Moist Heat Autoclave Precautions

Moist heat, or steam heat, is the most effective method of sterilization, or eliminating microorganisms. An autoclave uses moist heat within a cylinder to sterilize medical instruments. The autoclave is also used to sterilize biological waste before it is disposed of; the level of steam produced within the autoclave causes coagulation of protein materials and results in irreversible damage to cells.

How It Works

• In order for a moist-heat autoclave to properly sterilize, the temperature inside the cylinder must be 121 degrees centigrade or higher. The time required to properly sterilize an instrument is at least 30 minutes. The total time needed depends on the items being sterilized and is reached when all instruments in the cylinder have reached the appropriate temperature and steam has contacted all instruments. When the sterilization process is complete, indicators on the autoclave change color. Steam from the autoclave permeates paper, fabric and cardboard.

Using Paper Bags

• Steam-permeable paper bags are used inside the autoclave to enclose reusable items. Before steaming, the bags are folded and taped closed. After sterilization, items remain in the bags until their next use.

Using Biohazard Bags

• Plastic biohazard bags are used to sterilize biological waste before it is disposed. Biohazard bags are placed in stainless steel pans to retain draining liquid. Since biohazard bags are not steam-permeable, they must be left partially open to allow steam to penetrate the bags. Water is sometimes placed inside the bag to increase the steam; however, water is not added if there is a possibility of biohazardous materials splashing outside of the bag.

Sterilizing Without Bags

• Sometimes reusable instruments are sterilized in the autoclave without a bag. When this occurs, any tubular or conical instruments must be plugged with cotton wool to keep the interior of the instrument sterile after the process. Mesh baskets are used for small instruments. All lids are loosened to prevent explosion.

Precautions

• If steam does not reach all items in the autoclave, the sterilization process will be incomplete. Personnel must be careful to fill the autoclave only with the recommended number of instruments so that moist heat permeates throughout the cylinder. When using the autoclave, wear a lab coat, safety glasses and gloves that resist heat. The autoclave must be opened slowly after the steam cycle to prevent burns and glass breakage, allowing steam to escape before you attempt to completely open the cylinder. An autoclave is not intended for solvents, radioactive material or any volatile or corrosive chemicals. Do not attempt to clean a spill inside the autoclave before the cylinder is completely cooled. Never use your bare hands to retrieve broken glass. Sharp objects can poke through an autoclave bag and cause a needle-stick injury. For this reason, all sharps should be placed not in the autoclave but in an appropriate disposal container. Autoclave bags should be lifted out of the cylinder by the tops of the bags. Steam sterilization can make sharp edges blunt. Steam does not penetrate oil, grease or powder materials.

Testing the Autoclave

• Biological indicator test kits for the moist-heat autoclave are available on the market. These indicators contain bacterial spores that test the competency of the autoclave. These should be used at regular intervals. The device must also be maintained by a manufacturer-certified technician.