Microbiology and clinical laboratories constantly deal with infectious materials that should be adequately disinfected, sterilized, and disposed of. Heating under a Bunsen burner is the preferred method of sterilizing the metallic part of the inoculating loop and wire. Sudden splatters while heating under the burner can create aerosols with viable organisms, contaminating the working area. A bacterial incinerator is a possible substitute for sterilizing the loops and wire.
A bacterial incinerator is laboratory equipment that uses heat produced by infrared rays for sterilizing waste materials generated during laboratory procedures. A micro or bacterial incinerator is also helpful for sterilizing metals like a needle and lancet.
Parts of Micro Incinerator
The bacterial Incinerator or micro incinerator has the following parts:
- Base: It is the area that helps place the equipment on the benchtop. It is usually made up of plastic or epoxy resin.
- Loop holder: The base of some incinerators has a loop holder present. It helps in placing a sterilized loop after incineration.
- Switch: It helps turn on the incinerators and is present in the base.
- Barrel: It is the area where the heating occurs. The outside is covered with a grid of stainless steel. The internal part is made up of a quartz tube and has an electric element thermally insulated with ceramic fiber. It has an opening for inserting the inoculating loops and wire.
- Arm: It connects the base and the barrel and is made up of similar material as the base. The arm is adjustable to have a correct angle for heating.
- Electric wire: It is at the base of the micro incinerator and provides electric current for operating the equipment.
Principle of Micro Incinerator
The micro incinerator is based on the incineration principle (destruction by burning), where heating metal objects and organic matter is performed in the absence of oxygen. The quartz tube (internal part of the barrel) is heated by the infrared rays provided by the electric element in the barrel after connection to the electric source. The temperature inside the barrel is enough to incinerate the metal loop and needles. Since the barrel is closed from all sides, the aerosols generated during sterilization encloses and disposed of inside the barrel. This enclosure prevents aerosols from coming in contact with other surfaces.
Operating the Bacterial Incinerator
The bacterial incinerator is used for heat-fixing the slides and sterilizing inoculating loops and needles. Its operation is more effortless and requires very little time.
Steps for sterilizing the loop in the bacterial incinerator
- Turn on the incinerator before 5-10 minutes of use.
- Then place the inoculating loop or needle (the wire part) inside the open end of the barrel for about 20-30 seconds. The loop appears red-hot.
- After that, bring out the loop and let it sit for 10-20 seconds before use to avoid killing the desired microorganism.
- Finally, sterilize as mentioned above after each use.
Steps for heat-fixing smears in the bacterial incinerator
- Turn the bacterial incinerator on before 10 minutes of operation.
- Then, place the slide with air-dried smear in the slide holder tray.
- After that, place the tray in the open end of the barrel for 10 seconds.
- Finally, the smear is heat-fixed and ready to be stained.
Things to consider
- The bacterial incinerator should be switched on 10 minutes before heating.
- Inoculating loop and wire should not touch the internal part of the barrel because it can melt anything that touches it.
- Slides should be held using slide trays instead of directly by hand. The smear should face the holder, and heat should be provided on the opposite side of the smear.
- The outside of the barrel heats up, so one should avoid touching the barrel while using the micro incinerator.
- Only the wire portion of the loop/needle should be inside the barrel and not the whole loop so that the burning of the hands of the operator is prevented.
Types of Bacterial Incinerator
The basis for the types of the bacterial incinerator is temperature. The most common type of bacterial incinerator can reach the highest temperature of 850℃. Likewise, the temperature ranges from as low as 800℃ to as high as 900℃.
Uses of Bacterial Incinerator
The bacterial or micro incinerator is used in microbiological laboratories to limit aerosol formation. The following are the detailed uses of micro incinerators:
- Safer microbial culture transfer: The inoculating loop and needle used to transfer bacterial cultures need to be adequately sterilized. Using a Bunsen burner or open flames may create an aerosol that can contaminate the working area. So, using a bacterial incinerator help contain the aerosols inside the barrel. This containment helps safely transfer the culture from one tube to another.
- Heat fixing the smear in the slides: The bacterial incinerator has slide-holding trays. It helps in heat-fixing smears in the slides for staining.
- Sterilization of the mouth of the tube: Introducing the open end of the cultural tube in the open part of the barrel for 10 seconds helps sterilize the mouth of the tube. It is a similar process to using a Bunsen burner for sterilizing.
Advantages of Bacterial Incinerator
The advantages of bacterial incinerators are as follows:
- A micro incinerator is a perfect substitution for open flames like Bunsen burners and alcohol lamps.
- It requires very little time, i.e., 5-7 seconds, and at high temperature (850℃).
- It is safe to use as no open flaming is required.
- The equipment is small and can fit on a benchtop. The setup of a micro incinerator is also easy.
- It has a longer lifespan.
- It is electrical, so the consumption of fossil fuels is significantly less.
Difference between Incineration and Combustion
Although both incineration and combustion use heat or the method of burning, both have many differences. Incineration is the destruction of materials, whereas combustion is the reaction of oxygen and materials to produce energy. Likewise, incineration can occur without oxygen, but combustion requires oxygen. The final products of incineration and combustion are also different; combustion releases heat energy, water, and carbon dioxide, but incineration releases fuel gas, heat energy, and ashes.
The heating of substances, usually waste materials, in the absence of air for proper disposal is known as incineration. It generates ash, fuel gas, and heat as the final product. It is primarily used in waste disposing plants.
The heating of substances in the presence of air is known as combustion. It generates carbon dioxide, heat, and water as the final product of complete combustion. In case of incomplete combustion, carbon monoxide is released instead of carbon dioxide. It is used for generating fire in industries.
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