When a lens is removed/replaced from a camera, it is possible for small dust particles to get in the imager chip enclosure.
These small dust particles can land on the imager chip surface or on the IRC (Infrared Cut) filter, where they will affect the image quality.
The small dust particles on the imager or filter, can be seen as small dark spots in the camera image.
You can remove these particles by removing the lens, and carefully blow the particles away with compressed air.
The IRC filter covers the imager chip surface, to this imager chip can not be reached directly (except for day-only cameras)
The air circulation in the imager enclosure will still blow the dust particles from the imager chip surface.
Do not touch the imager chip or IRC filter with any object.
The best way to use compressed air is a so called 'rocket blower'.
This is a hand operated rubber or silicone bellows with an air nozzle.
They can be found in camera shops.
You can also get compressed air in a can, known as a 'gas duster can'
This is not really just air, but some form of liquid gas in a can, with a nozzle.
Be careful when using gas dusters, if you tilt the can, liquid gas may shoot out.
This liquid can damage the camera parts, and leave residue on the imager or filter, making things worse.
Also, gas dusters do not allow much control over the force of the airflow.
Never use a 'garage style' compressor of the type that is used for inflating tires etc.
The air from it, contains small oil and water particles, that will be impossible to remove when they hit the imager and other camera parts.
Also, the pressure is way too high, and can damage camera parts.
Never open the camera housing to gain access to the imager.
If you are unable to remove the dust from the camera internals, please contact IQinVision support at firstname.lastname@example.org