The most important facts about indoor guide values

In the course of the coronavirus pandemic, the issue of indoor air quality has increasingly become the focus of public attention. This is mainly due to the fact that airborne aerosols are one of the main carriers of viruses such as COVID-19. However, aerosols also pose other health risks, for example when carcinogenic chemical compounds attach themselves to them. Regular ventilation and compliance with scientifically based guideline values are therefore of great importance. In this article, you will learn about the most important guideline values and ways to implement them.


About the Committee for Indoor Guide Values

Indoor air is the central entry pathway for organic and inorganic compounds. For this reason, the Committee for Indoor Air Quality Guidelines (AIR) regularly determines health-related guideline values and hygienic guide values for indoor air quality in public and private buildings. On this basis, concentrations of chemicals in indoor air can be systematically evaluated.

The committee is made up of experts from the federal and state governments who are appointed on the basis of a mandate from the Working Group of the Supreme State Health Authorities. In addition, other experts may be appointed to work on the AIR as required - for example from the Federal Institute for Risk Assessment, the Indoor Air Hygiene Commission (IRK) of the UBA, the German Institute for Building Technology (DIBt) and the Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA).

The committee received its mandate from the health ministers of the federal states in 1994. Since then, its main objective has been to define uniform national standards for the health assessment of pollutants in indoor air. The establishment of the committee was a response to the very inconsistent assessments of the federal states at the time and set clear assessment standards in motion. Initially known as the Ad-hoc-AG Indoor Air, the committee now works on the ongoing task of improving air quality as the Committee for Indoor Guide Values.


What are interior spaces?

According to the definition of the German Advisory Council on the Environment , indoor spaces are:

  • Private apartments with living rooms, bedrooms, craft, sports and cellar rooms, kitchens and bathrooms
  • Workrooms in buildings that are not subject to the scope of the Hazardous Substances Ordinance (GefStoffV) with regard to hazardous substances, such as offices
  • Interiors in public buildings (hospitals, schools, daycare centers, sports halls, libraries, restaurants, theaters, cinemas and other public event spaces)
  • Interiors of motor vehicles and public transportation


These guide values for indoor air exist

In order to assess the quality of indoor air in public and private buildings, the Committee for Indoor Guide Values uses a precautionary and a hazard guide value as well as a hygienic and a risk-related guide value.

Reference value I (precautionary reference value):
The precautionary guideline value specifies the concentration of a pollutant in indoor air which, according to current research, does not pose a risk of health damage even after a lifetime of exposure. If guideline value I is exceeded, action should be taken as a precautionary measure. At the same time, measures should be taken to reduce the concentration of pollutants. In this way, guide value I can be used as a target for planned remediation.

As a counterpart to the hazard guideline values, the assessment standard emphasizes that environmental health protection always involves long-term precautionary measures far below hazard thresholds. An overview of the guide values can be found on the website of the Federal Environment Agency.

Guideline value II (hazard guideline value):
The second parameter is an effect-related value. It refers to the current toxicological and epidemiological knowledge on the effect threshold of pollutants. If it is reached or exceeded, immediate action must be taken - for example by closing the premises. Otherwise, there is a sufficient probability of damage to health.

The introduction of hazard guideline values goes back to the central demand at the beginning of the committee's work in the 1990s to establish a link to building law. The building regulations of the federal states stated, among other things: "Building installations must be designed in such a way that hazards due to chemical, physical or biological influences do not arise." The need to take this aspect into account with the guideline values was correspondingly central.

You can find an overview of the guide values on the website of the Federal Environment Agency.

Hygienic conductance:
The hygienic guide value specifies threshold values for the concentration of carbon dioxide, carbon monoxide and particulate matter. Surveys have shown that high concentrations of these substances in indoor air increase the likelihood of health complaints. However, no purely toxicologically based guideline value can yet be derived from the scientific findings to date. The following guide values have therefore been introduced for carbon dioxide, carbon monoxide and particulate matter.

Risk-related guide values:
The risk-based guide values provide information on the health risk of carcinogenic substances in indoor air. They are based on indoor air measurement data on the occurrence of tested substances and toxicological or epidemiological data on the exposure-risk relationship. Substances in this category include benzenes, for example. You can find an overview of the guide values on the website of the Federal Environment Agency.

In the past 10 years alone, the AIR has derived guideline and reference values for more than 45 pollutants and pollutant groups, which have been published together with detailed explanatory papers in the official section of the Federal Health Gazette.


Options for implementing the interior guide values

The basic prerequisite for implementing the indoor guide values is constant air circulation within the building. However, this is not easy to achieve. As modern buildings are being built ever more tightly in the interests of maximum energy efficiency, less and less air can be exchanged through small gaps and cracks. It is therefore necessary to open the window regularly.

However, this is problematic in offices, for example, if the windows cannot be opened permanently due to bad weather or traffic noise. Another problem in private rooms is that most people are not at home during the day, which is why ventilation is only possible in the morning and evening.

For these reasons, a decentralized ventilation system is the best choice in many cases. It draws in stale air from utility rooms such as kitchens and bathrooms and feeds fresh air from outside into the interior of the building. This ensures a constant flow of uncontaminated air. With technologies such as heat exchangers, the heat energy from the exhaust air can even be transferred to the fresh air.

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