Where You Place Your Monitor Matters
A CO2 monitor is only as useful as its readings are accurate, and placement has a huge impact on what your sensor reports. Positioned poorly, a monitor might show reassuringly low numbers even while the occupants are breathing stuffy, high-CO2 air. Follow these guidelines for reliable data.
Optimal Placement Rules
Height
Mount your monitor at breathing height — approximately 1-1.5 metres (3-5 feet) from the floor. CO2 mixes well in indoor air, but placing the sensor too low (floor level) or too high (ceiling) can introduce small measurement errors, especially in rooms with poor air circulation.
Distance from Walls
Keep the sensor at least 30 cm (12 inches) away from walls. Stagnant air pockets near walls can give readings that do not represent the room average.
Avoid These Locations
- Next to windows or doors — drafts bring in outdoor air (420 ppm), giving falsely low readings
- Near HVAC vents — supply air is typically low in CO2, creating an unrepresentative bubble around the sensor
- Too close to faces — exhaled air is roughly 40,000 ppm and will cause wild spikes
- In direct sunlight — heat can affect sensor accuracy and display readability
- In kitchens near gas stoves — combustion produces CO2 that does not reflect overall room ventilation
Room-by-Room Recommendations
- Living room — centre of the room on a shelf or side table at seated head height.
- Bedroom — nightstand or dresser, at least 1 metre from your pillow. Monitor overnight trends for sleep optimisation.
- Office — on or near your desk, 60-90 cm from your face. See our office air quality guide.
- Classroom — wall-mounted at 1.2 metres, centre of a wall away from windows. See our schools guide.
How Many Monitors Do You Need?
Each enclosed room with its own door benefits from its own monitor, since CO2 levels can vary dramatically between rooms. As a starting point, prioritise bedrooms and your primary workspace. Use the CO2 calculator to determine which rooms are most at risk based on occupancy and size.
For help choosing a monitor, see our best home monitors guide. For tips on verifying accuracy after placement, read our accuracy verification guide.