Information on limit values of gases, particles and pollutants in the air we breathe.

The Federal Environment Agency specifies a daily limit value of 50 μg/m³ for particulates particles PM10, which may only be exceeded on 35 days a year. In general, a maximum annual mean value of 40 μg/m³ applies. For the smaller particles PM2.5, there are only non-binding target values of 25 μg/m³ set by the EU and WHO. For even smaller particles - although infinitely more dangerous - there are currently no limit values.

The EU specifies a limit value of 200 µg/m³ as the maximum limit for the mean value of an hour. This limit may not be exceeded more than 18 times per year. If a value of 400 μg/m³ is exceeded within three hours, immediate action must be taken. The Federal Environment Agency specifies guideline values for indoor areas - 80 µg/m³ as an hourly average and 40 µg/m³ as an annual average. The short-term alarm value is 250 µg/m³.

The occupational exposure limit (OEL) of NO₂ is set at 950 µg/m³ with numerous exceptions. However, this high value applies in particular to workers who are exposed to increased nitrogen dioxide pollution at their workplace, i.e. who do not work in offices. The Federal Environment Agency recommends - also indoors - setting the maximum weekly mean value at 40 µg/m³.

The Federal Environment Agency recommends ventilating as soon as a value of 1,000 ppm carbon dioxide is exceeded. The maximum workplace concentration (MAK value) specifies a limit of 5,000 ppm. DIN-1946-2, which is no longer valid, stipulated a limit of 1,500 ppm. In children's rooms, bedrooms and fully occupied classrooms or meeting rooms, values of over 5,000 ppm can be measured quickly.

The Federal Environment Agency specifies a 24-hour average value of 4 mg/m³ for carbon monoxide. The maximum workplace concentration (MAK value) of carbon monoxide is given as 35 mg/m³ - the MAK values do not apply to pregnant women or people with pre-existing conditions. The WHO recommends that values above 25 mg/m³ should not be inhaled for more than one hour, and values up to 85 mg/m³ for a maximum of 15 minutes. The Federal Environment Agency is somewhat less strict here with 100 mg/m³.

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There are no legal limits for oxygen in Germany. DGUV Rule 113-004 of the German Social Accident Insurance for Occupational Safety specifies a value of 17 % oxygen. The amount of oxygen still present in exhaled air is 16 %.

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The Federal Environment Agency sets a maximum 8-hour value for ozone of 120 µg/m³ (60 ppb), which may be exceeded on a maximum of 25 days per calendar year. However, the UBA recommends that this value should not be exceeded at all. From a value of 180 µg/m³, the population must be informed, and from 240 µg/m³, an ozone alarm must be triggered.

There is currently no occupational exposure limit value (OEL, formerly MAK). Since no OEL has yet been established for ozone, the previous TLV of 200 µg/m³ is considered a non-binding guideline. For offices, the limit values of the Federal Environment Agency apply.

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The EU has set the following sulphur dioxide limits: The one-hour limit value is 350 µg/m³, the daily limit value is 125 µg/m³. Furthermore, an alarm threshold of 500 µg/m³ applies to sulphur dioxide. A concentration of 2.5 mg/m³ (1,000 µg/m³ or 1 ppm) is set as the occupational exposure limit value (OEL) for sulphur dioxide.

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The German Radiation Protection Act sets the reference value for radon concentrations. The limit value of 300 becquerels per cubic metre (Bq/m³) applies indoors - this means 300 decays per second per cubic metre of air. Upon request, the landlord or employer must be able to prove these values. The German Radiation Protection Commission (SSK) recommends ventilating from 250 Bq/m³ and permanently reducing the value below 100 Bq/m³ - as does the World Health Organisation WHO. At more than 1,000 Bq/m³, remediation should take place to protect against radon.

There are no fixed limit values for absolute humidity. Recommended values are between 6.9 and 10.4 g/m³, which are the limits of too dry and too humid air at room temperature. At lower or higher temperatures, however, these values can quickly become uncomfortable.

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There are no legally specified limit values for relative humidity. Values between 40 and 60% are recommended. This is the limit for room temperature between air that is too dry (dry throat and eyes) and air that is too humid (mould!).

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Since methane is non-toxic to humans, no limit values have been set for this gas. However, the high flammability of methane poses a significant risk. The lower explosion limit (LEL) is considered to be a methane content of 29 g/m³ - which corresponds to 4.4 vol.-% (volume percent). Above this level, flame propagation in the gas mixture occurs completely independently in the event of ignition (explosion).

Methane is also known as a dangerous climate gas and thus a contributor to man-made climate change. In recent years, the methane content in the atmosphere has been rising rapidly.

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The Federal Institute for Risk Assessment (BfR) sets a maximum formaldehyde concentration of 0.1 ppm (parts per million). The World Health Organisation (WHO) recommends a maximum of 0.08 ppm as the formaldehyde limit value. In the workplace, the MAK value of 0.3 ppm applies.

There are no relevant limit values for air pressure in normal environments. High deviations from the normal pressure of 1 hPa can also occur at workplaces. Exemptions are required below 0.73 and above 3.6 hPa. Even at deviations of 0.1 hPa from normal air pressure, significant health restrictions are to be expected and certain groups of workers may no longer be employed.

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In the official TA Lärm (Technical Instructions on Noise Protection), maximum limits are set for indoor areas (25 dB at night, 35 dB during the day). Outdoors, different limits apply to different areas - in pure residential areas, for example, 50 dB during the day and 35 dB at night. The WHO has made a number of recommendations for specific noise sources and areas. In the immediate vicinity of wind turbines, the WHO recommends a maximum noise level of 45 dB, traffic noise should be below 53 dB during the day and 45 dB at night - always measured outside. The Noise Vibration Occupational Health and Safety Ordinance (LärmVibrationsArbSchV) applies to protection against the effects of noise at the workplace. It specifies various limit values depending on the type of activity, duration and specific location of noise exposure. For example, there are no special limit values for offices.

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In the official TA Lärm (Technical Instructions on Noise Protection), maximum limits are set for indoor areas (25 dB at night, 35 dB during the day). Outdoors, different limits apply to different areas - in pure residential areas, for example, 50 dB during the day and 35 dB at night. The WHO has made a number of recommendations for specific noise sources and areas. In the immediate vicinity of wind turbines, the WHO recommends a maximum noise level of 45 dB, traffic noise should be below 53 dB during the day and 45 dB at night - always measured outside. The Noise Vibration Occupational Health and Safety Ordinance (LärmVibrationsArbSchV) applies to protection against the effects of noise at the workplace. It specifies various limit values depending on the type of activity, duration and specific location of noise exposure. For example, there are no special limit values for offices.

The Federal Environment Agency makes recommendations for room air temperatures depending on use (e.g. living rooms 21 to 23 °C, children's rooms and bathrooms 23 °C, bedrooms 16 to 18 °C). For offices, a room temperature between 21 and 22 °C is recommended. According to the Workplace Directive (ASR), the maximum temperature in workrooms must not exceed 26 °C, otherwise the employer is obliged to take measures.

The Federal Environment Agency gives recommendations for the occurrence of Volatile Organic Compounds (VOCs) ranging from hygienically harmless (below 1 mg/m³ - below 150 ppb) to hygienically conspicuous (between 1 and 3 mg/m³ - 150 to 1300 ppb) and hygienically questionable (between 3 and 10 mg/m³ - 1300 to 4000 ppb) to hygienically unacceptable (above 10 mg/m³ - above 1500 to 4000 ppb). Many legally relevant sources mention mg/m³ as the unit. However, what is measured is a mixture of many substances with different molecular masses (also referred to as TVOC), whose volume fraction in the air is expressed in ppb (parts per billion) or ppm (parts per million). In Germany, legal limits for VOCs have so far only been set for workplaces with particularly high levels of production-related pollution.

As the gas has no direct effect on human health, no limit values have been set.