Calculating the appropriate air volume is crucial for maintaining optimal indoor air quality. Proper ventilation ensures the removal of pollutants and replenishes the space with fresh air, contributing to a healthy and comfortable environment. In this blog post, we will explore the formulas and guidelines for determining the required air volume based on air change rates and the number of occupants in a building.

Calculating Air Volume:

To calculate the air volume needed for a particular building, we can utilise an air change rate relevant to the space. The air change rate refers to the number of times the entire volume of air in a room is replaced within a given time period. Let’s refer to the table below for guidance:

Building TypeAir Change Rate (per hour)
General Building4 – 8
Conference Rooms6 – 12
Restaurants10 – 20
Table of Building Types & Air Change Rate

However, it’s essential to crosscheck the calculated air volume against the number of occupants to ensure compliance with the minimum fresh air requirements. The minimum fresh air requirement typically ranges from 8 L/s (litres per second) per person, doubling if smoking is permitted, to approximately 18-20 L/s for conference rooms and restaurants. As a general rule, an average figure of 12 L/s per person can be used.

To calculate the air volume, follow these steps:

  1. Determine the number of occupants in the building.
  2. Multiply the number of occupants by the fresh air requirement per person (e.g., 12 L/s).
  3. This result gives you the total fresh air requirement in litres per second (L/s).
  4. Convert the fresh air requirement from litres per second (L/s) to cubic meters per hour (m³/h) by multiplying by 3.6.

For example: If a building has 50 occupants, the total fresh air requirement would be: 50 occupants × 12 L/s = 600 L/s

Converting to cubic meters per hour: 600 L/s × 3.6 = 2160 m³/h


Calculating the required air volume is crucial for maintaining optimal indoor air quality. By considering the air change rate relevant to the building type and the number of occupants, HVAC professionals can ensure adequate ventilation and comply with minimum fresh air requirements. Proper ventilation plays a significant role in removing pollutants, controlling humidity, and creating a healthy and comfortable indoor environment. By following the formulas and guidelines outlined in this blog post, you can enhance the air quality in various spaces, promoting the well-being of occupants and contributing to a pleasant atmosphere.