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The origin of fogging can be traced to the 19th century when Joseph Lister aerosolised carbolic acid to improve antisepsis in operative practice.

Fumigation (fogging with formalin) is no longer used in the Western Literature and most of the International Infection Control Guidelines including CDC does not advocate fumigation practice as these developed nations have all the modern critical parameters required for OT in place with a well-equipped heat ventilation air conditioning (HVAC) system. HVAC system maintains indoor air temperature and humidity, control odours, remove contaminated air and minimise the risk of transmission of airborne micro-organisms. An HVAC system with modern AHU helps to maintain positive air pressure in OT, and maintain 15-20 air changes/hour. Use of HEPA filters (to remove particles of size of > 0.3 mm), laminar air flow and UV radiations further helps in maintaining asepsis and infection control.

In India, there are extreme situations in OT facilities, ranging from rooms with fans, window air conditioning, (OTs in DHs and CHCs) to the more sophisticated laminar airflow systems (medical colleges).

Most of OTs in DH and CHC do not have air handling unit (AHU) and other modern facilities with critical parameters. In hospitals that lack HVAC systems the quality of air in the OT cannot be guaranteed.

Although, no studies demonstrate that fogging actually reduces the incidence of hospital-acquired infections (HAI), it seems to be the only alternative for health facilities not having HVAC system. The method of fogging is recommended mainly to ensure uniform application of the disinfectant to all surfaces in the room. At the same time, the age old tradition of formalin fumigation is not recommended as it is difficult to perform, dangerous to use (especially the liquor ammonia), unreliable (as conditions required for bactericidal activity are difficult to maintain) and formalin itself is a known carcinogen.

Hence, disinfection of OTs is categorised into two categories:

  • Disinfection of OT with HVAC system
  • Disinfection of OT without HVAC system

Precautions to be taken

The following precautions should be taken while fogging:

  • Replace formalin with safer agents like "an aldehyde based product containing Glutaraldehyde and chemically bound formaldehyde as principal disinfecting agents" e.g. Bacillocid.
  • Advantages of these compounds are:
    • Has deep penetrating capability
    • Has no known resistant strains
    • Effective against Bacteria, Viruses, Mycobacteria, Amoeba, Fungi and spore forming organisms
  • After fogging do the air sampling and keep the records.

Disinfection of OT with HVAC system

Fogging is not required for an OT with a HEPA filtered positive pressure air supply system. However, the following should be ensured before deciding not to fogg such an OT:

  • The ventilation system design is appropriate and system performance is validated during installation and at least once a year. Records of validation should be available. All parameters in every validation testing should be within permissible limits
  • Maintenance of the ventilation system is done at least once a year. HEPA filters are changed at the time intervals recommended by the manufacturer or based on results of the validation tests. Maintenance of the AHU is done as a part of yearly maintenance. Records of maintenance filter replacement to be available
  • Weekly air count monitoring using settle plates/air sampler is done. Results are within acceptable limits and test reports are available
  • Surface cleaning protocols are implemented correctly with OT cleaning staff knowing clearly how they are supposed to perform the cleaning
  • Adequate time is given for OT cleaning.

General Steps

  1. Wear a gown, cap, mask and utility gloves
  2. Clean blood spills, remove waste, clean and disinfect items used in surgery
  3. Inspect all surfaces in the OT in detail for visible soiling/dust. Clean any soiling with an HLD
  4. Wipe and clean all equipment completely i.e. wipe the entire OT table, OT lights, trolleys, anaesthesia machine
  5. Lastly, clean and mop the floor twice (scrub by hand or a floor scrubber machine if possible) with a high-level disinfectant beginning at the end farthest from the door and moving towards it
  6. Cover all electronic equipment with plastic overs. The fogged liquid should not enter them
  7. Turn off the ventilation system
  8. Fog the OT with "an aldehyde based product containing Glutaraldehyde and chemically bound formaldehyde as principal disinfecting agents" e.g. Bacillocid* until a fog is seen in the air. Stop the fogging and exit from the OT with the machine
  9. Thereafter, the OT should be closed
  10. The OT should not be entered after it has been closed down for the day (except for emergency cases).

Disinfection of OT without HVAC system

  • After all cases are over, clean the OT as per the procedure for cleaning after all cases are over
  • Keep ventilation system off (in case it is working). Turn the AC off
  • Ensure all electronic equipment has been wiped and covered with a plastic cover (important to prevent the fogged liquid from going into the machines). No electronic equipment may be left uncovered
  • Prepare solution of "an aldehyde based product containing Glutaraldehyde and chemically bound formaldehyde as principal disinfecting agents" e.g. Bacillocid* solution in the fogger tank (quantity as per manufacturer recommendations). Place the fogger in one corner of the OT (preferably near a door so it can be taken out easily) on a trolley. Place a double folded towel under the machine (to prevent it from slipping off as it vibrates when running)
  • Direct the nozzle to the opposite corner of the room elevated at 45 degrees
  • Start the fogger and close the OT
  • Allow the fogger to run until a fog can be seen in the OT atmosphere. Check though the door window• Once a suspended fog is seen, wear a cap and mask, open the OT door, turn off the fogger and remove it to the outside
  • Keep the OT closed for at least one hour**. It may be used any time after thi.


  • Inspect the floor for wet patches after opening the OT. All surfaces should be dry. If water deposits are present keep the OT closed to allow them to dry naturally (turn AC on if available). Do not wipe the water with sterile mop
  • Check floor and working surfaces for excess stickiness (the foot slips or there are white streaks of deposit). This can be removed using soap and water. If excessive stickiness or deposits are observed, check the dilution of the cleaning and fogging solution and correct it if excess chemical was added during preparation. If the problem still persists, reduce the fogging time by 1-2 minutes and monitor.

Fogging of wards/rooms

Important: wards and rooms need not be fogged on a routine basis.

Fogging of wards and rooms should be done in the following situations:

  • After an isolation ward/room is emptied at the end of an outbreak
  • After an infected patient is discharged from a room (in absence of an outbreak)
  • When an outbreak of infection occurs in a ward.

The general steps for cleaning and fogging of a ward/room are as follows:

  • Wear cap, mask, gown and utility gloves. Arrange all cleaning material before beginning
  • Perform thorough cleaning as mentioned for terminal disinfection
  • First remove contaminated items, waste, linen, instruments to be cleaned
  • Change the gloves and begin cleaning from periphery to centre. Move from clean to unclean areas and top to down. The general order would be doors, walls, windows and wall mounted objects, floor-based furniture and patient care items, attached toilets and lastly, floor
  • After cleaning is over, close the windows and doors and fog the area with "an aldehyde based product containing Glutaraldehyde and chemically bound formaldehyde as principal disinfecting agents" e.g. Bacillocid* until a good fog is seen in the air
  • Stop fogging, remove the fogger machine and keep the area closed for at least one hour**. It can be used after this

Source: Guidelines For Implementation Of "KAYAKALP" Initiative

Last Modified : 2/12/2020

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