specified value. Heating is regulated throughout the sterilization, maintaining the pressure at the same level. In case of excessive pressure, the autoclave is provided safety valve through which excess steam escapes. Modern autoclaves equipped automatic device that regulates the mode of operation. With an increase in steam pressure, the temperature in the autoclave also increases accordingly; so, at a pressure of 50.6 kPa, the temperature will be 110 ... I2X, At 101.3 kPa - 120 ... I21, at 151.9 kPa - 124 ... 126, at 202.6 kPa - 132 ... 133 X .
Pressure gauges register vapor pressure without regard to ambient atmospheric pressure(760 mm Hg). After the sterilization time has elapsed, the autoclave is turned off. After cooling, at zero reading of the pressure gauge, the ann is opened to let off steam. The lid of the autoclave is carefully pulled over without looking into the boiler, protecting the face from possible exposure to residual steam. It is impossible to open the lid of the autoclave until the steam has completely escaped, because with a rapid drop in pressure inside the autoclave, the sterilized liquid media boil, and the stoppers from the test tubes are pushed out along with the liquid.
Rice. 29. (Bottom) Scheme of a vertical and horizontal autoclave:
/(- vertical autoclave: /-stand; 2 - water meter tube; 3- voroyka; 4-safety valve; 5 - manometer; d - cover; 7 screw terminals; S- boiler; 9- casing;
10- sterilization chamber; // - water vapor chamber; /2 - steam outlet valve. I - horizontal autoclave: U - pedestal; 2 - a heating element; 3 - boiler cover; 4-safety valve; J-valve; 6- casing; 7-steam chamber; 8- sterilization chamber; 9 - steam chamber manometer; 10 - three-way valve; // - siphon tube of the steam chamber; 12 - support ring; 13 - steam chamber cover; 14- steering wheel; /5-inlet valve; /6-manometer of the pot; 17- three-way valve of the kettle; 18- siphon tube of the kettle; 19- pipe branch; 20- funnel; 21 - water column; 22- bowler hat
With an increase in steam pressure, the temperature in the autoclave also increases accordingly; so, at a pressure of 50.6 kPa, the temperature will be 110 ... I2X, At 101.3 kPa - 120 ... I21, at 151.9 kPa - 124 ... 126, at 202.6 kPa - 132 ... 133 X .
The manometers record the vapor pressure without taking into account the ambient atmospheric pressure (760 mmHg). After the sterilization time has elapsed, the autoclave is turned off. After cooling, at zero reading of the pressure gauge, open the valve to release the steam. The lid of the autoclave is carefully pulled over without looking into the boiler, protecting the face from possible exposure to residual steam. It is impossible to open the lid of the autoclave until the steam has completely escaped, because with a rapid drop in pressure inside the autoclave, the sterilized liquid media boil, and the stoppers from the test tubes are pushed out along with the liquid.
Nutrient media that can withstand heating above 100 ° C, glassware wrapped in paper, dressings, dressing gowns placed in metal biks are sterilized in an autoclave. In addition, used bacterial cultures and dishes are disinfected. In these cases, the steam pressure and sterilization exposure are longer (151.9 kPa-1 h) than with sterilization pure material(50.6..L01, ZkPa - 30...40 min).
Various substances (benzonaphthol, antipyrine, sulfur) with a certain melting point are used to check the quality of the autoclave, the correspondence of the pressure gauge readings and the steam temperature. A small amount of this substance is mixed with the same amount of dye (magenta, methylene blue), placed in a test tube, sealed and placed in a vertical position between the material to be sterilized. At the right temperature, the indicator substance melts and turns into the color of the dye used.
The device of horizontal autoclaves is structurally different from vertical ones, but the principle of operation remains the same.
Sterilization by filtration. It is carried out by passing the material through bacteriological filters. Filtering is not only about passing or delaying a filter smallest particles(bacteria) depending on the size of the pores of the filter plate, but also on the adsorption capacity of the material from which the filter is made. Usually they filter liquids that cannot withstand heating (serums, antibiotic solutions, etc.). When filtered
Rice. 30. Seitz Filter:
/ - glass flask Buneen; 2 - cannula for air suction; 3 - metal holder; 4 - filter
nye plates from a mixture of asbestos with cellulose. Domestic asbestos filters have grades F2 and SF. Sterilizing filters are brand SF.
Membrane(ultra-) filters(colloidal membranes) look like the thinnest sheets of white paper. They are prepared from hemicellulose treated with appropriate reagents, temperature and pressing. These filters are distinguished by the diameter and size of the pores. They are used for filtration, the concentration of particles contained in the filtered liquid, and also for determining the size of viruses.
The sterility of the obtained filtrates is checked by inoculation on nutrient media, followed by keeping in a thermostat for several days.
Sterilization by ultraviolet radiation (UVR). In the laboratory, special germicidal lamps usually serve as a source of UV radiation. UV irradiation is used for air disinfection in rooms (boxes, operating rooms). Germicidal lamps have also found application in trade and Food Industry when storing various products at temperatures above 0 °C.
Ultrasound. A certain frequency is used as a physical sterilizing factor, for example, for the disinfection of soda, sterilization of milk, some canned products, raw hides.
Chemical Methods. Not suitable for sterilization of nutrient media and laboratory glassware. They are more often used to preserve certain substrates, since they paralyze the enzymatic ability of bacteria in bactericidal concentrations.
In some cases, biological METHODS are used for sterilization.
At a temperature of 132 degrees - a pressure of 2 kgf / sq. cm for 20 minutes.
At a temperature of 120 degrees - a pressure of 1.1 kgf / sq. cm for 45 minutes.
Dressings and surgical linen are sterilized in steam sterilizers in biks or in bags of dense material (with strings such as a pouch). The serviceability of this device must be checked every time before laying the material in the bix, if the tightness is broken, then the contents of the bix become infected. Before laying the bix, a 2-fold hygienic treatment bix with external and inside slut. The material used for packaging, sheets or napkins used to cover the sterile table, are washed once a week. When sterilizing the material in bags, the material is packed in two bags, put one on top of the other. All materials are stacked vertically in such a way that you can immediately find what you need without removing anything superfluous from the bix. All materials are laid loosely so that steam can freely penetrate into the depth between the linen and inside the rolls. Each bix must be labeled with information about the contents, the date of sterilization, as well as the department to which the bix belongs. An indicator for sterility control is placed in each bix, since there must be complete confidence that the complete destruction of microbes (de-fertilization) has occurred.
Steam sterilization is controlled different methods. It is possible, for example, to register a high temperature and the duration of sterilization at this temperature. Heat-sensitive chemical indicators are also used, which are applied to outside each package. They do not indicate the sterility of the items inside the package, but indicate whether the package has been sterilized. When sterilizing large packages, the indicator is placed inside it. An external indicator shows whether steam has entered the package.
Bacteriological quality control steam sterilization carried out at least once a month, carried out by the sanitary service. Standard bacteriological indicators are used, containing a dosed amount of microbial spores, which are especially resistant to hot steam, and their death indicates the complete sterility of objects. If the autoclave is in good working order and the sterilization regimen is followed, the spores usually die. A single germination of spores does not necessarily indicate that the treated items are not sterile. In this case, it is necessary to check the sterilization mode (temperature and duration), correct loading of the autoclave and its operation, and then repeat the test.
When using this method of sterilization, the effect is combined high temperature and humidity. If dry heat causes mainly pyrogenetic destruction of microorganisms, then damp heat- protein coagulation, requiring the participation of water. In practice, sterilization wet steam is carried out at a temperature of 50-150 ° C and is carried out in the following ways.
Boiling. This method sterilizes rubber objects, surgical (non-disposable) instruments, glassware. It is not recommended to use boiling for sterilization of injection solutions, since in terms of efficiency it is significantly inferior to steam sterilization and often leads to a decrease in the therapeutic effect of the drug.
Steam sterilization. Fluid is called saturated water vapor (without admixture of air), having a pressure of 760 mm Hg. Art. and a temperature of 100 °C. Sterilization with flowing steam is carried out in a steam sterilizer or autoclave for 15-60 minutes, depending on the volume of the solution. This is the most common method for sterilizing injectable solutions in pharmacies.
Steam sterilization under pressure, or autoclaving. Implemented in various designs autoclaves. The autoclave is a hermetically sealed container, consisting of a thick-walled sterilization chamber and a casing.
The autoclave has a safety valve that allows steam to escape at excess pressure, and a pressure gauge. Each autoclave must have instructions for use and care. The object to be sterilized is placed inside the steam chamber. The steam chamber is heated. First, the autoclave is heated with the tap open until the steam go strong continuous jet and will not displace the air in the autoclave, which significantly reduces the thermal conductivity of water vapor (with a content of 5% air in water vapor, it decreases by 50%). During the heating of the autoclave after closing the valve, it is necessary to monitor the pressure, in parallel with the increase of which the temperature of the steam increases. The relationship between temperature and vapor pressure is expressed as follows: 1 atm - 100 °C; 1.5 atm - 112.7 ° C; 2 atm - 119.6 ° C; 3 atm - 132.9 ° С; 5 atm - 151.1 ° C. Autoclaving is the most reliable sterilization method. Typically, sterilization in an autoclave is carried out at 120 °C for 5-30 minutes, depending on the volume of the solution. This guarantees a sufficiently complete sterilization, regardless of the type of microorganism. In this way, dishes, filters, instruments, aqueous solutions of high-temperature-resistant medicinal substances, dressings are sterilized.
Fractional sterilization. In fractional sterilization, an object (usually an aqueous solution) is heated with fluid steam at 100°C for 30 minutes, then the solution is kept at room temperature for 24 hours, after which it is sterilized again under the same conditions (30 minutes at 100°C). The described cycle is repeated 3-5 times. During the first heating, vegetative forms of microoranisms die, during subsequent heating, newly appeared forms and spores.
Pasteurization. This is a single heating of the object at a temperature of 6 °C for 1 hour or at a temperature of 70-80 °C for 30 minutes. Pasteurization allows you to destroy the vegetative forms of microorganisms (except theophilic), but not spores.
Tindalization (fractional pasteurization). During tyndalization, the object is heated at a temperature of 60-65 °C for 1 hour daily for 5 days or at a temperature of 70-80 °C for 3 days. This is a reliable and gentle way to sterilize thermolabile medicinal substances. However, due to its duration, it is of little use for pharmacies and is currently almost never used. These are the main thermal processes used in pharmaceutical practice.