Fresh Air Ventilation System Design: A Practical Overview

Updated August 31, 2026 — English wording and readability reviewed. Original publication date retained.

Planning a fresh air ventilation system starts with three questions: where should the air flow, how much outdoor air is needed, and how will the system operate? This overview introduces these design considerations and the information to prepare before equipment selection.

The occurrence of diseases such as haze, influenza and tuberculosis has caused China to pay great attention to indoor air quality. Central fresh air system is an inevitable choice for the development of building technology, building energy saving can not be separated from the fresh air ventilation system, people's health can not be separated from the fresh air ventilation system. As more and more families choose to install centralized fresh air system, centralized fresh air has long become a household name in existence.

Three Design Principles

1. Airflow Paths

Define the path of ventilation: fresh air from outdoors enters the room from bedrooms, living rooms, etc., and is then discharged from bathrooms, dining rooms, etc., where dirty air is easily generated.

2. Outdoor Airflow Requirements

Determine the minimum amount of fresh air in the housing - to meet the amount of fresh air people need for their daily life indoors.

3. Operating Schedule

Ensure the continuity of ventilation - 24 hours a day, 365 days a year according to the first and second principles of continuous ventilation.

Calculation method

A number of air changes method.

G=SxHxnxVe(80%-100%)

G - total air volume

S---Set use area

H --- height of the dwelling

n---the number of air changes

Ve --- effective volume

(Indoor use volume excluding fixed furniture, storage rooms, etc. is generally 80%-100%)

Table: Minimum number of air changes in residential building design

B. Minimum fresh air volume:

  G=V×n

  G - total air volume

  V - the minimum fresh air volume required per person (check table 3.0.6-1)

  n - the number of people in the residence

           Minimum fresh air volume required per person in main rooms of public buildings [m³/(h-people)

Area corresponds to the machine

Fresh air design principles

Notes:

1 The numerator of the listed values is the recommended flow rate, and the denominator is the maximum flow rate.

2 For systems with anechoic requirements, the flow rate in the duct should be in accordance with the provisions of 10.1.5 of this specification.

Air outlet selection

          Green is the recommended value for branch pipes, yellow is the recommended value for supervisors, and red is the alert value.