What Is an Autoclave?

Autoclaves are often found in laboratories.

Autoclaves are devices that are designed to sterilize a variety of lab equipment and media for growing lab cultures. Autoclaves are also used to sterilize medical tools and piercing equipment. Their primary purpose is to rid items and liquids of any and all bacteria and contamination by using a combination of high heat and high pressure.

Significance

Bacteria and contamination can have serious consequences in labs and in medical settings. Bacteria in cell media can quickly kill off any cultures that are feeding on the media, and bacteria can be deadly to patients or those getting piercings by causing infections. Autoclaves greatly reduce these risks by killing all life forms on items placed inside them.

Features

An autoclave is a large steel device with a sealed inner compartment. When the compartment is filled with medical utensils, beakers filled with media and other biohazard waste to be sterilized, high pressure steam fills the chamber.
The autoclave has a network of steam valves and tubes inside the compartment that pump in water that is boiled into steam form. The door of the compartment creates an airtight seal that increases pressure. The combination of pressure and extreme heat makes it impossible for bacteria to survive. Temperatures can rise above 130 degrees C inside.

Operation

Technicians fill the bottom of the autoclave compartment with a small amount of water. Large heavy-duty lab tubs are then filled with items to be sterilized. Loose items such as scalpels and tweezers are sometimes placed in approved plastic autoclave bags and sealed.
Liquids such as nutrient media and distilled water are placed in Pyrex beakers with the tops covered loosely with tin foil. Biohazardous waste is placed in approved plastic autoclave bags and sealed. Usually the technician will only put one type of load into the autoclave at a given time--for example, only lab utensils might go into one load and beakers into another. The door is then shut and locked, and the autoclave timer and temperature is set.

Time Frame

The amount of time that items need to be sterilized varies. For unwrapped items and empty beakers, 15 minutes is usually sufficient. For wrapped items, bagged items and filled beakers, 20 to 30 minutes is needed. Beakers with over 2l of liquid need around 40 minutes, and biohazard materials need at least 60 minutes.

Warning

Autoclaves can be extremely dangerous to use. When using an autoclave, do not adjust the pressure or temperature settings, as these should be set and maintained by a lab staff member. When using an autoclave, always wear heat-resistant gloves, a lab apron and protective goggles.
When opening an autoclave, wait at least 15 minutes after a cycle has ended before unlocking the door. Wait until the pressure gauge reads "0." The vacuum seal created can cause the door to blast off the unit or hot steam to rush out. Slowly open the door to let any leftover pressure out after waiting for the unit to cool down. Never remove items using your bare hands, as items will be very hot.

References

• What Are Autoclaves?
• Autoclave Safety