The fresh air system and central air conditioning are both common air handling systems in modern buildings. While they are both related to indoor air, their functions, principles, and purposes are completely different. Below is a detailed comparison:

1. Different Functional Focus

The primary function of a fresh air system is to introduce fresh outdoor air and expel stale indoor air, thereby improving air quality.
The main function of a central air conditioning system is to regulate indoor temperature, providing cooling or heating to enhance comfort.

2. Different Working Principles

A fresh air system uses supply and exhaust fans to bring in outdoor air and remove indoor air. Some systems also include heat recovery units to reduce energy loss.
A central air conditioning system uses compressors and fan coil units to cool or heat the indoor air in a closed-loop circulation without exchanging air with the outdoors.

3. Different Air Sources

Fresh air systems process outdoor air, which is filtered before being delivered indoors.
Central air conditioning systems process indoor air, recirculating it without introducing fresh air.

4. Impact on Health and Energy Efficiency

Fresh air systems help increase oxygen levels, reduce bacteria and odors, and are better for long-term health, especially in enclosed spaces.
Central air conditioning, if used alone for extended periods, can cause stuffy air and promote bacterial growth due to lack of ventilation, which may negatively affect health.

5. Can They Replace Each Other?

Fresh air systems cannot regulate temperature, so they cannot replace air conditioning.
Central air conditioning systems do not provide fresh air, so they cannot replace fresh air systems. Their functions are complementary and not interchangeable.

Conclusion

In simple terms: Central air conditioning adjusts temperature; fresh air systems handle ventilation. Each plays a different but essential role. To achieve both comfort and healthy indoor air, it is recommended to use both systems together.