SOP for Cleaning of AHU (Air Handling Unit) Filter

Currently, there are several proven and successful methods, or combinations of methods, used throughout the world to clean AHU Filter. There is also a wide range and variety of air duct cleaning equipment and tools commercially available to cleaning contractors.

Depending on many different factors, any given method and equipment selection may allow for cleaning to an acceptable cleanliness level. This SOP provides AHU Filter Cleaning Services with basic principles behind several different methods of cleaning.

What is an AHU filter?
An air handler is usually a large metal box containing a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers. Air handlers usually connect to a ductwork ventilation system that distributes the conditioned air through the building and returns it to the AHU.

Which filter is used in AHU?
Prefilter is the first filter installed in the AHU to prevent dust particle particle to pass through air. It can also be called micro filter and is around 5micron.

What is the main function of AHU?
An Air Handling Unit is used to re-condition and circulate air as part of a heating, ventilating and air-conditioning system. The basic function of the AHU is take in outside air, re-condition it and supply it as fresh air to a building.

What is a HEPA filter used for?
HEPA stands for high-efficiency particulate air. A HEPA filter is a type of mechanical air filter; it works by forcing air through a fine mesh that traps harmful particles such as pollen, pet dander, dust mites, and tobacco smoke. HEPA filters in most air purifiers.

SOP for Cleaning of AHU (Air Handling Unit) Filter

To provide cleaning instruction of various types of filters in AHU as per safety and cGMP requirements.

Provide documented procedures for cleaning various types of filters in AHU as per safety and cGMP requirements.

Engineering - Technician
Engineering - Supervisor
Engineering - Manager 


Ensure prior to cleaning:
  • Ensure that area connected to the respective AHU is not in any use by its respective user department.
  • Intimate user department.
  • Stop the respective AHU. Switch off the AHU of which filter to be cleaned and display "UNDER MAINTENANCE LABEL". 

Cleaning Procedure for pre-filter and fine filter:
  • A person carrying out filter cleaning should wear the following:
  1. Clean appron and Caps
  2. Nose mask
  3. Eye goggles
  4. Rubber hand Gloves
  • Remove the filters to be cleaned from the AHU by unscrewing all its bolts and put into the polythene bags.
  • Number the filters with marker pen as per their original location so that they can be refixed on their same location.
  • Take all the filters to the filter cleaning room.
  • Wear rubber gloves and eye goggles.
  • Spray compressed air on the filter in the direction opposite to the airflow direction when the AHU is under working conditions. Continue this process as per the requirement of cleaning. Maintain air pressure in the range of 2 to 3 kg/cm2.
  • Ensure that filters are visually cleaned.
  • Then clean the filters with the help of tap water.
  • Then again spray compressed air on the filter in both directions. Continue this spray unless all the water is removed from the filter and the filter is thoroughly clean.
  • For drying the cleaned filter again open the compressed air valve and dry it again.
  • Also clean all the sections of AHU like the return air section, supply air section, fan–motor section, cooling coil section and all the sides of AHU with cotton dipped in potable water and final drying using dry cotton waste.
  • Refix all the filters as per their number on their original position.
  • Also, clean the filter cleaning room.
  • Maintain the cleaning record as per attachment-I

Frequency of Cleaning:
  • Weekly for Return Filter
  • Every 15 days for the AHU filter
  • Sampling booth riser after sampling completion of API material.
  • Dispensing booth riser after complete batch dispensing.

Master Copy: Quality Assurance Department
Controlled Copy: Engineering Department
Display Copy: Engineering Department

Revision History

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