On This Page On This Page Purchase with Confidence Make an informed autoclave purchasing decision by asking these key questions before you buy. Download the eBook The Different Types of Autoclaves [& How to Choose the Right One] Written by: Arthur Trapotsis MS Biochemical Engineering, MBA, Consultant Steam sterilizers — also known as autoclaves — are an essential piece of equipment in any laboratory, research, or healthcare setting, ensuring sterility for important equipment and instruments. Autoclaves are available in a wide array of designs, each tailored for specific applications, ranging from small-scale laboratory sterilization to large-volume industrial processes. Autoclaves are categorized by three variables: Class, which determines air removal method and load compatibility Function, which determines physical configuration and workflow fit Capacity, which determines how much you can sterilize per cycle The right autoclave for your facility will depend on what you’re sterilizing, how often, and what your space and utilities can support. If you’re replacing an existing unit or speccing one into a new facility, the single most important question to answer first is what type of load you need to sterilize. Everything else follows from there. In this article, we’ll explore the various types of autoclaves, including their distinct applications, advantages, and critical considerations when selecting the appropriate model based on your unique operational requirements. Key Takeaways Autoclaves are categorized by class, function, and capacity. Class B autoclaves use vacuum-assisted air removal and can handle the widest range of load types, including porous and hollow items. Pass-through autoclaves are required for biosafety levels 3 and 4 (BSL-3 and BSL-4) biocontainment facilities and are also found in cleanrooms and pharmaceutical manufacturing, where sterile zone integrity is critical. Autoclave performance is verified through a combination of mechanical, chemical, and biological indicators. Choosing the wrong autoclave for your load type is one of the most common and costly mistakes in facility planning. Steam Sterilization: A Brief Overview Steam sterilization, also known as moist heat sterilization, is the most effective and widely used method for sterilizing equipment in a variety of industries. Steam sterilization uses pressurized steam to eliminate harmful microorganisms, including bacteria, viruses, fungi, and spores, from surfaces and instruments. This saturated steam under pressure increases the temperature within an autoclave chamber to levels that effectively denature proteins and enzymes in microbial cells, rendering them non-viable. A typical steam sterilization cycle involves several stages designed to ensure thorough decontamination. The process begins with an initial purge, during which air is evacuated from the autoclave chamber, and then a conditioning phase, during which that air is replaced by steam. These phases are crucial, as the presence of air pockets within the chamber can impede the efficient transfer of heat. Once the chamber is saturated with steam, the temperature and pressure are elevated to predetermined levels, depending on the goods being sterilized. The standard temperature for most steam sterilization processes is 250°F (121°C), though certain applications may require higher temperatures, up to 270°F (132°C). Recognized minimum exposure times for sterilizing wrapped healthcare supplies are 30 minutes at 250°F in a gravity displacement sterilizer or 4 minutes at 270°F in a prevacuum sterilizer. After this phase, the steam is vented and allowed to depressurize. This is followed by a drying phase to remove excess moisture from the sterilization, which sometimes involves the application of a vacuum to expedite drying. The combination of heat, pressure, and moisture disrupts microbial structures, guaranteeing complete sterilization. The science behind steam sterilization is rooted in thermodynamics and microbiology. The high potential energy of steam condensing into water allows for more rapid heat transfer compared to dry heat, while the moisture content plays a vital role in denaturing proteins. In contrast to dry heat, which can take longer to penetrate surfaces, moist heat from steam transfers energy more efficiently. This sterilization is highly effective for a broad range of materials, provided they can withstand the temperature and pressure conditions within the autoclave. How Are Autoclaves Categorized? Autoclaves are typically categorized by their class, function, and capacity, each of which is based on the sterilizer’s performance and intended usage. Category 1: Class Autoclaves are typically divided into three classes: Class B, Class N, and Class S, each distinguished by their air removal method and the types of loads they can sterilize. Class B: These autoclaves use a vacuum pump to remove air from the chamber before the sterilization process begins. This pre-vacuum stage ensures that steam penetrates porous and hollow items effectively, making Class B autoclaves suitable for a wide range of materials, including textiles, wrapped instruments, and hollow instruments. Their versatility makes them ideal for demanding applications, such as in dental practices and hospitals where instruments with complex structures require thorough sterilization.It’s important to note that many goods, including liquids, should never be exposed to a vacuum because the negative pressure it generates can cause the liquids to boil violently. This can potentially damage the autoclave and risks injury to operators.Class B autoclaves for smaller clinical and laboratory applications are governed by EN 13060, the international standard for small steam sterilizers, which defines the performance requirements these units must meet to classify as Class B. Class N: Compared to Class B autoclaves, Class N autoclaves use gravity displacement to remove air, which is pushed out of the chamber by steam as it enters. Class N autoclaves are suitable for simple, solid unwrapped loads, such as stainless steel instruments and glassware. They are not recommended for porous loads, hollow instruments, or wrapped items, as gravity displacement does not guarantee complete air removal. Class S: Class S autoclaves are something of a hybrid between Class B and Class N autoclaves. Their specifications are determined by the manufacturer, and they often incorporate features from both classes, offering more flexibility in terms of what they can sterilize. However, their exact capabilities vary widely; two Class S autoclaves from different manufacturers may have meaningfully different capabilities. It’s important to consult product details and verify against your actual load requirements before purchasing a Class S model. Category 2: Function Autoclaves can also be categorized based on their design and functional characteristics, each of which influence their suitability for different types of loads and environments. Vertical Autoclaves: These autoclaves are characterized by their vertically oriented chambers, which open at the top. Vertical autoclaves tend to be smaller in size, making them ideal for facilities with limited space or for processing smaller loads. Their compact design is well-suited for research facilities, dental practices, doctor’s offices, and veterinary clinics. Horizontal Autoclaves: Featuring a horizontally oriented chamber, these autoclaves are designed for high-capacity sterilization and commonly used in hospitals and research institutions. Their larger chambers allow for greater load capacity, making them ideal for bulkier equipment or larger batches of instruments. Loading equipment options such as extendable shelving and rolling carts and carriages provide easier loading and unloading for operators, especially when dealing with heavier items or more frequent use. Pass-through Autoclaves: Designed for environments that require strict control over sterilization zones, pass-thru autoclaves are built with doors on either side of the chamber. This allows items to be sterilized in one room and removed in the other, preventing cross-contamination between sterile and non-sterile areas. Pass-thru autoclaves are commonly used in hospitals, pharmaceutical manufacturing, and biocontainment facilities, where maintaining separate zones is critical. Hinged Autoclaves: Hinged autoclaves feature a single door with a radial-arm hinge that allows for easy opening and closing. This design is well-suited for applications that require frequent access to the autoclave chamber. Hinged autoclaves are robust, durable, and often come with customizable chamber sizes, making them an excellent option for small and mid-sized facilities. Their simple, yet effective design allows for reliable performance while occupying a relatively compact footprint. Front-Loading Autoclaves: Front-loading autoclaves feature a horizontally oriented chamber designed for convenient, efficient sterilization of various materials. The front-facing door allows for easy loading and unloading of trays, racks, or other items, making it a popular choice across industries. To learn more about the CSS line of front-loading autoclaves, visit the product page. Tower Autoclaves: These autoclaves are designed with two vertically stacked chambers — hence the name “tower” — enabling facilities to increase their sterilization throughput without requiring additional floor space. Dual chamber tower autoclaves are especially valuable in environments with limited space but high-volume sterilization needs, such as sterile processing departments in healthcare facilities and high-throughput laboratories. By allowing simultaneous sterilization in both chambers or staggered cycles, tower autoclaves maximize efficiency and reduce downtime between loads. Category 3: Capacity The third and final way to categorize autoclaves is by their capacity. The size of an autoclave chamber determines the volume of goods it sterilizes in a single cycle and is an important factor when choosing the appropriate unit for your facility. Small Capacity Autoclaves: Small capacity autoclaves, also known as benchtop or tabletop autoclaves, are compact and portable. With chamber volumes ranging from 1 to 45 liters, these units are suitable for sterilizing smaller instruments, glassware, and media. Due to their small footprint, they’re easy to integrate into tight spaces or to mount on countertops, making them a cost-effective and efficient solution for low-volume sterilization needs. Small autoclaves are commonly used in facilities where space and budget are limited, but reliable sterilization is necessary. Medium Capacity Autoclaves: Medium capacity autoclaves typically offer chamber capacities between 45 and 200 liters, providing greater flexibility for a wider range of applications. These autoclaves are often used in veterinary clinics, ASCs, and mid-sized research facilities, all of which require moderate throughput. Their larger capacity (relative to small autoclaves) allows for the sterilization of multiple instrument trays, wrapped materials, and even larger glassware or equipment in a single cycle, increasing efficiency and reducing downtime.They’re a versatile option, striking a balance between capacity and design, making them suitable for facilities with moderate sterilization demands without requiring the space or investment needed for large capacity autoclaves. Large Capacity Autoclaves: Large autoclaves, or industrial autoclaves, have capacities exceeding 200 liters and are built for high-volume, large-scale sterilization. These units are essential for hospitals, pharmaceutical manufacturers, and industrial facilities where large quantities of materials or oversized equipment need to be processed regularly. Large capacity autoclaves can accommodate large trays, bedpans, or bio waste containers, making them indispensable in high-demand environments.Large capacity autoclaves typically require a pit to be dug into the floor of the facility, enabling the autoclave chamber to sit at floor level, with drain plumbing located underground. This allows operators to wheel goods on carts or racks directly into the autoclave chamber. How to Choose the Right Type of Autoclave for Your Facility There are several things to consider when selecting the appropriate class, function, and size of steam sterilizer for your facility. Here are some best practices to help you start your search: Determine what types of loads you need to run. The materials you plan to sterilize will largely dictate what type of autoclave you need. For example, complex loads such as wrapped instruments, porous materials, and red bagged waste products will likely require a Class B sterilizer with vacuum functionality. Simpler loads such as solid metal instruments, empty glassware, and liquids can often be handled by Class N autoclaves.Additionally, facilities working with liquids, biohazardous materials, or waste will benefit from autoclaves with specific cycle options suited to these load types. Understanding your load requirements is crucial to ensure you select a model that can accommodate the diversity and complexity of your sterilization needs. Consider the layout of your space. Every autoclave requires dedicated floorspace; understanding how to manage that space is essential for optimizing your facility’s layout and performance. When determining what size autoclave you need, consider whether your plumber will connect from the back or side, as this impacts how much space you’ll need for maintenance access and could increase your autoclave’s overall footprint.You’ll also need to think about door placement: Do you have sufficient space to accommodate a door that swings outward, or do you need one that slides vertically? Ensure that there’s enough clearance so it doesn’t disrupt your workflow and decide on the door hinge’s placement based on your facility’s layout. Check your utility requirements. Autoclaves have specific utility demands, including water supply, electrical power, and steam. If your facility does not have an existing steam source — also known as “house” steam — you might consider an autoclave with a built-in steam generator. Be sure to verify that your facility can meet your new autoclave’s electrical requirements and that you can easily integrate water supply and drainage into the workflow. It’s also important to consult your facilities management team to ensure the property utility connections are in place before installation to avoid downtime or costly modifications. Evaluate your capacity and throughput needs. Start by assessing how many cycles you need to run daily and the anticipated size of each load. While small benchtop autoclaves may be sufficient for low-volume facilities, larger facilities will likely require medium or large capacity autoclaves to meet higher sterilization demands. Consider factors such as cycle time and load density, making sure to choose a unit that can handle peak loads without creating operational bottlenecks to avoid interruptions to your regular workflow. Plan for maintenance and service. Routine maintenance is key to keeping your autoclave running at peak performance levels and preventing unexpected downtime. When choosing a model, consider the availability of service plans and whether the sterilizer uses proprietary or easily sourced parts. Look for units from a manufacturer that offers strong support services and preventative maintenance options to ensure longevity. Think about customization and future growth. As your facility’s needs evolve, so may your sterilization requirements. Some autoclave models offer customizable features, such as programmable cycles, additional shelving, or specialized loading carts. A flexible autoclave that you can adapt for future use is a smart investment, so consider whether the model you choose can accommodate potential growth or more advanced sterilization requirements further down the road. For even more advice on how to choose the right type of autoclave for your facility, download our free buyer’s guide. How Do You Know Your Autoclave Is Actually Working? Completing a sterilization cycle isn’t the same as confirming that sterilization was successful. It’s important that your autoclave performs as validated, which requires a systematic approach to monitoring. According to guidance from the Centers for Disease Control and Prevention (CDC), effective autoclave monitoring relies on three types of indicators used in combination: Mechanical indicators are built into the autoclave itself and record the time, temperature, and pressure profile of each cycle via a printout or digital log. They confirm that the autoclave reached the correct parameters during the cycle but cannot confirm that those conditions were achieved uniformly throughout the load. Chemical indicators — typically autoclave tape, cards, or papers — change color when exposed to steam at or above the target temperature. They provide a quick visual confirmation that the load was exposed to heat but, like mechanical indicators, do not confirm that the temperature was maintained for a sufficient duration throughout the load. Biological indicators (BIs) are the most definitive verification method. They contain a standardized population of heat-resistant bacterial spores — which is why they’re also known as spore tests — specifically used to measure sterilizer efficacy. If the autoclave successfully kills all spores in the BI during a cycle, it confirms that the unit reached the required temperature and sustained that temperature long enough to achieve sterilization. BIs are incubated after the cycle, and any observed spore growth indicates a sterilization failure.The CDC recommends daily BI testing for autoclaves that run multiple loads per day. A failed BI test should prompt immediate investigation. Verify that the autoclave was used correctly, check time and temperature settings, inspect the steam supply, and contact the manufacturer if the issue cannot be resolved. Items processed since the last successful BI test should be quarantined and reprocessed. Full cycle validation — including installation qualification, operational qualification, and performance qualification — is required for BSL-3, BSL-4, and regulated pharmaceutical facilities. This process documents that the autoclaved was installed correctly, performs to specification, and continues to achieve validated sterilization outcomes over time. Explore Consolidated’s Full Line of Autoclaves Since 1946, Consolidated Sterilizer Systems have manufactured state-of-the-art steam sterilizers for laboratories, research institutions, healthcare facilities, and more. Explore our full line of autoclaves today: Single Door Hinged Autoclave Our single door hinged autoclave features a radial-arm hinged door designed for ease of use. It is available in 11 different chamber sizes ranging from 16” x 16” x 26” and 3.9 cu. ft to 24″ x 36″ x 72″ and 26 cu. ft and offers both gravity and pre-vacuum cycles. Suitable for small and mid-sized facilities, its stainless-steel construction and customizable control options deliver optimal sterilization for a wide range of applications. See Details Here > Single Door Vertical Sliding Autoclave Featuring a space-saving vertical sliding door, this autoclave is perfect for labs with limited space. Available in chamber sizes up to 26” x 26” x 49” and 19.2 cu. ft, it supports pre-vacuum and gravity cycles, ensuring flexibility for a wide variety of sterilizations needs. Delivering high-performance steam sterilization and ergonomic efficiency, including easy access and minimized operational footprint, this autoclave is ideal for mid-sized and large facilities alike. See Details Here > Double Door Pass-thru Autoclave Designed for cleanroom and biocontainment facilities, our pass-thru autoclave features dual doors for sterile transfers between separate zones. With chamber sizes of up to 24″ x 36″ x 72″ and 36 cu. ft, it’s capable of supporting large loads and efficient workflow management in highly regulated environments. See Details Here > Dual Chamber Tower Autoclave This space-saving autoclave stacks two chambers vertically to offer a 35% smaller footprint than traditional side-by-side models. Ideal for high-volume operations, it features independent chambers, allowing for simultaneous or staggered sterilization cycles. Available in chamber sizes of up to 20″ x 20″ x 38″ and 8.8 cu. ft, this unit supports efficient large-scale sterilization in limited spaces. See Details Here > To learn more about any of our units, contact our team today or request a custom quote. Frequently Asked Questions Q: What are the four methods of sterilization? A: The four methods of sterilization most commonly found in laboratory and healthcare settings are: Steam sterilization (autoclaving): The most widely used method because it is fast, effective against the full spectrum of microorganisms, and relatively inexpensive Dry heat sterilization: Uses hot air at high temperatures for longer exposure times and is appropriate for materials that cannot tolerate moisture Chemical sterilization: Uses agents such as ethylene oxide or hydrogen peroxide vapor and is intended for heat-sensitive instruments and devices Radiation sterilization: Uses gamma rays, electron beams, or ultraviolet light; primarily used in industrial and pharmaceutical manufacturing for single-use devices and packaging Q: What is a steam sterilizer, and how does it work? A: A steam sterilizer, or autoclave, uses high-pressure saturated steam to sterilize loads. At a high-level, the autoclave heats water to produce steam, which then penetrates the load and transfers heat energy. As the temperature rises, the heat denatures proteins in microbial cells, effectively killing bacteria, viruses, fungi, and spores. Steam sterilization is the more efficient and effective sterilization method, making it popular for laboratory, research, healthcare, and industrial applications. Q: What types of materials can be autoclaved? A: Autoclaves are highly versatile pieces of equipment that can be used to sterilize a wide variety of materials, including (but not limited to): Metal instruments Glassware and lab equipment Textile Red bag waste Biohazardous materials Autoclave-safe plastics Solid and liquid media Animal cage bedding Soil samples Q: Are there any materials that should not be autoclaved? A: Yes, certain materials should not be autoclaved due to their sensitivity to high heat, pressure, and moisture. These include: Heat-sensitive plastics Flammable or volatile chemicals Powders (which can be compromised by moisture) Electronics Some metals (which can corrode) Certain chemical agents such as chloride, which can damage the autoclave or produce hazardous gases Always consult the manufacturer’s recommended instructions for use to determine the autoclave compatibility of specific materials. Q: What are the different types of autoclaves available? A: Autoclaves are categorized by: Class, including Class B, Class N, and Class S Function, including vertical autoclaves, horizontal autoclaves, pass-thru autoclaves, hinged autoclaves, and tower autoclaves Capacity, including small capacity autoclaves, medium capacity autoclaves, and large capacity autoclaves Q: What are the different types of autoclaves available? A: The different types of autoclaves available are categorized by three variables: Class, which determines air removal method and load compatibility; these include Class B, Class N, and Class S Function, which determines physical configuration and workflow fit; these include vertical autoclaves, horizontal autoclaves, pass-through autoclaves, hinged autoclaves, and tower autoclaves Capacity, which determines how much you can sterilize per cycle; these include small capacity autoclaves, medium capacity autoclaves, and large capacity autoclaves Q: What are the three types of autoclaves? A: The three types of autoclaves, as classified by their air removal method, are: Class B autoclaves, which use a vacuum pump for complete air removal and can handle the full range of load types, including porous, hollow, and wrapped instruments Class N autoclaves, which use gravity displacement and are suitable for simple, solid, unwrapped loads Class S autoclaves, which manufacturer-defined specifications that often incorporate elements of both Class B and Class N autoclaves, making their exact capabilities variable Q: How do I determine which type of autoclave is best for my facility? A: To determine which type of autoclave is best for your facility, consider: Load types: Are you sterilizing solid instruments, porous materials, or liquids? Certain loads may require gravity or pre-vacuum cycles. Capacity: What is your anticipated daily throughput? Smaller models may suffice for low volumes, while large capacity autoclaves are a requirement for high-demand environments. Space constraints: How much available floor space do you have? Be sure to account for plumbing configuration and door clearance when determining what size autoclave you can accommodate. Utility availability: Consider water, steam, and electrical requirements, making sure to consult your facilities management team, before selecting an autoclave. Q: What is the difference between a Class N and a Class B autoclave? A: The primary difference between Class B and Class N autoclaves is how they remove air from the chamber prior to sterilization. Class B autoclaves utilize a vacuum pump to completely remove air from the chamber, which enables steam to better penetrate the load. Class N autoclaves use steam from a boiler or generator to create downward displacement, which pushes air out of the chamber. Unlike a Class B autoclave, a Class N autoclave does not guarantee 100% air removal. For this reason, Class B autoclaves are preferable for more difficult loads that contain porous or hollow materials. Class N autoclaves are suitable for most standard applications. Q: What is the difference between a gravity displacement and a pre-vacuum steam sterilizer? A: A gravity sterilizer is any sterilizer that uses the gravity displacement method for air removal. Gravity sterilizers perform what’s known as a gravity cycle to sterilize loads. A pre-vacuum sterilizer is any sterilizer equipped with a vacuum system — either a water ejector or a liquid ring vacuum pump — to ensure air removal from the autoclave chamber. Pre-vacuum sterilizers are used to perform what are known as vacuum (or pre-vacuum) sterilization cycles; pre-vacuum sterilizers can also run gravity cycles. Q: What is a steam flush pressure pulse autoclave? A: A steam flush pressure pulse (SFPP) autoclave uses alternating steam flushes and pressure pulses (rather than a mechanical vacuum pump) to remove air from the chamber. 17 Questions to Ask Before Buying Your Next Autoclave We created this 17-question eBook as a framework to help you explore and discover the exact type of autoclave best suited to your needs. Get eBook Tweet Like Share
The Different Types of Autoclaves [& How to Choose the Right One] Written by: Arthur Trapotsis MS Biochemical Engineering, MBA, Consultant Steam sterilizers — also known as autoclaves — are an essential piece of equipment in any laboratory, research, or healthcare setting, ensuring sterility for important equipment and instruments. Autoclaves are available in a wide array of designs, each tailored for specific applications, ranging from small-scale laboratory sterilization to large-volume industrial processes. Autoclaves are categorized by three variables: Class, which determines air removal method and load compatibility Function, which determines physical configuration and workflow fit Capacity, which determines how much you can sterilize per cycle The right autoclave for your facility will depend on what you’re sterilizing, how often, and what your space and utilities can support. If you’re replacing an existing unit or speccing one into a new facility, the single most important question to answer first is what type of load you need to sterilize. Everything else follows from there. In this article, we’ll explore the various types of autoclaves, including their distinct applications, advantages, and critical considerations when selecting the appropriate model based on your unique operational requirements. Key Takeaways Autoclaves are categorized by class, function, and capacity. Class B autoclaves use vacuum-assisted air removal and can handle the widest range of load types, including porous and hollow items. Pass-through autoclaves are required for biosafety levels 3 and 4 (BSL-3 and BSL-4) biocontainment facilities and are also found in cleanrooms and pharmaceutical manufacturing, where sterile zone integrity is critical. Autoclave performance is verified through a combination of mechanical, chemical, and biological indicators. Choosing the wrong autoclave for your load type is one of the most common and costly mistakes in facility planning. Steam Sterilization: A Brief Overview Steam sterilization, also known as moist heat sterilization, is the most effective and widely used method for sterilizing equipment in a variety of industries. Steam sterilization uses pressurized steam to eliminate harmful microorganisms, including bacteria, viruses, fungi, and spores, from surfaces and instruments. This saturated steam under pressure increases the temperature within an autoclave chamber to levels that effectively denature proteins and enzymes in microbial cells, rendering them non-viable. A typical steam sterilization cycle involves several stages designed to ensure thorough decontamination. The process begins with an initial purge, during which air is evacuated from the autoclave chamber, and then a conditioning phase, during which that air is replaced by steam. These phases are crucial, as the presence of air pockets within the chamber can impede the efficient transfer of heat. Once the chamber is saturated with steam, the temperature and pressure are elevated to predetermined levels, depending on the goods being sterilized. The standard temperature for most steam sterilization processes is 250°F (121°C), though certain applications may require higher temperatures, up to 270°F (132°C). Recognized minimum exposure times for sterilizing wrapped healthcare supplies are 30 minutes at 250°F in a gravity displacement sterilizer or 4 minutes at 270°F in a prevacuum sterilizer. After this phase, the steam is vented and allowed to depressurize. This is followed by a drying phase to remove excess moisture from the sterilization, which sometimes involves the application of a vacuum to expedite drying. The combination of heat, pressure, and moisture disrupts microbial structures, guaranteeing complete sterilization. The science behind steam sterilization is rooted in thermodynamics and microbiology. The high potential energy of steam condensing into water allows for more rapid heat transfer compared to dry heat, while the moisture content plays a vital role in denaturing proteins. In contrast to dry heat, which can take longer to penetrate surfaces, moist heat from steam transfers energy more efficiently. This sterilization is highly effective for a broad range of materials, provided they can withstand the temperature and pressure conditions within the autoclave. How Are Autoclaves Categorized? Autoclaves are typically categorized by their class, function, and capacity, each of which is based on the sterilizer’s performance and intended usage. Category 1: Class Autoclaves are typically divided into three classes: Class B, Class N, and Class S, each distinguished by their air removal method and the types of loads they can sterilize. Class B: These autoclaves use a vacuum pump to remove air from the chamber before the sterilization process begins. This pre-vacuum stage ensures that steam penetrates porous and hollow items effectively, making Class B autoclaves suitable for a wide range of materials, including textiles, wrapped instruments, and hollow instruments. Their versatility makes them ideal for demanding applications, such as in dental practices and hospitals where instruments with complex structures require thorough sterilization.It’s important to note that many goods, including liquids, should never be exposed to a vacuum because the negative pressure it generates can cause the liquids to boil violently. This can potentially damage the autoclave and risks injury to operators.Class B autoclaves for smaller clinical and laboratory applications are governed by EN 13060, the international standard for small steam sterilizers, which defines the performance requirements these units must meet to classify as Class B. Class N: Compared to Class B autoclaves, Class N autoclaves use gravity displacement to remove air, which is pushed out of the chamber by steam as it enters. Class N autoclaves are suitable for simple, solid unwrapped loads, such as stainless steel instruments and glassware. They are not recommended for porous loads, hollow instruments, or wrapped items, as gravity displacement does not guarantee complete air removal. Class S: Class S autoclaves are something of a hybrid between Class B and Class N autoclaves. Their specifications are determined by the manufacturer, and they often incorporate features from both classes, offering more flexibility in terms of what they can sterilize. However, their exact capabilities vary widely; two Class S autoclaves from different manufacturers may have meaningfully different capabilities. It’s important to consult product details and verify against your actual load requirements before purchasing a Class S model. Category 2: Function Autoclaves can also be categorized based on their design and functional characteristics, each of which influence their suitability for different types of loads and environments. Vertical Autoclaves: These autoclaves are characterized by their vertically oriented chambers, which open at the top. Vertical autoclaves tend to be smaller in size, making them ideal for facilities with limited space or for processing smaller loads. Their compact design is well-suited for research facilities, dental practices, doctor’s offices, and veterinary clinics. Horizontal Autoclaves: Featuring a horizontally oriented chamber, these autoclaves are designed for high-capacity sterilization and commonly used in hospitals and research institutions. Their larger chambers allow for greater load capacity, making them ideal for bulkier equipment or larger batches of instruments. Loading equipment options such as extendable shelving and rolling carts and carriages provide easier loading and unloading for operators, especially when dealing with heavier items or more frequent use. Pass-through Autoclaves: Designed for environments that require strict control over sterilization zones, pass-thru autoclaves are built with doors on either side of the chamber. This allows items to be sterilized in one room and removed in the other, preventing cross-contamination between sterile and non-sterile areas. Pass-thru autoclaves are commonly used in hospitals, pharmaceutical manufacturing, and biocontainment facilities, where maintaining separate zones is critical. Hinged Autoclaves: Hinged autoclaves feature a single door with a radial-arm hinge that allows for easy opening and closing. This design is well-suited for applications that require frequent access to the autoclave chamber. Hinged autoclaves are robust, durable, and often come with customizable chamber sizes, making them an excellent option for small and mid-sized facilities. Their simple, yet effective design allows for reliable performance while occupying a relatively compact footprint. Front-Loading Autoclaves: Front-loading autoclaves feature a horizontally oriented chamber designed for convenient, efficient sterilization of various materials. The front-facing door allows for easy loading and unloading of trays, racks, or other items, making it a popular choice across industries. To learn more about the CSS line of front-loading autoclaves, visit the product page. Tower Autoclaves: These autoclaves are designed with two vertically stacked chambers — hence the name “tower” — enabling facilities to increase their sterilization throughput without requiring additional floor space. Dual chamber tower autoclaves are especially valuable in environments with limited space but high-volume sterilization needs, such as sterile processing departments in healthcare facilities and high-throughput laboratories. By allowing simultaneous sterilization in both chambers or staggered cycles, tower autoclaves maximize efficiency and reduce downtime between loads. Category 3: Capacity The third and final way to categorize autoclaves is by their capacity. The size of an autoclave chamber determines the volume of goods it sterilizes in a single cycle and is an important factor when choosing the appropriate unit for your facility. Small Capacity Autoclaves: Small capacity autoclaves, also known as benchtop or tabletop autoclaves, are compact and portable. With chamber volumes ranging from 1 to 45 liters, these units are suitable for sterilizing smaller instruments, glassware, and media. Due to their small footprint, they’re easy to integrate into tight spaces or to mount on countertops, making them a cost-effective and efficient solution for low-volume sterilization needs. Small autoclaves are commonly used in facilities where space and budget are limited, but reliable sterilization is necessary. Medium Capacity Autoclaves: Medium capacity autoclaves typically offer chamber capacities between 45 and 200 liters, providing greater flexibility for a wider range of applications. These autoclaves are often used in veterinary clinics, ASCs, and mid-sized research facilities, all of which require moderate throughput. Their larger capacity (relative to small autoclaves) allows for the sterilization of multiple instrument trays, wrapped materials, and even larger glassware or equipment in a single cycle, increasing efficiency and reducing downtime.They’re a versatile option, striking a balance between capacity and design, making them suitable for facilities with moderate sterilization demands without requiring the space or investment needed for large capacity autoclaves. Large Capacity Autoclaves: Large autoclaves, or industrial autoclaves, have capacities exceeding 200 liters and are built for high-volume, large-scale sterilization. These units are essential for hospitals, pharmaceutical manufacturers, and industrial facilities where large quantities of materials or oversized equipment need to be processed regularly. Large capacity autoclaves can accommodate large trays, bedpans, or bio waste containers, making them indispensable in high-demand environments.Large capacity autoclaves typically require a pit to be dug into the floor of the facility, enabling the autoclave chamber to sit at floor level, with drain plumbing located underground. This allows operators to wheel goods on carts or racks directly into the autoclave chamber. How to Choose the Right Type of Autoclave for Your Facility There are several things to consider when selecting the appropriate class, function, and size of steam sterilizer for your facility. Here are some best practices to help you start your search: Determine what types of loads you need to run. The materials you plan to sterilize will largely dictate what type of autoclave you need. For example, complex loads such as wrapped instruments, porous materials, and red bagged waste products will likely require a Class B sterilizer with vacuum functionality. Simpler loads such as solid metal instruments, empty glassware, and liquids can often be handled by Class N autoclaves.Additionally, facilities working with liquids, biohazardous materials, or waste will benefit from autoclaves with specific cycle options suited to these load types. Understanding your load requirements is crucial to ensure you select a model that can accommodate the diversity and complexity of your sterilization needs. Consider the layout of your space. Every autoclave requires dedicated floorspace; understanding how to manage that space is essential for optimizing your facility’s layout and performance. When determining what size autoclave you need, consider whether your plumber will connect from the back or side, as this impacts how much space you’ll need for maintenance access and could increase your autoclave’s overall footprint.You’ll also need to think about door placement: Do you have sufficient space to accommodate a door that swings outward, or do you need one that slides vertically? Ensure that there’s enough clearance so it doesn’t disrupt your workflow and decide on the door hinge’s placement based on your facility’s layout. Check your utility requirements. Autoclaves have specific utility demands, including water supply, electrical power, and steam. If your facility does not have an existing steam source — also known as “house” steam — you might consider an autoclave with a built-in steam generator. Be sure to verify that your facility can meet your new autoclave’s electrical requirements and that you can easily integrate water supply and drainage into the workflow. It’s also important to consult your facilities management team to ensure the property utility connections are in place before installation to avoid downtime or costly modifications. Evaluate your capacity and throughput needs. Start by assessing how many cycles you need to run daily and the anticipated size of each load. While small benchtop autoclaves may be sufficient for low-volume facilities, larger facilities will likely require medium or large capacity autoclaves to meet higher sterilization demands. Consider factors such as cycle time and load density, making sure to choose a unit that can handle peak loads without creating operational bottlenecks to avoid interruptions to your regular workflow. Plan for maintenance and service. Routine maintenance is key to keeping your autoclave running at peak performance levels and preventing unexpected downtime. When choosing a model, consider the availability of service plans and whether the sterilizer uses proprietary or easily sourced parts. Look for units from a manufacturer that offers strong support services and preventative maintenance options to ensure longevity. Think about customization and future growth. As your facility’s needs evolve, so may your sterilization requirements. Some autoclave models offer customizable features, such as programmable cycles, additional shelving, or specialized loading carts. A flexible autoclave that you can adapt for future use is a smart investment, so consider whether the model you choose can accommodate potential growth or more advanced sterilization requirements further down the road. For even more advice on how to choose the right type of autoclave for your facility, download our free buyer’s guide. How Do You Know Your Autoclave Is Actually Working? Completing a sterilization cycle isn’t the same as confirming that sterilization was successful. It’s important that your autoclave performs as validated, which requires a systematic approach to monitoring. According to guidance from the Centers for Disease Control and Prevention (CDC), effective autoclave monitoring relies on three types of indicators used in combination: Mechanical indicators are built into the autoclave itself and record the time, temperature, and pressure profile of each cycle via a printout or digital log. They confirm that the autoclave reached the correct parameters during the cycle but cannot confirm that those conditions were achieved uniformly throughout the load. Chemical indicators — typically autoclave tape, cards, or papers — change color when exposed to steam at or above the target temperature. They provide a quick visual confirmation that the load was exposed to heat but, like mechanical indicators, do not confirm that the temperature was maintained for a sufficient duration throughout the load. Biological indicators (BIs) are the most definitive verification method. They contain a standardized population of heat-resistant bacterial spores — which is why they’re also known as spore tests — specifically used to measure sterilizer efficacy. If the autoclave successfully kills all spores in the BI during a cycle, it confirms that the unit reached the required temperature and sustained that temperature long enough to achieve sterilization. BIs are incubated after the cycle, and any observed spore growth indicates a sterilization failure.The CDC recommends daily BI testing for autoclaves that run multiple loads per day. A failed BI test should prompt immediate investigation. Verify that the autoclave was used correctly, check time and temperature settings, inspect the steam supply, and contact the manufacturer if the issue cannot be resolved. Items processed since the last successful BI test should be quarantined and reprocessed. Full cycle validation — including installation qualification, operational qualification, and performance qualification — is required for BSL-3, BSL-4, and regulated pharmaceutical facilities. This process documents that the autoclaved was installed correctly, performs to specification, and continues to achieve validated sterilization outcomes over time. Explore Consolidated’s Full Line of Autoclaves Since 1946, Consolidated Sterilizer Systems have manufactured state-of-the-art steam sterilizers for laboratories, research institutions, healthcare facilities, and more. Explore our full line of autoclaves today: Single Door Hinged Autoclave Our single door hinged autoclave features a radial-arm hinged door designed for ease of use. It is available in 11 different chamber sizes ranging from 16” x 16” x 26” and 3.9 cu. ft to 24″ x 36″ x 72″ and 26 cu. ft and offers both gravity and pre-vacuum cycles. Suitable for small and mid-sized facilities, its stainless-steel construction and customizable control options deliver optimal sterilization for a wide range of applications. See Details Here > Single Door Vertical Sliding Autoclave Featuring a space-saving vertical sliding door, this autoclave is perfect for labs with limited space. Available in chamber sizes up to 26” x 26” x 49” and 19.2 cu. ft, it supports pre-vacuum and gravity cycles, ensuring flexibility for a wide variety of sterilizations needs. Delivering high-performance steam sterilization and ergonomic efficiency, including easy access and minimized operational footprint, this autoclave is ideal for mid-sized and large facilities alike. See Details Here > Double Door Pass-thru Autoclave Designed for cleanroom and biocontainment facilities, our pass-thru autoclave features dual doors for sterile transfers between separate zones. With chamber sizes of up to 24″ x 36″ x 72″ and 36 cu. ft, it’s capable of supporting large loads and efficient workflow management in highly regulated environments. See Details Here > Dual Chamber Tower Autoclave This space-saving autoclave stacks two chambers vertically to offer a 35% smaller footprint than traditional side-by-side models. Ideal for high-volume operations, it features independent chambers, allowing for simultaneous or staggered sterilization cycles. Available in chamber sizes of up to 20″ x 20″ x 38″ and 8.8 cu. ft, this unit supports efficient large-scale sterilization in limited spaces. See Details Here > To learn more about any of our units, contact our team today or request a custom quote. Frequently Asked Questions Q: What are the four methods of sterilization? A: The four methods of sterilization most commonly found in laboratory and healthcare settings are: Steam sterilization (autoclaving): The most widely used method because it is fast, effective against the full spectrum of microorganisms, and relatively inexpensive Dry heat sterilization: Uses hot air at high temperatures for longer exposure times and is appropriate for materials that cannot tolerate moisture Chemical sterilization: Uses agents such as ethylene oxide or hydrogen peroxide vapor and is intended for heat-sensitive instruments and devices Radiation sterilization: Uses gamma rays, electron beams, or ultraviolet light; primarily used in industrial and pharmaceutical manufacturing for single-use devices and packaging Q: What is a steam sterilizer, and how does it work? A: A steam sterilizer, or autoclave, uses high-pressure saturated steam to sterilize loads. At a high-level, the autoclave heats water to produce steam, which then penetrates the load and transfers heat energy. As the temperature rises, the heat denatures proteins in microbial cells, effectively killing bacteria, viruses, fungi, and spores. Steam sterilization is the more efficient and effective sterilization method, making it popular for laboratory, research, healthcare, and industrial applications. Q: What types of materials can be autoclaved? A: Autoclaves are highly versatile pieces of equipment that can be used to sterilize a wide variety of materials, including (but not limited to): Metal instruments Glassware and lab equipment Textile Red bag waste Biohazardous materials Autoclave-safe plastics Solid and liquid media Animal cage bedding Soil samples Q: Are there any materials that should not be autoclaved? A: Yes, certain materials should not be autoclaved due to their sensitivity to high heat, pressure, and moisture. These include: Heat-sensitive plastics Flammable or volatile chemicals Powders (which can be compromised by moisture) Electronics Some metals (which can corrode) Certain chemical agents such as chloride, which can damage the autoclave or produce hazardous gases Always consult the manufacturer’s recommended instructions for use to determine the autoclave compatibility of specific materials. Q: What are the different types of autoclaves available? A: Autoclaves are categorized by: Class, including Class B, Class N, and Class S Function, including vertical autoclaves, horizontal autoclaves, pass-thru autoclaves, hinged autoclaves, and tower autoclaves Capacity, including small capacity autoclaves, medium capacity autoclaves, and large capacity autoclaves Q: What are the different types of autoclaves available? A: The different types of autoclaves available are categorized by three variables: Class, which determines air removal method and load compatibility; these include Class B, Class N, and Class S Function, which determines physical configuration and workflow fit; these include vertical autoclaves, horizontal autoclaves, pass-through autoclaves, hinged autoclaves, and tower autoclaves Capacity, which determines how much you can sterilize per cycle; these include small capacity autoclaves, medium capacity autoclaves, and large capacity autoclaves Q: What are the three types of autoclaves? A: The three types of autoclaves, as classified by their air removal method, are: Class B autoclaves, which use a vacuum pump for complete air removal and can handle the full range of load types, including porous, hollow, and wrapped instruments Class N autoclaves, which use gravity displacement and are suitable for simple, solid, unwrapped loads Class S autoclaves, which manufacturer-defined specifications that often incorporate elements of both Class B and Class N autoclaves, making their exact capabilities variable Q: How do I determine which type of autoclave is best for my facility? A: To determine which type of autoclave is best for your facility, consider: Load types: Are you sterilizing solid instruments, porous materials, or liquids? Certain loads may require gravity or pre-vacuum cycles. Capacity: What is your anticipated daily throughput? Smaller models may suffice for low volumes, while large capacity autoclaves are a requirement for high-demand environments. Space constraints: How much available floor space do you have? Be sure to account for plumbing configuration and door clearance when determining what size autoclave you can accommodate. Utility availability: Consider water, steam, and electrical requirements, making sure to consult your facilities management team, before selecting an autoclave. Q: What is the difference between a Class N and a Class B autoclave? A: The primary difference between Class B and Class N autoclaves is how they remove air from the chamber prior to sterilization. Class B autoclaves utilize a vacuum pump to completely remove air from the chamber, which enables steam to better penetrate the load. Class N autoclaves use steam from a boiler or generator to create downward displacement, which pushes air out of the chamber. Unlike a Class B autoclave, a Class N autoclave does not guarantee 100% air removal. For this reason, Class B autoclaves are preferable for more difficult loads that contain porous or hollow materials. Class N autoclaves are suitable for most standard applications. Q: What is the difference between a gravity displacement and a pre-vacuum steam sterilizer? A: A gravity sterilizer is any sterilizer that uses the gravity displacement method for air removal. Gravity sterilizers perform what’s known as a gravity cycle to sterilize loads. A pre-vacuum sterilizer is any sterilizer equipped with a vacuum system — either a water ejector or a liquid ring vacuum pump — to ensure air removal from the autoclave chamber. Pre-vacuum sterilizers are used to perform what are known as vacuum (or pre-vacuum) sterilization cycles; pre-vacuum sterilizers can also run gravity cycles. Q: What is a steam flush pressure pulse autoclave? A: A steam flush pressure pulse (SFPP) autoclave uses alternating steam flushes and pressure pulses (rather than a mechanical vacuum pump) to remove air from the chamber. 17 Questions to Ask Before Buying Your Next Autoclave We created this 17-question eBook as a framework to help you explore and discover the exact type of autoclave best suited to your needs. Get eBook Tweet Like Share
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