Autoclave-Related Blog Postings

What is an Autoclave?

An autoclave, also known as a sterilizer is a piece of equipment that is used to sterilize various instruments, as well as solids and liquids, including biological waste matter. Autoclaves are frequently used in industrial settings, medical/dental facilities and laboratories, as well as public facilities including aesthetic salons, tattoo parlors, and veterinary practices.  Autoclaves are used chiefly for sanitary and quality control purposes to prevent contamination by bacteria, spores and other micro-organisms, some of which may be resistant to detergents and other sterilizing solutions. ue to the wide range of applications, autoclaves vary in shape, size, and functionality, however, the basic mechanism of using high heat, steam under high pressure is fundamentally similar.

How Autoclaves Work

Items that are meant to be sterilized are placed within the autoclave’s sealed chamber and are subjected to high pressure steam (ranging from 105-135°C) for a given amount of time. Autoclaves are designed to allow heat and pressure to build within the chamber and are equipped with safety mechanisms to contain and release pressure to maintain safe levels. Autoclaves are usually equipped with temperature and timer controls to allow users to set the proper setting for any given autoclaving application.

Types of Autoclaves (Gravity vs. Vacuum Autoclaves) and Their Advantages

Types of Autoclaves

Autoclaves function primarily through either gravity or vacuum-induced or pre-vacuum (prevac) sterilization methods, though some types of autoclaves combine both methods to sterilize.  Though both types of autoclaves sterilize through high temperature steam and use pressure as a means to allow steam to displace ambient air in the chamber to penetrate sterilization media, the means by which these mechanisms occur differ and thus, are more conducive to

Gravity autoclaving, also known as gravity displacement autoclaving is the most basic form and is suitable for sterilizing the most common laboratory media, including steel utensils, glassware, and bio-hazardous waste. Gravity-induced autoclaving involves pumping steam into the autoclave chamber, which displaces the ambient air and forces it out of exhaust valves, so that the remaining steam can sterilize the contents. This mechanism is advantageous in the simplicity of its design and lack of dependency on peripheral mechanisms to displace ambient air with steam, making these types of autoclaves more affordable and dependable.The majority of autoclave media, or items to be sterilized are simple in design and do not contain spaces or obstacles for steam to penetrate within, thus the steam displacement function is ample for proper sterilization. It is for these reasons that gravity autoclaves are the most common types of autoclaves in the market and are usually the recommended type of autoclave for most uses.

On the other hand, vacuum autoclaving, also known as pre-vacuum autoclaving or sterilizing is more suited in cases where air cannot be easily removed from sterilization media.  This may include large or porous items such as animal cages and bedding sterilization as well as wrapped surgical kits. The vacuum function in these autoclaves allows deeper sterilization of the contents, as it completely evacuates the ambient air within, allowing high-temperature steam to penetrate and sterilize areas that would normally be occupied by ambient air, and can be more efficient at sterilizing certain items with hard-to-reach areas within.

Autoclave Media and the Appropriate Autoclave Type

As mentioned above, your choice of an autoclave system largely depends on your autoclave media, ie. the items to be sterilized. Overall, steam sterilization is highly dependable, effective, fast, and non-toxic, and offers an inexpensive way to rapidly heat and penetrate the chamber’s contents, including appropriately contained liquids. However, this method cannot sterilize powders or oils, and can only work with heat and moisture-resistant goods. Keeping this in mind, below is a summary of the primary types of media used by gravity and vacuum-autoclave types.

Gravity autoclaves are appropriate for sterilizing non-porous items (i.e. those with a hard surface):

• Most metals, particularly stainless steel surgical instruments and lab utensils
• Polypropylene Pyrex® or Type I borosilicate glassware
• Biohazard waste
• Unwrapped goods

Vacuum (pre and post) are appropriate for sterilizing large or porous items:

• Media solutions in appropriate containers, such as tissue culture flasks with loose caps for a steam autoclave cycle
• Pipette tips and other high-density polyethylene products, such as syringes
• Wrapped dry items that can trap air
• Animal cages and bedding

Choosing an Autoclave

Choosing the right autoclave for your purposes requires you to not only assess the type of media to autoclave, but also throughput capacity, available lab space, and access to utilities including electricity (with proper power output), water and house steam.

Due to the simplicity of the gravity-displacement mechanism, which requires an autoclaving chamber, a heating mechanism, intake and exhaust valves, there is great flexibility in design for gravity autoclaves, including front and top-loading types.

The top-loading type autoclave is particularly advantageous, as it allows for maximum loading space, minimum floor space requirement and does not require a any building steam connection, as the vertical chamber design allows for water to rest at the bottom, which in turn is turned into steam through a heating element located at the bottom.Note that many autoclaves on the market, especiallycompact top-loading autoclavesoften require no more than access to the proper electrical outlet type and enough space to place your autoclave.

Gravity autoclaves are also particularly advantageous when used in geographical areas of high humidity or higher altitudesas they consistently retain the relationship between pressure and heat within the autoclave chamber and overcome differences in boiling points at higher altitudes by opening and closing the exhaust valve. Known as high altitude autoclaves, their functions allow for proper sterilization to occur in laboratories and hospitals located in markets with high altitude terrains.

Regarding the size of your autoclave, in order to limit energy use and costs especially for smaller labs, it is important to buy the proper size autoclave that will accommodate the equipment that needs sterilizing, while not going over capacity. For this there are several autoclaves that range between 50 L and 70 L, which tend to strike a good balance between relatively high capacity and low energy use.

For more information on autoclaves that may be the right match for your laboratory, please have a look at information on the Tomy SX-Series Autoclaves.

Autoclave Maintenance- Proper Usage and Cleaning for Autoclave Performance and Longevity

Operating instructions and preventative maintenance

Though autoclaves, sometimes referred to as steam sterilizers, are pieces of equipment that designed to disinfect and sterilize laboratory media (glassware, plasticware, etc.) as well as biohazard waste, they themselves must be maintained and used in a way that allows them to properly function and be suitable for long-term use.  This is especially true of steam sterilizers or gravity autoclaves, which heat water to extremely high temperatures up to 135° C and subject media (and the autoclave sterilizer itself) to high temperature and pressure.  Because of these volatile conditions under which autoclave sterilizers operate, maintenance includes using the proper type of water with your autoclave, autoclaving in a way that prevents media spilling into your autoclave and regularly changing the gaskets, all of which maximize sterilization ability and extend the lifetime of your autoclave.

It’s something in the water (or the water itself)

One of the first priorities when operating autoclave sterilizers that use steam is to use the proper type of water. The most plentiful, cheap and easy-to-access source of water is tap water, however, the high mineral content of tap water in many areas can cause problems for your machine. In many parts of the United States, tap water contains a high mineral content including lime, which can calcify and leave residue on the autoclave heater and inside the chamber, leading to permanent and irreversible damage, especially of the heating unit, which is central to the sound operation of the autoclave. For water mineral content (hardness/alkalinity) by area in the United States, please visit this page.

In order to prevent the problems caused by high mineral-content water, autoclave sterilizers that use steam should be operated with DI water, which stands for De-Ionized water and is also referred to as Demineralized Water.This type of water can either be purchased or created by de-ionizing tap water using special equipment found in most laboratories. Though they are often confused with one another and sometimes used interchangeably, please note that DI water is not the same as Distilled Water, as they are created using different processes and can change the outcome of experiments depending. More information on the differences can be found here.

In the case of Tomy SX-Series autoclaves, DI water with a small amount of tap water should be used, as the water sensor works by detecting ions in the water, as opposed to water itself. Please fill the autoclave chamber with enough DI water to cover the heater (up to the bottom plate inside the chamber) and submerge the water level sensor (small metal knob that protrudes from on the inside of the autoclave chamber), adding a small amount of tap water to make sure that the water sensor can detect ions. For SX-500 model autoclaves add approximately 50 mL of additional tap water to the DI water, for SX-700 model autoclaves add 100 mL of additional tap water to achieve the proper mix.

Cleanliness is next to…

Autoclaves should be drained and cleaned at least once a month, as another source of damage to autoclaves, especially autoclave heaters, is dirty water that sits in the autoclave chamber.  At high temperature and pressure, impurities that get into the water from autoclave media can stick and burn to the autoclave heater, preventing the heater from transferring heat and permanently damaging it, potentially rendering your autoclave obsolete.For Tomy SX-Series autoclaves, water in the autoclave chamber can be drained by removing the white plug and opening the drainage valve (green handle) under the machine and draining this into a container for disposal. For biohazardous material and water disposal, especially for BSL (Bio Safety LeveL) 2 and above laboratories, please contact the Center for Disease Control or the relevant national authority for disposal instructions.

Bucket and Tall Basket with Solid Bottom to prevent spilled media from contaminating chamber water

In addition to draining water from the autoclave chamber, the inside of the autoclave needs to be wiped out and the heating element should be thoroughly cleaned.For Tomy SX-Series Autoclaves, the heating element can be accessed by removing the bottom plate inside the chamber. To maintain performance and increase the longevity of your machine, we also recommend periodically removing any reside that builds up inside the chamber, especially on the heating element. For the type of cleaners that we recommend, please contact us here or via email at tomy@amuzainc.com.

Another important method for keeping your autoclave clean is to prevent autoclave media from spilling or boiling over into the water in your machine in the first place. If using open bottles of culture media or other types of solutions, please use the bucket type inserts or solid bottom tall baskets (as opposed to the standard baskets that come with your machine), to prevent solutions from overflowing into chamber water and sticking to / burning onto the heater unit.

Changing the gasket

Keeping the lid gasket, also known as an autoclave door seal, etc. in top condition is key to keeping your autoclave in proper working condition, which also ensures proper sanitization for autoclave media and laboratory safety. When autoclaving, the gasket is subject to high temperature and pressure, which can cause cracking and lead to leaks in the autoclave and will prevent the autoclave from achieving the necessary temperature and pressure for sterilization, as well as lead to other problems and damage to your autoclave.

The recommended time for replacing the lid gasket is 3 years or less, especially if the autoclave is used frequently and is constantly subject to the high temperature and pressure of autoclaving. If using a Tomy SX-Series Autoclave and are due for a replacement, contact us here and refer to the following Tomy autoclave lid gasket models / part numbers:

• Tomy SX-500 Autoclave Lid Gasket (Part #T02.015.00)
• Tomy SX-700 Autoclave Lid Gasket (Part #T02.016.00)
• Tomy ES-215 Autoclave Lid Gasket & Washer Assembly (Part # 078.01)
• Tomy ES-315/SS-325 Autoclave Lid Gasket & Washer Assembly (Part # 079.01)

Next Steps

As laid out above, no matter what you use your autoclave sterilizer for, using the proper type of water, the proper buckets and baskets for autoclave media and regular maintenance including changing your autoclave gaskets can both prevent damage to your autoclave and give it the proper treatment for long-term use.

If you have any questions regarding any of the points outlined above, or need to purchase replacement gaskets for your Tomy autoclave, please email us at tomy@amuzainc.com, call us at 858-800-3900 or contact us using the Tomy Amuza site contact form.

High Altitude Autoclave Sterilization

According to the WHO Laboratory Safety Manual (3^rd Edition, p27), autoclaves are essential laboratory equipment for the disinfection and sterilization of tools and biohazard products. However, sterilizing at higher altitude geographical locations with an autoclave presents special issues. Due to the increased pressure and lower boiling points of higher altitude areas, a high-altitude autoclave, ie. an autoclave that is programmed to accommodate the relationship between pressure and the various state of gases and liquids at various altitudes must be used. In fact, high-altitude reprogramming is necessary for all autoclaves when operating at 1,200m or more above sea level, which can inevitably lead to improper sterilization and safety issues.

Saturated steam can be produced at temperature and pressure levels where water and steam can coexist, which also includes high altitude areas. Autoclaves that are programmed to control the three elements of steam sterilization–time, humidity, and temperature maintain a constant relationship between pressure and temperature, ensuring that no imbalances that would significantly affect the sterilization process.  This mechanism is combined with the system’s automatic fine exhaust adjuster ensures that the pressure and temperature levels can be maintained, ensuring the proper conditions for sterilization and the elimination of microorganisms.

Boiling points differ at high altitudes too, which can affect a normal autoclave’s electric valve and prevent the chamber’s pressure from rising, which causes sterilization failure. The unique automatic fine exhaust of this system will detect the temperature and pressure. If the temperature/pressure balance is skewed, the system will exhaust residual air to maintain saturated steam close to an equilibrium state in the chamber and create a reliable sterilization environment.  By adjusting the exhaust valve opening and closing temperatures, the differences in altitudes and boiling points can be controlled for and the appropriate temperature and pressure rises can be secured with this high-altitude autoclave.

In summary, when purchasing an autoclave for use in a high-altitude environment, it is necessary to purchase a model designed for high altitude use. These models are programmed in such a way that pressure and temperature relationships can be maintained in a particular high-altitude area (programming varies according to altitude and atmospheric pressure).

Tomy offers high altitude reprogramming starting at models used for altitudes exceeding 1,000 meters above sea level. If you are interested in learning about Tomy autoclave high altitude reprogramming, please use our contact form or reach out to a Tomy representative at tomy@amuzainc.com.