--- title: "UBA CO₂ Limit Values | Aethair" description: "Indoor CO₂ Guideline (German UBA / Pettenkofer scale) limit values for Carbon Dioxide: every value and averaging period, who the standard applies to, and…" url: https://aethair.io/standards/uba_indoor_co2/ --- Compliance · Umweltbundesamt (DE) # Indoor CO₂ Guideline (German UBA / Pettenkofer scale) Indoor air: ventilation adequacy guidance Indoor carbon dioxide is not usually a direct toxic hazard at the concentrations found in occupied rooms; instead it is the classic **proxy for ventilation adequacy**. People exhale CO₂ continuously, so when it accumulates it signals that fresh air is not being supplied fast enough to dilute the other products of occupancy: odors, bioeffluents, and airborne pathogens. The reference point dates back to the 19th-century hygienist Max von Pettenkofer, who proposed a widely quoted indoor value of around **1000 ppm** as the threshold of acceptable air. The German Federal Environment Agency (Umweltbundesamt, UBA) formalized this into a banded guideline that classes indoor CO₂ as hygienically acceptable, elevated, or unacceptable. [Schedule a call](https://calendly.com/d/ctdd-mkr-v9v/aethair-demo-website) [Configure UBA CO₂ Monitoring](https://aethair.io/build/?params=co2) At a glance **Umweltbundesamt (DE)** Indoor air: ventilation adequacy guidance 1 parameter · 2 limit values [Carbon Dioxide (CO₂)](https://aethair.io/parameters/co2/) 1 device measures them all - **Aethair IAQ** [Official text from Umweltbundesamt (DE)](https://www.umweltbundesamt.de/en/topics/health/commissions-working-groups/german-committee-on-indoor-air-guide-values) The standard ## What the Indoor CO₂ Guideline Is The guideline provides bands rather than a single hard limit, so that ventilation can be judged on a scale from good to poor. The banding is given in the limit table on this page. Limit values ## UBA CO₂ Limit Values Every value Umweltbundesamt (DE) publishes for the parameter below, with its averaging period, as the standard states it. [**Carbon Dioxide (CO₂)** Gases & VOCs](https://aethair.io/parameters/co2/) **1000 ppm** *Indoor concentration* < 1000 ppm: hygienically acceptable **2000 ppm** *Indoor concentration* > 2000 ppm: hygienically unacceptable Who it applies to ## Who Uses It Schools, offices, meeting rooms, lecture halls, gyms, and other densely occupied spaces use the CO₂ guideline to check that ventilation keeps pace with the number of people present. Facilities managers, building-services engineers, teachers, and occupational-health advisers use it to decide when to open windows, increase mechanical ventilation, or reduce occupancy. Interest broadened sharply after the COVID-19 pandemic, when CO₂ became a practical, inexpensive indicator of how well a room is ventilated and therefore of the risk of airborne transmission. Monitoring ## How Monitoring Demonstrates Compliance Carbon dioxide is measured continuously with a **non-dispersive infrared (NDIR) sensor**, the reliable and stable method for indoor CO₂, and the reading is compared against the guideline bands in the limit table on this page. Because CO₂ rises and falls with occupancy through the day, continuous logging is what makes the guideline useful: a monitor shows the concentration climbing as a room fills and confirms that ventilation brings it back down. Carbon dioxide is one of the core parameters the Aethair family of indoor monitors measures in a single built-in device, so it is typically tracked alongside temperature, humidity, PM2.5, and TVOC, so ventilation adequacy and overall air quality show in one view. [Customize this configuration](https://aethair.io/build/?params=co2) ### Who measures each parameter | Parameter | Aethair PRO | Aethair IAQ | External | | - | - | - | - | | [Carbon Dioxide (CO₂)](https://aethair.io/parameters/co2/) | CO₂ (dual NDIR), CO₂ (self-calibrating NDIR) cartridges | Built in | [2 instruments](https://aethair.io/parameters/co2/) via Thiamis | Devices ## Devices That Cover UBA CO₂ How much of this standard one Aethair monitor covers, followed by the third-party instruments in the sensor catalog that measure its parameters. Each connects to Environet through a Thiamis gateway, which adds whatever the monitor leaves out. Aethair monitors [**Aethair PRO** Built in + Aethair CO₂ (dual NDIR) Covers it](https://aethair.io/products/pro/) [**Aethair IAQ** Built-in sensors Covers it](https://aethair.io/products/iaq/) Covers it on its own [**Particles Plus** Particulate & Dust Monitors](https://aethair.io/sensors/particles-plus-particulate-dust-monitors/) [**RAE** Gas Detectors](https://aethair.io/sensors/rae-gas-detectors/) Solutions ## Solutions Judged Against UBA CO₂ ### [HVAC & Building Management](https://aethair.io/solutions/hvac-building/) Monitor ventilation and filtration, with data for your BMS ### [Indoor Air Quality](https://aethair.io/solutions/iaq-monitoring/) Offices, schools, homes, and public buildings ### [School Air Monitoring](https://aethair.io/solutions/education/) Classroom CO₂, particulates, and campus IAQ [All solutions](https://aethair.io/solutions/) Questions ## UBA CO₂ FAQ Why is CO₂ used to judge ventilation rather than health? At the concentrations reached in ordinary occupied rooms, CO₂ mainly indicates how much exhaled air has accumulated, which mirrors how much fresh air is being supplied per person. High CO₂ therefore flags inadequate ventilation (and the build-up of odors, bioeffluents, and potentially airborne pathogens) long before CO₂ itself would affect health. What is the Pettenkofer number? It is the roughly 1000 ppm indoor CO₂ value proposed by the hygienist Max von Pettenkofer in the 19th century as the threshold of acceptable indoor air. It remains the classic reference, and the UBA guideline builds on it by banding concentrations above and below it from acceptable to unacceptable, as shown in the limit table on this page. Why did CO₂ monitoring become popular after the pandemic? Because CO₂ is a simple, low-cost stand-in for how well a room is ventilated, and better ventilation lowers the risk of airborne disease transmission. Placing a CO₂ monitor in a classroom or office gives an immediate, visible cue to open windows or boost airflow when a space becomes stuffy. How do I monitor indoor CO₂? Use a continuous monitor with an NDIR CO₂ sensor placed at head height away from direct breath, logging through the occupied day. The Aethair family measures CO₂ alongside temperature, humidity, and particulates in one device. Use the configurator to choose the right configuration for your rooms.