Uses | Sterilization |
---|---|
Inventor | Charles Chamberland |
Related items | Waste autoclave |
An autoclave is a machine used to carry out industrial and scientific processes requiring elevated temperature and pressure in relation to ambient pressure and/or temperature. Autoclaves are used before surgical procedures to perform sterilization and in the chemical industry to cure coatings and vulcanize rubber and for hydrothermal synthesis. Industrial autoclaves are used in industrial applications, especially in the manufacturing of composites.
Many autoclaves are used to sterilize equipment and supplies by subjecting them to pressurized saturated steam at 121 °C (250 °F) for 30–60 minutes at a gauge pressure of 103 kPa [1] (about double atmospheric pressure) depending on the size of the load and the contents. [2] The autoclave was invented by Charles Chamberland in 1879, [3] although a precursor known as the steam digester was created by Denis Papin in 1679. [4] The name comes from Greek auto-, ultimately meaning self, and Latin clavis meaning key, thus a self-locking device. [5]
Sterilization autoclaves are widely used in microbiology and mycology, medicine and prosthetics fabrication, tattooing and body piercing, and funerary practice. They vary in size and function depending on the media to be sterilized and are sometimes called retort in the chemical and food industries.
Typical loads include laboratory glassware, other equipment and waste, surgical instruments, and medical waste. [6] [7]
A notable recent and increasingly popular application of autoclaves is the pre-disposal treatment and sterilization of waste material, such as pathogenic hospital waste. Machines in this category largely operate under the same principles as conventional autoclaves in that they are able to neutralize (but not eliminate) potentially infectious agents by using pressurized steam and superheated water. [8]
Autoclaves are also widely used to cure composites, especially for melding multiple layers without any voids that would decrease material strength, and in the vulcanization of rubber. [9] The high heat and pressure that autoclaves generate help to ensure that the best possible physical properties are repeatable. Manufacturers of spars for sailboats have autoclaves well over 50 feet (15 m) long and 10 feet (3 m) wide, and some autoclaves in the aerospace industry are large enough to hold whole airplane fuselages made of layered composites. [10]
A thermal effluent decontamination system functions as a single-purpose autoclave designed for the sterilization of liquid waste and effluent.
It is very important to ensure that all of the trapped air is removed from the autoclave before activation, as trapped air is a very poor medium for achieving sterility. Steam at 134 °C (273 °F) can achieve a desired level of sterility in three minutes, while achieving the same level of sterility in hot air requires two hours at 160 °C (320 °F). [11] Methods of air removal include:
Stovetop autoclaves used in poorer or non-medical settings do not always have automatic air removal programs. The operator is required to manually perform steam pulsing at certain pressures as indicated by the gauge. [12]
A medical autoclave is a device that uses steam to sterilize equipment and other objects. This means that all bacteria, viruses, fungi, and spores are inactivated. [13] However, prions, such as those associated with Creutzfeldt–Jakob disease, and some toxins released by certain bacteria, such as Cereulide, may not be destroyed by autoclaving at the typical 134 °C for three minutes or 121 °C for 15 minutes and instead should be immersed in sodium hydroxide (1M NaOH) and heated in a gravity displacement autoclave at 121 °C for 30 min, cleaned, rinsed in water and subjected to routine sterilization. [14] Although a wide range of archaea species, including Geogemma barossii (Strain 121) , can survive and even reproduce at temperatures found in autoclaves, their growth rate is so slow at the lower temperatures in the less extreme environments occupied by humans that it is unlikely they could compete with other organisms. [15] None of them are known to be infectious or otherwise pose a health risk to humans; in fact, their biochemistry is so different from that of humans, and their multiplication rate is so slow, that microbiologists need not worry about them. [16]
Autoclaves are found in many medical settings, laboratories, and other places that need to ensure the sterility of an object. Many procedures today employ single-use items rather than sterilizable, reusable items. This first happened with hypodermic needles, but today many surgical instruments (such as forceps, needle holders, and scalpel handles) are commonly single-use rather than reusable items (see waste autoclave).
Because damp heat is used, heat-labile products (such as some plastics) cannot be sterilized this way or they will melt. Paper and other products that may be damaged by steam must also be sterilized another way. In all autoclaves, items should always be separated to allow the steam to penetrate the load evenly.
Autoclaving is often used to sterilize medical waste prior to disposal in the standard municipal solid waste stream. This application has become more common as an alternative to incineration due to environmental and health concerns about the combustion by-products emitted by incinerators, especially from the small units which were commonly operated at individual hospitals. Incineration or a similar thermal oxidation process is still generally mandated for pathological waste and other very toxic or infectious medical waste. For liquid waste, an effluent decontamination system is the equivalent hardware.
In dentistry, autoclaves provide sterilization of dental instruments.
In most of the industrialized world medical-grade autoclaves are regulated medical devices. Many medical-grade autoclaves are therefore limited to running regulator-approved cycles. Because they are optimized for continuous hospital use, they favor rectangular designs, require demanding maintenance regimens, and are costly to operate. (A properly calibrated medical-grade autoclave uses thousands of gallons of water each day, independent of task, with correspondingly high electric power consumption.)
Autoclaves are used in education, research, biomedical research, pharmaceutical research and industrial settings to sterilize lab instruments and glassware, process waste loads prior to disposal, prepare culture media and liquid media, and artificially age materials for testing.
Although autoclaves produced for use in medicine may be used in research settings, labs may opt for "research-grade" autoclaves. These are specifically designed for non-medical applications. Research autoclaves often use a “jacketless” design where steam is generated directly in the pressure chamber using heating coils (rather than relying on a “steam jacket” and independent steam generator, as is the case in high-throughput medical autoclaves). Research-grade autoclaves do not have to meet stringent requirements associated with sterilizing instruments that will be directly used on humans. Instead they can prioritize efficiency, programming flexibility, ease-of-use, and sustainability.
In 2016, the Office of Sustainability at the University of California, Riverside (UCR) conducted a study of autoclave efficiency in their genomics and entomology research labs, tracking several units' power and water consumption. They found that, even when functioning within intended parameters, the medical-grade autoclaves used in their research labs were each consuming 700 gallons of water and 90 kWh of electricity per day (1,134MWh of electricity and 8.8 million gallons of water total), because they consumed energy and water continuously, even when not in use. UCR's research-grade autoclaves performed the same tasks with equal effectiveness, but used 83% less energy and 97% less water. [17]
The University of Alabama at Birmingham (UAB) completed a similar study in 2023 in order to assess the performance differences between similar-sized jacketed and non-jacketed autoclaves performing identical tasks in a research setting. They monitored side-by-side autoclaves in a facility running cycles indicative of the most common load and sterilization tasks used by their researchers campuswide. UAB found that jacketed autoclaves consumed significantly more water (44–50 gallons per cycle) and house steam (25–41 pounds per cycle) than non-jacketed autoclaves, which used less than 2 gallons of water and no house steam per cycle, regardless of cycle type or task. The higher water use by jacketed autoclaves resulted in an estimated water cost of $764 per jacketed autoclave per year, compared to $23 for non-jacketed autoclaves. With over 100 steam-jacketed autoclaves on campus, the author calculated that using jacketed autoclaves for research tasks translated into an additional $74,000 in annual excess spending for UAB. In addition, jacketed autoclaves had a higher initial purchase price than non-jacketed equivalents (37% more). The author also noted anecdotal reports of electrical utility and maintenance cost savings associated with non-jacketed autoclaves. [18]
Research autoclaves display a wide range of designs and sizes, and are frequently tailored to their use and load type. Common variations include either a cylindrical or square pressure chamber, air- or water-cooling systems, and vertically or horizontally opening chamber doors (which may be electrically or manually powered). Research-grade autoclaves may be configured for "pass-through" operation. This makes it possible to maintain absolute isolation between "clean" and potentially contaminated work areas. Pass-through research autoclaves are especially important in BSL-3 or BSL-4 facilities.
In order to sterilize items effectively, it is important to use optimal parameters when running an autoclave cycle. A 2017 study performed by the Johns Hopkins Hospital biocontainment unit tested the ability of pass-through autoclaves to decontaminate loads of simulated biomedical waste when run on the factory default setting. The study found that 18 of 18 (100%) mock patient loads (6 PPE, 6 linen, and 6 liquid loads) passed sterilization tests with the optimized parameters compared to only 3 of 19 (16%) mock loads that passed with use of the factory default settings. [19]
There are physical, chemical, and biological indicators that can be used to ensure that an autoclave reaches the correct temperature for the correct amount of time. If a non-treated or improperly treated item can be confused for a treated item, then there is the risk that they will become mixed up, which, in some areas such as surgery, is critical.
Chemical indicators on medical packaging and autoclave tape change color once the correct conditions have been met, indicating that the object inside the package, or under the tape, has been appropriately processed. Autoclave tape is only a marker that steam and heat have activated the dye. The marker on the tape does not indicate complete sterility. A more difficult challenge device, named the Bowie-Dick device after its inventors, is also used to verify a full cycle. This contains a full sheet of chemical indicator placed in the center of a stack of paper. It is designed specifically to prove that the process achieved full temperature and time required for a normal minimum cycle of 134 °C for 3.5–4 minutes. [20]
To prove sterility, biological indicators are used. Biological indicators contain spores of a heat-resistant bacterium, Geobacillus stearothermophilus . If the autoclave does not reach the right temperature, the spores will germinate when incubated and their metabolism will change the color of a pH-sensitive chemical. Some physical indicators consist of an alloy designed to melt only after being subjected to a given temperature for the relevant holding time. If the alloy melts, the change will be visible. [21]
Some computer-controlled autoclaves use an F0 (F-nought) value to control the sterilization cycle. F0 values are set for the number of minutes of sterilization equivalent to 121 °C (250 °F) at 103 kPa (14.9 psi) above atmospheric pressure for 15 minutes. Since exact temperature control is difficult, the temperature is monitored, and the sterilization time adjusted accordingly. [22]
A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be transformed by a connecting rod and crank into rotational force for work. The term "steam engine" is most commonly applied to reciprocating engines as just described, although some authorities have also referred to the steam turbine and devices such as Hero's aeolipile as "steam engines". The essential feature of steam engines is that they are external combustion engines, where the working fluid is separated from the combustion products. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In general usage, the term steam engine can refer to either complete steam plants, such as railway steam locomotives and portable engines, or may refer to the piston or turbine machinery alone, as in the beam engine and stationary steam engine.
A boiler is a closed vessel in which fluid is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central heating, boiler-based power generation, cooking, and sanitation.
Sterilization refers to any process that removes, kills, or deactivates all forms of life and other biological agents present in fluid or on a specific surface or object. Sterilization can be achieved through various means, including heat, chemicals, irradiation, high pressure, and filtration. Sterilization is distinct from disinfection, sanitization, and pasteurization, in that those methods reduce rather than eliminate all forms of life and biological agents present. After sterilization, fluid or an object is referred to as being sterile or aseptic.
A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy. On land, when used to make electricity the most common type is called a combined cycle gas turbine (CCGT) plant, which is a kind of gas-fired power plant. The same principle is also used for marine propulsion, where it is called a combined gas and steam (COGAS) plant. Combining two or more thermodynamic cycles improves overall efficiency, which reduces fuel costs.
Cogeneration or combined heat and power (CHP) is the use of a heat engine or power station to generate electricity and useful heat at the same time.
A chiller is a machine that removes heat from a liquid coolant via a vapor-compression, adsorption refrigeration, or absorption refrigeration cycles. This liquid can then be circulated through a heat exchanger to cool equipment, or another process stream. As a necessary by-product, refrigeration creates waste heat that must be exhausted to ambience, or for greater efficiency, recovered for heating purposes. Vapor compression chillers may use any of a number of different types of compressors. Most common today are the hermetic scroll, semi-hermetic screw, or centrifugal compressors. The condensing side of the chiller can be either air or water cooled. Even when liquid cooled, the chiller is often cooled by an induced or forced draft cooling tower. Absorption and adsorption chillers require a heat source to function.
Supercritical carbon dioxide is a fluid state of carbon dioxide where it is held at or above its critical temperature and critical pressure.
Infection prevention and control is the discipline concerned with preventing healthcare-associated infections; a practical rather than academic sub-discipline of epidemiology. In Northern Europe, infection prevention and control is expanded from healthcare into a component in public health, known as "infection protection". It is an essential part of the infrastructure of health care. Infection control and hospital epidemiology are akin to public health practice, practiced within the confines of a particular health-care delivery system rather than directed at society as a whole.
A waste autoclave is a form of solid waste treatment that uses heat, steam and pressure of an industrial autoclave in the processing of waste. Waste autoclaves process waste either in batches or in continuous-flow processes. In batch processes, saturated steam is pumped into the autoclave at temperatures around 160 °C, or 320 °F. The steam pressure in the vessel is maintained up to 6 bars (gauge) for a period of up to 45 minutes to allow the process to fully 'cook' the waste. The autoclave process gives a very high pathogen and virus kill rate, although the fibrous products which come from the process are susceptible to bacteria and fungus as they are high in starch, cellulose and amino acids. When designed for sterilizing waste containing mostly liquids, a waste autoclave is known as an Effluent Decontamination System.
Hot air ovens are electrical devices which use dry heat to sterilize. They were originally developed by Louis Pasteur, and are essentially the same as fan ovens used for cooking food. Generally, they use a thermostat to control the temperature. Their double walled insulation keeps the heat in and conserves energy, the inner layer being a poor conductor and outer layer being metallic. There is also an air filled space in between to aid insulation. An air circulating fan helps in uniform distribution of the heat. These are fitted with the adjustable wire mesh plated trays or aluminium trays and may have an on/off rocker switch, as well as indicators and controls for temperature and holding time. The capacities of these ovens vary. Power supply needs vary from country to country, depending on the voltage and frequency (hertz) used. Temperature sensitive tapes or biological indicators using bacterial spores can be used as controls, to test for the efficacy of the device during use.
Dry heat sterilization of an object is one of the earliest forms of sterilization practiced. It uses hot air that is either free from water vapor or has very little of it, where this moisture plays a minimal or no role in the process of sterilization.
Moist heat sterilization describes sterilization techniques that use hot water vapor as a sterilizing agent. Heating an article is one of the earliest forms of sterilization practiced. The various procedures used to perform moist heat sterilization process cause destruction of micro-organisms by denaturation of macromolecules.
Biomedical waste or hospital waste is any kind of waste containing infectious materials generated during the treatment of humans or animals as well as during research involving biologics. It may also include waste associated with the generation of biomedical waste that visually appears to be of medical or laboratory origin, as well research laboratory waste containing biomolecules or organisms that are mainly restricted from environmental release. As detailed below, discarded sharps are considered biomedical waste whether they are contaminated or not, due to the possibility of being contaminated with blood and their propensity to cause injury when not properly contained and disposed. Biomedical waste is a type of biowaste.
Vaporized hydrogen peroxide (trademarked VHP, also known as hydrogen peroxide vapor, HPV) is a vapor form of hydrogen peroxide (H2O2) with applications as a low-temperature antimicrobial vapor used to decontaminate enclosed and sealed areas such as laboratory workstations, isolation and pass-through rooms, and even aircraft interiors.
Steam is water vapour, often mixed with air and/or an aerosol of liquid water droplets. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization. Steam that is saturated or superheated is invisible; however, wet steam, a visible mist or aerosol of water droplets, is often referred to as "steam".
A waste converter is a machine used for the treatment and recycling of solid and liquid refuse material. A converter is a self-contained system capable of performing the following functions: pasteurization of organic waste; sterilization of pathogenic or biohazard waste; grinding and pulverization of refuse into unrecognizable output; trash compaction; dehydration. Because of the wide variety of functions available on converters, this technology has found application in diverse waste-producing industrial segments. Hospitals, clinics, municipal waste facilities, farms, slaughterhouses, supermarkets, ports, sea vessels, and airports are the primary beneficiaries of on-site waste conversion.
Package testing or packaging testing involves the measurement of a characteristic or property involved with packaging. This includes packaging materials, packaging components, primary packages, shipping containers, and unit loads, as well as the associated processes.
The central sterile services department (CSSD), also called sterile processing department (SPD), sterile processing, central supply department (CSD), or central supply, is an integrated place in hospitals and other health care facilities that performs sterilization and other actions on medical devices, equipment and consumables; for subsequent use by health workers in the operating theatre of the hospital and also for other aseptic procedures, e.g. catheterization, wound stitching and bandaging in a medical, surgical, maternity or paediatric ward.
A distilling ship is a class of military ships, generally converted tankers, with the capability to convert salt water into fresh water. They were typically stationed at forward bases during conflict where they supported on-the-ground troops and front line naval units.
An effluent decontamination system (EDS) is a device, or suite of devices, designed to decontaminate or sterilise biologically active or biohazardous materials in fluid and liquid waste material. Facility types that may utilise an EDS include hospitals, food and beverage industry plants, research laboratories, agricultural and animal research facilities, pharmaceutical production facilities, and governmental or military facilities. In fact, all facilities in the United States of America that produce liquid waste of Biosafety Level 2 and above must decontaminate their waste before discharging it into a public sewer system. Examples of liquids sterilised in an EDS include the shower water from personnel decontamination rooms, and the waste water from washing down animal rooms in laboratory environments.
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: CS1 maint: numeric names: authors list (link)Immerse in sodium hydroxide (NaOH)20 and heat in a gravity displacement autoclave at 121°C for 30 min; clean; rinse in water and subject to routine sterilization.