Air changes per hour in different spaces
The air change rate (ACH) indicates how many times the air in a space is completely replaced per hour. This is a crucial factor when designing or assessing an efficient ventilation system. Depending on the function of the space—such as an office, workshop, bathroom, or storage area—different guidelines apply for the recommended air change rate.
In this article, we explain what ACH means, which factors influence it, and provide an overview of recommended values for various applications.
Air changes per hour by room type: explanation and guidelines
Proper ventilation is essential for a healthy and comfortable indoor climate. A key concept in ventilation design is the air change rate: the number of times per hour the total volume of air in a room is renewed. Depending on the type of room—offices, restrooms, classrooms, or storage spaces—different recommended ACH values apply.
Spaces with high occupancy or processes that release pollutants naturally require a higher ventilation rate than low-activity storage areas. Factors like humidity, heat generation, and odors also play a role.
The table below provides an overview of recommended air changes per hour by room type. These values are based on widely used guidelines in the ventilation industry and serve as a strong starting point when designing or evaluating a ventilation system.
Note: The ACH value is only one part of a proper ventilation strategy. Airflow direction, exhaust points, and additional requirements (such as noise levels or ATEX compliance) can also be important.
| Application area | Air changes per hour (ACH) | Application area | Air changes per hour (ACH) |
|---|---|---|---|
| Potato storage | 30 - 40 | Machine rooms | 15 - 30 |
| Battery rooms | 10 - 15 | Assembly halls | 5 - 8 |
| (Traffic) tunnels | 40 | Press rooms | 10 - 15 |
| Bathrooms | 10 – 15 | Restaurants | 5 - 8 |
| Bakeries | 30 – 40 | Schools | 5 - 8 |
| Canning factories | 10 - 15 | Sports halls | 1 - 3 |
| Libraries | 5 - 8 | Ironing rooms | 10 - 15 |
| Flower bulb storage | 40 | Telephone exchanges | 7 - 10 |
| Pubs / Cafés | 10 - 15 | Textile factories | 15 - 30 |
| Showers | 10 – 15 | Theaters | 5 - 8 |
| Fruit storage | 40 | Toilets | 7 - 10 |
| Large garages | 5 - 8 | Meeting rooms | 5 - 10 |
| Small garages | 10 - 15 | Paint and repair shops | 20 - 50 |
| Changing rooms | 3 - 7 | Drying rooms | 5 - 10 |
| Foundries | 15 - 30 | Waiting rooms | 5 - 8 |
| Cutting factory | 100 | Department stores | 4 - 8 |
| Canteens | 5 - 8 | Laundries | 15 - 30 |
| Offices | 5 - 8 | Workshops | 5 - 8 |
| Churches | 1 - 2 | Shops | 5 - 8 |
| Restaurant kitchens | 15 - 20 | Living rooms | 3 - 5 |
| Dressing rooms | 5 - 8 | Hospital rooms & sour cabinets | 2 - 3 |
| Laboratories | 5 - 8 | Swimming pools | 1 - 5 |
| Light printing shops | 10 - 15 |
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Frequently asked questions about air change rates (ACH)
What is an air change rate (ACH)?
The air change rate indicates how many times the air in a space is completely replaced per hour. For example, an ACH of 5 means the entire volume of air in a room is renewed five times per hour.
How do I calculate the required airflow based on ACH?
The formula is simple:
airflow (m³/h) = room volume (m³) × desired ACH
This tells you how much air needs to be supplied or extracted per hour.
Is a higher ACH always better?
Not necessarily. A ventilation rate that is too high can lead to drafts, energy loss, and unnecessary installation costs. It’s essential to strike the right balance for comfort, health, and efficiency.
Where can I get advice on the right ACH for my application?
We’re happy to help. Contact us for tailored advice on your specific space or application. Together, we’ll find the best solution.
