There's a lot of talk about outdoor pollution. Much less about indoor air quality in our homes, even though that's where we spend 90% of our time. Indoor air can be two to five times more polluted than outdoor air, according to the WHO. And in most cases, we don't know it.
An air quality sensor changes that. It makes the invisible visible, and lets you act at the right time rather than living in a discomfort whose origin you don't understand.
What a Sensor Measures
CO2 (carbon dioxide): probably the most important indicator for daily comfort. We exhale CO2. In a poorly ventilated room with several people, levels rise quickly. Above 1000 ppm, concentration becomes noticeable: fatigue, headaches, difficulty concentrating. Above 2000 ppm, it's significantly unpleasant. The solution is simple: open a window. But the sensor tells you when it's necessary.
Humidity: between 40% and 60% relative humidity is the comfortable and healthy zone. Below that, dry air irritates mucous membranes and promotes virus spread. Above that, mold and dust mites proliferate. A humidity sensor coupled with a connected humidifier or dehumidifier can maintain this range automatically.
VOCs (volatile organic compounds): emitted by paints, household products, plastics, building materials. Some are harmless at low doses, others are concerning. A VOC sensor alerts you when levels rise after painting, cleaning, or using certain products.
PM2.5 (fine particles): high-end sensors also measure suspended particles. Particularly useful if you cook a lot (cooking smoke is a major source of PM2.5) or if you live in an urban area.
The Concrete Health Impact
This is not an abstract concern. High CO2 in the bedroom affects sleep quality, even if you don't consciously feel it. Studies have shown a clear correlation between CO2 above 1000 ppm during sleep and lighter sleep, more frequent awakenings, and increased morning fatigue.
Similarly, too-high humidity in the bedroom promotes dust mites — a major trigger for allergy or asthma sufferers.
Choosing a Sensor
Important criteria:
- Electrochemical or NDIR CO2 sensor: NDIR (non-dispersive infrared) sensors are more accurate and durable than electrochemical sensors. An important distinction if you're buying for measurement quality.
- Built-in screen or app: a screen lets you see values at a glance without taking out your phone. Practical in a conference room or living space.
- Smart home integration: models compatible with Alexa, Google Home or HomeKit allow voice alerts and integration into automations.
What You Do Once You Have a Sensor
In the first few weeks, you often just observe. The numbers you see are often surprising. The kitchen after sauteing onions, the living room after two hours of meetings with colleagues, the bedroom in the morning before opening the window.
Then you start adapting your behavior: opening windows more systematically, airing out after certain activities, monitoring humidity in winter with the heat on. The sensor doesn't do the work for you, but it gives you the information to do it at the right time.
