IR Sterilization Oven

Mohamed Hossam Yahia Mohamed

Introduction:

Sterilization can be defined as a process which completely eliminates or kills microorganisms such as fungi, bacteria, viruses and prions. It can be used for many things such as equipment, food, surfaces, medications, and the most important field is the biological culture medium. Sterility is obtained by exposure of the substance that needs to be sterilized to physical or chemical agent for a fixed time. Various agents are used as a sterilizing agent such as liquid chemicals or gases, elevated temperature, ionizing radiation. The success of the sterilization process depends on choosing the suitable method for each substance. The bacterial spores are considered to be the most resistant among all of the living microorganisms because of their ability to resist the external damaging factors. Pathogenic and non-pathogenic microorganisms are destroyed by using whether chemical or physical processes yet these processes are not 100% efficient. Further processes need to be applied to have a maximum level of sterility to get sterile products. There are too many methods that can be used to make sure of the sterility level is reached. Here are some of these methods: steam, ethylene oxide, dry heat, micro waves, formaldehyde gas, hydrogen peroxide plasma, ozone gas, chemical solutions, ionizing radiations. The sterilization process requires the direct and complete contact of the sterilizing agent with the substance that need to be sterilized. The sterilizing agent has to be of a fixed nature to play its role effectively. Time is also important in the sterilization process to kill all the microorganisms found in the substances that need to be sterilized.

Heat Sterilization:

Heat sterilization is one of the most used methods on a large scale in the field of sterilization including the essential bacterial cell components and enzymes where higher heat temperature is required and oxidative changes take place. Heat sterilization can be used only on thermo stable products; however it can be used on moisture-sensitive materials for which dry heat lies in the range of 160 & 180 degrees and for moisture-resistant materials for which moist heat lies in the range of 121 & 134 degrees. The action of heat will be because of induction of lethal chemical events mediated throughout the action of oxygen and water.

Infrared Mechanism:

Infrared rays that lie in the waveband range of 0.8–15£ 10¡6 can be easily generated. With the help of an absorbent surface they are changed into sensible heat, producing high levels of increasing temperature the energy attack on the surface which is changeable into heat depends on the same geometric conditions as those used for UV lights. So, infrared radiation is the best to be applied to an even and smooth surface with vertical radiations. Infrared rays have been used to fix the internal phase of aluminum lids with a plastic coating on the external surface. Since the temperature increase can cause the plastic to soften, the maximum exposure time and temperature are limited. N.B. infrared rays can’t be used if there is an increase in temperature of the packaging substances because of infrared application and this leads to softening of the plastics.

Example of Infrared Sterilization Process:

Infrared rays cause sterilization by heat generation. Substances that need to be sterilized are placed in a moving conveyer belt and passed through a tunnel which is previously heated using infrared rays to reach a temperature of 180 degrees. The substances are exposed to that high temperature for a fixed time 7.5 minutes. The substances become sterile included glassware and metallic instruments. It is basically used in central sterile supply department. It needs special tools, thus is not applied in diagnostic laboratory.

Rapid Heating With IR Technology:

Infrared technology include fast heating that transfer energy at the speed of light taking the form of electromagnetic radiation without using any direct contact or transmitting media such as air, water, ..Etc. that reason is what makes IR sterilization suitable for sophisticated applications such as under clean room conditions and in vacuums.

IR Technology and the Product on the same Wavelength:

The emission behavior of an infrared lamp should be optimally adapted to fit the absorption rate of the substance being sterilized. A finely selected IR lamp ensures maximum heating and so the best results. Various physical standards of the substance being sterilized should be known before designing an IR system.

Types of IR Lamps:

In IR sterilization oven different types of lamps with different characteristics are used, depending on the ability of the substance to be dried or heated. The IR lamps used are classified according to the wavelength emitted

Application Example of IR lamps:

• Panel lamps: paint drying, preliminary gelation, Embossing equipment.
• Radiation frames in ovens: Heating-up zones, Post-curing of plastic coatings, Powder paint drying.
• Passage oven: Surface tempering of plastic pipes, Drying fibers at a high passage speed.
• Continuous oven: Rapid surface heating of product being treated, Preheating zone in combination with series-connected hot air zones.

IR Sterilization Advantages:

• IR emitters a great level in the heating rates and temperatures can be reached by using different wavelengths and densities.
• IR emitters can direct the energy to the required areas that needs treating.
• IR emitters are easy to switch on and off in a few seconds to suit the production requirements.
• IR is an energy source and it isn’t affected by the number of the components present in the oven.
• IR is a lot more compact, typically 1/4 to 1/3 the space.
• IR systems normally need low maintenance like changing filters or emitters.
• IR emitters with a high transfer of energy enable surfaces to be heated more rapidly to overcome conduction losses.
• IR emitters can be used to heat components in a vacuum chamber.
• IR heat is clean, no combustion products and no need to recirculate air.
• IR Infrared systems are custom designed to suit substrate being processed.

Types of IR Sterilization Ovens:

References:

Ansari. M & Datta. A. (2003), An overview of sterilization methods for packaging materials used in aseptic packaging systems, Institution of chemical engineering. 81(1).

Gary. E, Michael.J, Michael.E, & Roy.M. (1986), Effect of Sterilization by Dry Heat, American society of microbiology. 51(1), 39-43.

Patel, M (2003), Medical sterilization methods. USA: LEMO Inc.

Paula, R (2004), The Effects of different sterilization methods, Journal of bio medical materials research. 71(2), 268-277.