{"id":997602,"date":"2026-10-29T08:00:00","date_gmt":"2026-10-29T07:00:00","guid":{"rendered":"https:\/\/kienzler-klima.de\/?p=997602"},"modified":"2026-08-19T11:24:33","modified_gmt":"2026-08-19T09:24:33","slug":"how-to-measure-co2-levels-indoors-reliably-and-affordably","status":"publish","type":"post","link":"https:\/\/kienzler-klima.de\/en\/how-to-measure-co2-levels-indoors-reliably-and-affordably\/","title":{"rendered":"How to measure CO2 levels indoors reliably and cheaply?"},"content":{"rendered":"
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Measuring indoor CO2 levels reliably and affordably is easy with a simple CO2 meter based on NDIR sensor technology. Devices in this category are available starting at around 50 to 100 euros and deliver sufficiently accurate readings for most use cases in offices, schools, and commercial spaces. The following sections answer the most important questions about measurement technology, device selection, and placement.<\/p>\n

At what CO2 level does indoor air quality deteriorate?<\/h2>\n

Indoor air is considered noticeably worse at a CO2 concentration of around 1,000 ppm (parts per million). Outdoor air typically contains around 420 ppm CO2. Between 800 and 1,000 ppm, the ability to concentrate measurably decreases; above 1,400 ppm, many people experience headaches, fatigue, and reduced cognitive performance.<\/p>\n

The workplace guideline ASR A3.6 is based on the Pettenkofer value of 1,000 ppm as a benchmark for acceptable indoor air quality. The Committee on Indoor Air Guide Values of the German Federal Environment Agency classifies values between 1,000 and 2,000 ppm as hygienically concerning, and values above 2,000 ppm as unacceptable. For workrooms, school classrooms, and public buildings, a target value of below 1,000 ppm is therefore recommended. Those who understand the fundamentals of air distribution<\/a> will quickly see why a uniform supply of fresh air is essential to maintaining this threshold on a permanent basis.<\/p>\n

How does a CO2 meter work technically?<\/h2>\n

Most indoor CO2 meters operate using the NDIR method (Non-Dispersive Infrared). Infrared light passes through a measuring chamber containing room air. CO2 molecules absorb infrared radiation at a characteristic wavelength, and the device calculates the CO2 concentration in ppm from the measured attenuation.<\/p>\n

NDIR sensors are considered the most reliable method for indoor air measurement because they respond directly to the CO2 molecule rather than to proxy variables such as VOCs (volatile organic compounds). Lower-cost devices sometimes rely on electrochemical sensors or MOX sensors, which only estimate CO2 indirectly. These so-called eCO2 values are less suitable for reliable indoor air quality measurement. For any serious application, whether in an office or in food production, a genuine NDIR sensor is the right choice.<\/p>\n

What is the difference between a CO2 traffic light and a CO2 data logger?<\/h2>\n

A CO2 traffic light displays the current CO2 level in real time via a color signal \u2014 typically green, yellow, and red. A CO2 data logger, on the other hand, records measurements over a defined period of time, enabling the analysis of trends and patterns.<\/p>\n

Both device types have their place, depending on the application:<\/p>\n