scope:

Introduction

An adequate air change is of fundamental importance for indoor air quality. Proper ventilation of all buildings is necessary for the health and comfort of the occupants, but also to protect against damage, for instance due to excessive atmospheric humidity. However, the present-day fitting of tightly-sealing windows, for example, to residential and office buildings can, in addition to the desired energy savings and noise reduction, lead to insufficient ventilation, which leads to an increase in concentration of substances emitted indoors [1]. Manual ventilation by the occupants or the use of mechanical ventilation systems is thus required, especially during the heating period. However, excessive ventilation can lead to discomfort and increased energy consumption during the heating period.

In order to be able to make meaningful statements on ventilation conditions indoors, it is necessary to determine the air change rate n. With knowledge of the air change rates, it is possible to test whether health and structural ventilation objectives are complied with.

In this guideline, methods are described for determining the indoor air change rate based on measuring the concentration of tracer gases. Important boundary conditions which are to be maintained during the measurement of air change rate and interpretation of the results are considered in the examples.

In principle, the methods described can be applied to all indoor areas where complete mixing of the air can be shown to be assumed or where via fans or vortexing during the measurement complete mixing can be produced artificially.

Exceptions include rooms where there is no complete mixing and, for the duration of the measurement, cannot be artificially produced either. These include, especially, rooms having deliberate cross-ventilation, short-circuit flow, source ventilation (where this cannot be artificially changed into mixing ventilation during the measurement) and rooms having intensive local extractors (e.g. welding shops, swimming pools or metal foundries).