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Chapter: 11th 12th std standard Class Nursing Health Care Hospital Hygiene Higher secondary school College Notes

Disinfection and methods

Disinfection is the process of killing the pathogenic or disease producing microorganism but not usually bacterial spores.

Disinfection and methods:


Disinfection is the process of killing the pathogenic or disease producing microorganism but not usually bacterial spores.


Disinfectant is germicide an agent which kills pathogenic or disease producing microorganisms but not usually bacterial spores. Eg . phenol and Lysol.

A deodorant is an agent, which suppresses bad odours. Eg. Lime , bleaching powder


Detergent is a surface cleansing agent, which acts by lowering surface tension. Eg soap.


Antiseptic is an agent which prevents the growth of microorganisms. Eg alcohol.


Sterilization is  a  destruction of microorganisms and their spores.


Types of Disinfection:


1.     Concurrent disinfection: This is disinfection of infectious material ( eg stools, urine contaminated linen) through out the course of an illness . This procedure checks or prevents the dissemination or further spread of the disease agent.


2.     Terminal disinfection: This is disinfection that is undertaken at the termination of an illness. ( eg. After recovery or death of the patient).


3.     Prohylactic disinfection: Boiling of water, pasteurisation of milk, washing hands with soap and water are examples.

Sterilisation :


 It  is one of the methods of disinfections which is stated above.


Methods of disinfection:


1.     Natural: Sunlight and air


2.     Physical: Dry heat , moist heat and radiation


3.     Chemical: Liquids, solids and gases.


Preparing articles for disinfection (sterilization):


A convenient method often used is to prepare sets of the instrument, swabs, sponges, dressings, towels and the surfaces needed for each type of operation or sterile procedures.

These sets are packed into drums, bundles or on trays, labeled and kept ready for sterilising.

The articles should be carefully arranged so that those needed first are on top.

They must be loosely packed for steam to penetrate.

Drums or bins must have the perforations opened.

Bundles should have a double wrapper of close-woven cloth, or of paper.




Swabs and sponges are usually made of several thickness of surgical gauze. Raw edges must be folded to the desired size to prepare gauze. Sponges used for abdominal surgery need to be large, stitched around the edge and a piece of tape sewed to one corner. When an artery forceps is clipped into the end of the tape, there is no risk of the sponge being left inside the abdomen.


B.  Packing gauze:


It is made in various sizes. Use gauze four times the width of the desired packing. Fold the edges so that they meet in the middle and again fold down the center, and roll.


C. Cotton balls:


It is prepared in various ways. Cotton balls of various sizes are prepared by rolling between the palms. Some may be needed for intestinal surgery, and for this the cotton ball must be covered with gauze and tied. This type of ball is grasped with a long handed forceps.


D. Instruments:


After use, surgical instruments should be washed first in cold water then in warm water with a detergent. Use a brush to clean well especially between the teeth of artery forceps and clamps. To be properly sterilized, there should be no dried blood or discharge. Rinse in clean water, then boil for 5 minutes and dry well.


Sharp instruments, knives and needles should be dealt with separately, taking care to avoid cuts and puncture wounds.


E.  Glass syringes and metal needles:


After use, draw up some water into the glass syringe and push enough through each metal needle to make sure they are not blocked. Infected glass syringes (used for withdrawing blood or pus) should be washed immediately in cold disinfectant solution.

Next wash the syringes and needles in warm soapy water, using a bottle brush for the barrel. Rinse in clean water. Take care not to get barrels and plungers mixed, but keep them always paired together.


Needles should be examined carefully for sharpness. Take care not to prick your finger as infection may be transmitted in this way.


F. Rubber tubing


After use tubes should be cleaned with cold water, then with hot soapy water and then rinsed. The inside must be thoroughly cleaned. Then it is boiled, and hung over. Rubber catheters should be cleaned by running cold water through from both ends. Wash and rinse in cold water, then dry, with a towel or by hanging up. Autoclave the catheters before use.


Disinfecting methods (sterilisation- physical ):


Dry heat:


Sterilizing of glassware including syringes is often done in a hot air oven at 1600c for one hour.


Spores as well as organisms are killed. Rubber articles will not withstand this heat.


This method is not efficient where heat has to penetrate as in dressings, towels and gowns.


Moist heat : Autoclaving (Steam under pressure):


1.     This is a reliable method and may be used for most articles.


2.     The autoclave is a chamber with an outer jacket and a lid or door, which can be firmly clamped.


3.     Steam, is generated by heating water in a boiler or in the outer jacket.


4.     Air is evacuated from the chamber by displacement.


5.     Then the steam is allowed to build up pressure, usually 15 to 20 lbs per square inches, and is kept at that pressure for 15 to 30 minutes.


6.     Then the heat is turned off and the contents of the autoclave allowed to dry out.


7.     They should be quite dry when removed from the autoclave.


Points to remember:


1.     All articles should be clean and dry before packing. Any organic matter such as blood or pus prevents penetration of steam.


2.     The holder in the drums must be open when placing into the autoclave and closed immediately on taking them out.


3.     Bundles should be neither be too large nor be too tightly packed. Steam should be able to penetrate to the center.


4.     Rubber gloves cannot withstand high temperature and long sterilising. Autoclave them separately at 15 lbs pressure for 15 minutes.


5.     To autoclave bottles of fluid, loosen the screw cops, evacuate the steam slowly.




       I.            This  method  is  suitable  for enamel,  metal,  glass and rubber ware.

    II.            Bowl sterilizers are used for larger articles and instrument sterilizers for smaller articles.


Points to remember:


1.     See that the articles are quiet clean and completely immersed in clean water.


2.     When the water boils, start timing. If more articles are added, the sterilizing time must begin again.


3.     Boil for 5 minutes.


4.     Boiling will not kill spores


5.     Remove articles with sterile cheatle or other lifting forceps, and place them on a sterile surface.


Chemical disinfection:


This method is used for sterilising delicate instruments such as eye instruments.

Points to remember:


1.     The articles must be clean and free from pus, blood or oil.


2.     They must be completely immersed in the disinfectant.


3.     The disinfectant should be of certain strength, and the articles must be in contact with it for a specific period.


4.     After sterilization, articles must be well rinsed in sterile water before use.


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11th 12th std standard Class Nursing Health Care Hospital Hygiene Higher secondary school College Notes : Disinfection and methods |

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