Choosing an Indoor Climate Monitor: CO₂, Temp, Humidity
Indoor climate monitors track CO₂, temperature and relative humidity and warn before the air turns stale. This guide explains sensor types, sensible limit values and alarm setup to DIN EN 16798 for office and production.
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Which parameters matter for indoor climate?
An indoor climate monitor records at least three variables: CO₂ concentration, air temperature and relative humidity. CO₂ is the best indicator of stale air, because it rises with occupancy and measures how well fresh air is supplied.
Fresh outdoor air sits at around 420 ppm CO₂. In occupied rooms air up to 1000 ppm counts as hygienically good, while above 1400 ppm it is clearly stale. Temperature and humidity additionally govern thermal comfort and the risk of mould or dry mucous membranes.
- CO₂: lead indicator for ventilation need and occupancy density.
- Temperature: 20‑26 °C depending on season for comfort.
- Relative humidity: 40‑60 % prevents dry air and mould.
- Optional: particulate matter, VOC or sound level for extended monitoring.
What limit values apply under DIN EN 16798?
DIN EN 16798‑1 rates indoor air quality by the CO₂ rise above outdoor air and sorts it into four categories (IDA/Cat I-IV). Category II is a normal, good level and allows roughly 800 ppm CO₂ above the outdoor value.
In practice this means: with around 420 ppm outdoor air, the target for offices is about 1000 ppm (Cat II). For temperature the standard gives comfort ranges of roughly 21‑23 °C in winter and 23‑26 °C in summer, and for humidity a comfortable corridor of 30‑70 %, in practice aimed at 40‑60 %.
How do you set up alarms sensibly?
A monitor is only useful if it warns in time. The simplest solution is the CO₂ traffic light with green-yellow-red. In addition, devices can sound an audible alarm or send values over the network to a building management system or dashboard.
- Green up to 1000 ppm: air quality good, no action needed.
- Yellow 1000‑1400 ppm: plan a burst of ventilation.
- Red from 1400 ppm: ventilate immediately, reduce occupancy.
- Humidity alarm below 30 % or above 60 % relative humidity.
- Data logging for records and trend analysis.
What to check on sensor and calibration?
Key factors are sensor type, accuracy and calibration capability. A good NDIR CO₂ sensor reaches ± 30‑50 ppm plus 3 % of reading, a humidity sensor ± 2‑3 % relative humidity and a temperature sensor ± 0.3‑0.5 °C.
- Automatic baseline calibration (ABC) for stable CO₂ readings.
- CO₂ range up to at least 5000 ppm for production use.
- Interfaces: display, relay, Modbus or WLAN/LAN.
- Wall mount at 1.1‑1.5 m height, not next to a window or door.
Frequently asked questions
At what CO₂ ppm should I ventilate?
As a rule of thumb: from about 1000 ppm yellow (plan to ventilate) and from 1400 ppm red (ventilate immediately). These marks follow DIN EN 16798 category II and the Pettenkofer number.
Why is an NDIR sensor better than an eCO₂ sensor?
NDIR measures CO₂ directly via infrared absorption and is suitable for a standard-compliant assessment. eCO₂ or VOC sensors only calculate the value from other gases and drift strongly.
What relative humidity is ideal in an office?
A range of 40 to 60 % is optimal. Below that, mucous membranes dry out; above it, the mould risk rises on cold surfaces.
Does production have a different CO₂ limit?
Yes, the occupational exposure limit is 5000 ppm. For concentration and comfort, climate sensors warn well below that, usually from 1000 to 1400 ppm.
Looking for the right climate monitor?
We supply CO₂ traffic lights and climate data loggers with NDIR sensor, alarms and interfaces - assessable to DIN EN 16798.
NDIR precision
Direct CO₂ measurement instead of estimated eCO₂ values.
Standard reference
Limit values assessable to DIN EN 16798.
Alarms included
Traffic light, buzzer and data logging out of the box.
Expert advice
We help with selection and calibration.