Autoclave: Definition, Components, Operation, Types, and Applications

Table of Contents

• Autoclave Definition
• Autoclave Parts/ Components
• a. Pressure Chamber
• b. Lid/ Door
• c. Steam generator/ Electrical heater
• d. Vacuum generator (if applicable)
• e. Wastewater cooler
• Autoclave Principle/ Working
• Procedure for running an autoclave
• Types of Autoclave

1. Pressure cooker type/ Laboratory bench autoclaves (N-type)
2. Gravity displacement type autoclave
3. Positive pressure displacement type (B-type)
4. Negative pressure displacement type (S-type)

• Uses of Autoclave
• Precautions

Autoclave Definition

A device known as an autoclave provides a physical way of sterilization by using steam under pressure to destroy bacteria, viruses, and even spores that are present in the material that is placed inside the receptacle. By heating the materials to a specified temperature for a set amount of time, an autoclave sterilizes the materials. The autoclave, which is also known as a steam sterilizer, is frequently used in healthcare institutions and other commercial settings for a variety of functions. Because it relies on moist heat treatment, the autoclave is regarded as a more efficient sanitation technique.

Autoclave Parts/ Components

The pressure cooker type or laboratory table autoclaves are the most basic types of autoclaves. The various elements and components of an autoclave are described in depth below:

a. Pressure Chamber

• A steam autoclave's pressure chamber, which consists of an interior room and an outer jacket, is its primary part.
• The outer compartment is made of an iron case, and the interior chamber is made of stainless steel or gunmetal.
• In order to speed up the time it takes to achieve the sterilization temperature, the autoclaves used in medical labs have an outer jacket that is filled with vapor.
• The items that need to be sterilized are placed in the interior compartment.
• The pressure container can be 100 L to 3000 L in capacity.

b. Lid/ Door

• The autoclave cover or entrance is the next crucial part of an autoclave.
• The lid's job is to isolate the sterilizer from the outside environment and maintain a clean environment inside.
• The asbestos washer and screw fasteners seal the top against airflow.

Other parts of the top include things like:

1. Pressure gauge

• An autoclave cover pressure indicator is present to show the pressure generated inside the autoclave during sterilization.
• The pressure indicator is crucial because it guarantees both the operation's readiness and the safety of the sterilizer.

2. Pressure releasing unit/ Whistle

• Similar to a pressure cooker, an autoclave has a bell on the top.
• By raising itself, the whistle releases a certain quantity of vapor, which lowers the pressure inside the cylinder.

3. Safety valve

• The autoclave's cover has a safety button, which is essential in situations where the appliance fails to function as intended or the pressure inside builds up suddenly.
• A thin coating of rubber covering the valve's interior bursts on its own to relieve pressure and prevent an explosion.

c. Steam generator/ Electrical heater

• Underneath the chamber is an electrical steam generator or boiler that heats the water and produces steam in both the interior and exterior chambers using an electric heating system.
• The amount of water in the interior compartment is crucial because if there is not enough water, there is a risk of the heating system burning.
• Similarly, if there is more water present inside the chamber than is required, it might conflict with the trays and other items there.

d. Vacuum generator (if applicable)

• Some kinds of autoclaves have a distinct vacuum generator that removes air from the interior of the chamber to produce a vacuum there.
• Different microbes may be able to thrive in the chamber because it has some air spaces. The pressure compartment is a crucial part of an autoclave because of this.

e. Wastewater cooler

• A common feature of autoclaves is a device for cooling effluent before it reaches the draining pipelines.
• Due to the boiling water being sent out of the autoclave, this method avoids any harm to the drainage line.

Autoclave Principle/ Working

• The autoclave uses the moist heat treatment method, in which the substance inside the cylinder is sterilized by steam applied under pressure.
• The high pressure raises the boiling point of water, allowing for a greater cleaning temperature to be reached.
• Under 760 mm of Hg of standard air pressure, water typically boils at a temperature of 100°C; however, the boiling point of water rises when the pressure is raised.
• Additionally, moisture in the vapor causes the coagulation of proteins, which results in a permanent loss of function and activity of microbes. High pressure also makes it easier for heat to quickly penetrate deeper layers of a substance.
• This theory is used in a sterilizer where the water boils at 121°C under 15 pounds of pressure.
• In an autoclave, where water boils at 121°C and 15 psi, or 775 millimeters of Hg, of pressure, this concept is used.
• This vapor emits latent heat when it comes into touch with the surface, which destroys the microbes.
• The wet destruction of the microorganisms is ensured by the condensed liquid.
• The air inside the compartment is released through the whistle once the sterilization process is finished (which will rely on the degree of contamination of the substance inside).
• The components inside the container then continue to heat up for a while as the pressure is then returned to the atmospheric pressure.

Procedure for running an autoclave

Typically, an autoclave runs for at least 30 minutes at a temperature of 121° C while using full steam at a minimum pressure of 15 psi. The procedures to be taken when operating a sterilizer are as follows:

1. It is advisable to inspect the autoclave for any remnants of the prior operation before using it.
2. After that, the compartment is filled with enough water.
3. The container is now filled with the items to be disinfected.
4. Following the closure of the cover and tightening of the fasteners to ensure airtightness, the electric heater is turned on.
5. To keep the necessary pressure in the chamber, the safety valves are changed.
6. When the water inside the chamber reaches a rolling boil, the air-water combination is permitted to pass through the discharge conduit, dislodging all of the air inside. When the water bubbles stop coming out of the conduit, the full displacement can be assured.
7. The drainage pipe is then sealed, allowing the internal steam to build to the appropriate amounts. (15 lbs in most cases).
8. The whistle sounds to release extra pressure from the chamber once the desired pressure has been achieved.
9. The autoclave runs for a holding time after the buzzer, which is typically 15 minutes.
10. The autoclave is now permitted to cool and the electric heater is turned off once the pressure gauge shows that the internal pressure has reached atmospheric pressure.
11. After that, the output line is released to let outside air into the autoclave.
12. The lid is then lifted, allowing the sterilized items to be removed from the compartment.

Types of Autoclave

There are several different types of autoclaves available on the market, including:

Pressure cooker type/ Laboratory bench autoclaves (N-type)

• There are still many places in the world where people use these as household pressure cookers.
• A rubber gasket can be used to attach and close the more contemporary version, which has a metal compartment with a secure metal top.
• It has a safety valve, pressure monitor, and a tap for steam and air release. At the bottom of the container is an electric immersion warmer.

Gravity displacement type autoclave

• This is the sterilizer that is most frequently used in labs.
• In this kind of autoclave, the heating device creates steam inside the chamber, which circulates throughout the room for sterilization.
• Comparatively speaking, this kind of sterilizer is less expensive than others.

Positive pressure displacement type (B-type)

• In the case of this type of autoclave, the steam is produced in a different steam generator and then introduced into the autoclave.
• This autoclave is quicker because the steam can be produced in just a few seconds.
• Compared to gravity displacement autoclaves, this variety is an upgrade.

Negative pressure displacement type (S-type)

• A steam engine and a vacuum generator are both present in this kind of sterilizer.
• Here, the steam generator produces steam while the vacuum generator removes all of the air from the sterilizer.
• The sterilizer is then filled with vapor.
• This autoclave variety is the most frequently advised because it is highly accurate and gets a high degree of sterility guarantee.
• This form of autoclave is also the most costly.

Uses of Autoclave

Since materials holding water cannot be sanitized using dry heat sterilization, autoclaves are crucial tools to guarantee the sterilization of those materials. Additionally, autoclaves serve a number of other functions.

1. They are used to sanitize scientific equipment, sterilize media, and decontaminate particular biological debris.
2. Before disposal, it is advised to autoclave regulated medical debris that may contain germs, viruses, and other biological materials.
3. Autoclaves are used in medical laboratories to sterilize medical waste, glassware, surgery instruments, and equipment.
4. Similar to this, pipette tips, plastic tubes, autoclavable receptacles, and growth media are all sterilized in autoclaves.

Precautions

Although autoclaves are fairly easy to use, there are a few guidelines and safety measures that must be taken. Following some crucial safety measures when using a sterilizer includes:

1. Autoclaves should not be used to sterilize water-proof or water-resistant things like grease or powders.
2. The materials should be put into the autoclave so that the steam can reach all of the objects inside without overcrowding it.
3. Always put the things to be autoclaved in a secondary receptacle.
4. To autoclave packaged refuse, only autoclavable containers are permitted.
5. Articles should be covered in materials that allow for steam entry in order to guarantee adequate penetration; materials like aluminum foil should not be used.
6. The chamber's top or sides shouldn't be touched by the objects that are put inside.
7. Separate autoclaving should be done for the clean objects and residues.
8. Never try to access the cover of the autoclave while it is running.
9. Never autoclave liquid components in enclosed vessels.
10. To avoid spilling the liquid, only two thirds of the capacity of the receptacles should be filled with the liquid.
11. You shouldn't use plastic or polyethylene plates or receptacles because they could melt and harm the sterilizer.
12. Additionally, never microwave tissue with paraffin imbedded in it, domestic chlorine, or any other flammable, reactive, poisonous, or radioactive materials.
13. Being a flammable material, paper shouldn't be put immediately inside an autoclave. To avoid a conflagration, it should be autoclaved in a waste bag using the bio bag option.