What is ACH (Air Change Per Hour)?

While designing the ventilation systems, it is always taken into consideration that the usage purpose of the spaces and the people in the spaces will pollute the air. While calculations are made, the approximate value experienced per person in the space is taken. The usage purposes of the venues may change over time or the number of people may increase. The same conditions should be observed when choosing an air cleaner. The amount of fresh and clean air needed per person is determined by the authorities.

What is ACH (Air Change per Hour)?

Air change per hour (ACH or ACPH) is a measurement of air volume that is added to a room divided by the total volume of the room. Put simply, it measures how many times the air in the room is replaced. Higher ACH values mean better ventilation. The formula is as follows:

ACPH = Q / Vol

Whereby:

  • Q = Volumetric flow rate of air in cubic metres per hour (m³/h)
  • Vol = Space volume L × W × H in cubic metres (m³)

This table shows us the reference values of air volume by room usage according to DIN 1946.

If you’re not sure how to determine your room value or choose the correct air purifier, you can contact us directly.

Room

Minimum Outside Air
Stream per Person (m³/h)

Recommended Number of
Air Changes per Hour

Toilets

30

4 (private) 10 (public)

Showers

60

6 (private) 10 (public)

Offices

40-60

6

Restaurants

50

12

Canteens

30

12

Classrooms

30

5

Conference Facilities

30

8

Multi-purpose Halls

30

5

Gyms

30

5

Waiting Rooms

30

6

Hotel Rooms

4

Public Garages

5

Commercial Kitchens

25

Private Kitchens

20

Launderettes

18

Swimming Pools (private)

6-7

Workshops

10