What is the most popular filter used in air conditioning in the operation room? and where is it placed?

HEPA filters will be used and it will be installed in the terminal after AHU fan outlet.

HEPA filter normally placed at the end of the terminal unit to ensure clean air reaches the room.
If it is placed at the outlet of the fan the air may get contaminated with the duct till it reaches the operating room.

HEPA filter, either downstream of the cooling/heating coil or at the terminal.
Carrier has introduced UV Light Sterilization technology for cleaner air.

HEPA filters, It Should be installed after AHU fan outlet.

High efficiency Particulate air filter (HEPA). It provides 99.97% filteration

HEPA filter ( High-efficiency particulate arrestance)

HEPA filter and fix the supply air duct