Demonstrate the working/SOP of autoclave.
Autoclave: is a specialized piece of equipment designed to deliver heat under pressure to a chamber, with the goal of decontaminating or sterilizing the contents of the chamber. The autoclaving process is typically used to destroy microorganisms and disinfect labware, equipment
Limitations of Autoclaves- Although autoclaving is an economical and environmentally friendly way of sterilizing and decontaminating items, not all materials can be autoclaved. In fact, some materials present specific hazards if autoclaved. DO NOT autoclave the following items: Chemicals (includes most disinfectants, e.g. bleach) Radioactive material Some plastics – ensure materials are autoclavable.
Uses of Autoclaves Items that CAN be autoclaved include- but are not limited to: Cultures and stocks of infectious material Culture dishes and related devices Discarded live and attenuated vaccines Contaminated solid items such as: petri dishes, pipettes, gloves, paper towels, lab coats, solid and liquid waste Items for sterilization such as: glassware, media, liquid solutions Some equipment -ask supervisor for confirmation.
Autoclaves Working Principle:
Autoclaves use pressurized steam as their sterilization agent. The basic concept of an autoclave is to have each item sterilized -whether it is a liquid, plastic ware, or glassware- come in direct contact with steam at a specific temperature and pressure for a specific amount of time. Time, steam, temperature, and pressure are the four main parameters required for a successful sterilization using an autoclave.
The amount of time and temperature required for sterilization depends on the type of material being autoclaved. Using higher temperatures for sterilization requires shorter times. The most common temperatures used are 121 C and 132 C. In order for steam to reach these high temperatures, steam has to be pumped into the chamber at a pressure higher than normal atmospheric pressure.
Now that we have covered the basic principle of how autoclaves use pressurized steam to sterilize contaminated materials, we will now go over how autoclaves operate.
Autoclave Design Diagram & Parts
Similar to pressure cookers, steam sterilizer autoclaves work quickly and effectively because of their high temperature. The machine’s temperature and unique shape make it easier to hold the heat inside much longer. The autoclave also does a great job of efficiently penetrating each piece of equipment. The autoclave’s chambers are usually in the shape of a cylinder because cylindrical shapes are more equipped to handle the high pressure that is needed for the sterilization process to work. For safety reasons, there is an outside lock and a safety valve that prevents the autoclave steam sterilizer’s pressure from getting too high.
Once you close the autoclave sterilizer chamber, a vacuum pump removes all the air from inside the device or it is forced out by pumping in steam. If done the first way, the sterilizer is pumped with high pressured steam to quickly raise the internal temperature. On every autoclave there is a thermometer that is waiting for the thermal sweet point, 268-273 degrees Fahrenheit, and then it starts its timer. During the sterilization process, steam is continuously entering the autoclave to thoroughly kill all dangerous microorganisms. Once the required time of sterilization has elapsed, the chamber will be exhausted of pressure and steam allowing the door to open for cooling and drying of the contents.
Mode of Action Autoclave Sterilizers:
Moist heat destroys microorganisms by the irreversible coagulation and denaturation of enzymes and structural proteins. In support of this fact, it has been found that the presence of moisture significantly affects the coagulation temperature of proteins and the temperature at which microorganisms are destroyed.
Autoclave Working – Operation:
Place containers in the autoclave.
Check the strainer to see if it is clogged. The strainer is located on the bottom of the chamber near the door. The autoclave will not come up to pressure if the strainer is clogged.
Close the door. For the SMALL autoclave, rotate the handle clockwise until it is snugly closed. For the LARGE autoclave, rotate the small, inner handle clockwise first until it locks. Then rotate the large outer handle clockwise until it is snug.
Open the glass-faced door in the upper right corner. Set STERILIZE time and, if needed, set DRY time.
Select the SETTING you want by pushing in the colored button.
Push in the RED button to turn the autoclave on.
Wait until the temperature reaches 121°C and the RED sterilization light in the glass-faced box turns on before recording the Chamber Pressure on the Log. The chamber pressure should be 16-20 psi once the sterilization cycle starts. Anything below 16 psi should be reported to your lab manager.
At the end of the run, ensure the CHAMBER PRESSURE has returned to ZERO before attempting to open the door. The FLUIDS cycle takes much longer than FAST EXHAUST – be patient. If the door cannot be easily opened, WAIT 10 minutes before trying again. If you wrench on the door and attempt to force it open, the internal metal rod that connects to the door handle will twist from the pressure.
To open the door:
SMALL autoclave: rotate the handle counterclockwise. Be careful, steam burns! Step to the side and crack open the door. Allow the steam to escape from the chamber then open the door and remove your items.
LARGE autoclave: First rotate the LARGE OUTER handle counterclockwise until it is loose. Next, rotate the SMALL INNER handle counterclockwise until the door opens. Be careful, steam burns! Step to the side and crack open the door. Allow the steam to escape from the chamber then open the door and remove your items.
As a courtesy to others needing to use the autoclave, promptly remove your items when the cycle is completed and you can easily open the door. Wear protective, heat resistant gloves when removing items.
Autoclaved waste materials are to be taken directly to the dumpster for disposal. Orange autoclave bags must be put into black trash bags before disposing in the dumpster.
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