Dry Heat Sterilization-Ovens

May 2nd, 2014 by Acmas Leave a reply »

Sterilization is the process of complete removal/destruction of the entire viable microorganism or Sterilization can be defined as any process that effectively kills or eliminates transmissible agents (such as fungi, bacteria, viruses and prions) from a surface, equipment, foods, medications, or biological culture medium.

Various methods used for sterilization are Heat (Dry and Moist), Radiation, chemical compounds and gases etc.

  • Moist heat sterilization is the most efficient Biocidal Agent. In the pharmaceutical industry it is used for Surgical dressings, Sheets, Surgical and diagnostic equipment, Containers, Closures, Aqueous injections, Ophthalmic preparations and Irrigation fluids etc.
  • Dry heat sterilization can only be used for thermo stable, moisture sensitive or moisture impermeable pharmaceutical and medicinal. These include products like; Dry powdered drugs, Suspensions of drug in non aqueous solvents, Oils, fats waxes, soft hard paraffin silicone, Oily injections, implants, ophthalmic ointments and ointment bases etc.
  • Gaseous sterilization is used for sterilizing thermo labile substances like; hormones, proteins, various heat sensitive drugs etc.
  • U.V light is perhaps the most lethal component in ordinary sunlight used in sanitation of garments or utensils.
  • Gamma-rays from Cobalt 60 are used to sterilize antibiotic, hormones, sutures, plastics and catheters etc.

Dry Heat Sterilizers

Hot air oven is one of the dry heat sterilizers. These sterilizers use dry heat for killing microorganism and are better than the steam sterilizers in the sense that the process does not corrode the machines. This is also used to sterilize liquids with low moisture content and also for treatment of medical powders. The process completely destructs all microorganisms and does not cause any environmental pollution or inconvenience to humans. Usually made up of stainless steel, the shape and position of heating elements in the chamber ensure uniform temperature distribution. The entire process includes drying, heating, sterilizing and cooling phase.

The benefit of dry heat includes good penetrability and non-corrosive nature which makes it applicable for sterilizing glass wares and metal surgical instruments. It is also used for sterilizing non-aqueous thermostable liquids and thermostable powders. Dry heat destroys bacterial endotoxins (or pyrogens) which are difficult to eliminate by other means and this property makes it applicable for sterilizing glass bottles which are to be filled aseptically.

Dry heat kills the organisms by destructive oxidation of essential cell constituents. Killing of most resistant spores by dry heat requires a temperature of about 160 degree C for 60 minutes.

Maintenance of Dry Heat Ovens

Maintenance of dry heat oven is an integral part of every dry heat sterilization procedure it can be achieved by

  • Keeping the oven clean at all times
  • Temperature gauge should be check on regular basis. This can be done by putting a thermometer in the oven and comparing the temperature reading with the one on the gauge.

Application of Dry Heat Sterilizers

  • Sterilizing laboratory instruments
  • Sterilizing ampoules
  • Sterilizing injection bottles
  • Sterilizing pharmaceutical vessels
  • Sterilizing medical instruments

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