"Fresh air system" and "fresh air machine" are two common concepts in the field of air purification and ventilation. Although both are related to ventilation, 

they have significant differences in design, function and application scenarios.

‌1. Definition and composition‌

‌Fresh air system‌ (whole-house fresh air system)

It is a complete ventilation system, usually composed of a host + pipes + vents + control system, which delivers fresh air to all areas of the house through pipes 

and discharges indoor dirty air.

It includes energy recovery (such as ERV/HRV heat exchange), multiple filtration (PM2.5, pollen, etc.), temperature and humidity adjustment and other functions.

It is suitable for overall ventilation of the whole house, and the pipeline layout needs to be planned in advance during the decoration stage.

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Fresh air machine‌ (single fresh air equipment)

It is an independently operated ventilation equipment that does not require complex pipes. Common forms include wall-mounted, cabinet-type, window-type, etc.

The function is relatively simplified, mainly realizing local space ventilation (such as a single room) through one-way or two-way airflow.

It can be installed later without destroying the wall or decoration structure.

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2. Function comparison‌

‌Air circulation efficiency‌:

The fresh air system realizes air circulation throughout the house through pipes, with uniform ventilation and few dead corners.

Fresh air fans rely on natural diffusion, and the ventilation range is limited, which is easy to form airflow dead corners.

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Energy recovery‌:

High-end fresh air systems are usually equipped with ERV/HRV heat exchange cores to reduce energy loss.

Most fresh air fans do not have heat exchange functions (except for a few high-end models), and directly introduce outdoor air, which may cause indoor temperature 

and humidity fluctuations.

‌Filtering capacity‌:

Fresh air systems mostly use multi-stage composite filters (primary + HEPA + activated carbon) to purify particulate matter, formaldehyde, etc.

Fresh air fans have fewer filtration levels (some models only have primary filters), and the purification effect is weak.

‌3. Applicable people and scenarios‌

‌Choose a fresh air system‌:

New house decoration, pursuing whole-house air quality and energy saving.

Sensitive to PM2.5 and allergens, deep filtration is required.

The area is cold in winter or hot in summer, and energy recovery is required to reduce energy consumption.

‌Choose a fresh air fan‌:

The house has been decorated and ducts cannot be installed.

The budget is limited, and only local space ventilation is required (such as bedrooms and study rooms).

Renting a house or temporarily improving air quality needs.