PHYSICAL METHODS OF STERILIZATION

Physical methods of sterilization involve the application of heat, radiation, or filtration to eliminate or destroy microorganisms and their spores.

Here are some common physical methods of sterilization:

1. Autoclaving:
   • Method: Autoclaving utilizes steam under pressure.
   • Process: The items to be sterilized are exposed to high-pressure saturated steam at temperatures typically ranging from 121 to 134 degrees Celsius (250 to 273 degrees Fahrenheit).
   • Application: Autoclaving is effective for sterilizing surgical instruments, laboratory glassware, and other heat-resistant materials.
2. Dry Heat Sterilization:
   • Method: Dry heat sterilization involves hot air.
   • Process: Items are exposed to high temperatures (e.g., 160 to 180 degrees Celsius) for an extended period.
   • Application: Dry heat is suitable for items that may be damaged by moisture, such as powders, oils, and certain glassware.
3. Incineration:
   • Method: Incineration involves burning materials.
   • Process: The items are exposed to high temperatures until they are completely burned.
   • Application: Incineration is often used for the disposal of contaminated waste, particularly in laboratories.
4. Pasteurization:
   • Method: Pasteurization uses heat.
   • Process: This method involves heating liquids or food products to a specific temperature for a predetermined time to kill or reduce the number of pathogenic microorganisms.
   • Application: Commonly used in the food and beverage industry for items like milk and juices.
5. Radiation Sterilization:
   • Method: Radiation includes gamma radiation and electron beams.
   • Process: Items are exposed to ionizing radiation, disrupting the DNA of microorganisms.
   • Application: Gamma radiation is used for sterilizing medical devices, pharmaceuticals, and certain disposable items.
6. Filtration:
   • Method: Filtration uses porous materials.
   • Process: Liquids or gases are passed through filters with pore sizes small enough to trap microorganisms.
   • Application: Filtration is common for sterilizing liquids, especially in pharmaceutical and biotechnology industries.

PHYSICAL METHODS OF STERILIZATION

Heat kills all types of bacteria. Boiling is the most commonly used method in day-to-day working

Heat is the safest and most useful agent for sterilization in hospitals. Methods of applying heat for sterilization are exposure to steam under pressure, boiling, etc

Boiling (Moist heating): boiling an instrument/article immersed fully in boiling water (100 degree Celcius) for 10 minutes will kill most of the pathogenic organisms

General Instructions

• The articles should be clean
• The articles should be fully immersed in water
• Close the sterilizer lid tightly
• Note the time after the water has started to boil
• Boil it for 7 to 10 minutes
• Remove the articles with chattel forceps

Precautions

• Do not pick articles in between, when the boiling is in process
• Do not boil sharp instruments such as scissors, knives, needles, etc. because boiling blunt them

Advantages

• Boiling can be used in the home environment and other situation
• It is one of the economic ways of sterilizing articles

Disadvantages

• Some bacteria and viruses and all spores are resistant to boiling
• Boiling method cannot be used for the articles which are destroyed by moisture and heat