Understanding Indoor CO2 Levels
Carbon dioxide monitors measure CO2 concentration in parts per million (ppm). In occupied buildings, readings help assess how effectively ventilation removes exhaled air. Interpret results alongside occupancy, outdoor CO2 levels and ventilation conditions rather than relying on a single reading.
Choosing a CO2 Monitor
Select a monitor based on its measurement range, accuracy, response time and intended installation. Handheld meters are useful for spot checks in different rooms, while desktop and wall-mounted monitors support ongoing observation. Data logging, adjustable alarms and connectivity can help with longer-term monitoring where available.
NDIR CO2 Measurement
Non-dispersive infrared (NDIR) sensors measure carbon dioxide by detecting its absorption of infrared light. When comparing instruments, confirm that the device measures CO2 directly. An estimated CO2 value derived from another sensor is not equivalent to a direct carbon dioxide measurement.
Monitor Placement
Position the monitor where it can sample air representative of the occupied area. Avoid placing it directly beside an open window, supply vent, doorway or a person’s face, as these locations can distort readings. Follow the manufacturer’s guidance for mounting height, clearance and stabilization time.
Temperature and Humidity Monitoring
Models that also measure temperature and relative humidity provide additional context for indoor comfort and building conditions. These measurements complement CO2 readings when evaluating classrooms, offices, meeting rooms and other occupied spaces. Confirm which parameters the selected instrument measures.
Alarms and Data Logging
Adjustable alarms can draw attention to rising CO2 levels, while recorded readings help reveal patterns associated with occupancy and ventilation schedules. Review trends over representative operating periods to identify recurring conditions and assess the effect of ventilation adjustments.
Calibration and Sensor Care
Follow the instrument’s calibration procedure and recommended maintenance schedule. Automatic baseline calibration, where provided, depends on the conditions specified by the manufacturer and may be unsuitable for continuously occupied spaces without periodic exposure to an appropriate baseline. Keep sensor openings clean and unobstructed.
CO2 Monitoring and Other Air Quality Measurements
CO2 readings do not provide a complete assessment of indoor air quality or directly measure airborne pathogens. Carbon dioxide monitors also do not detect carbon monoxide unless a separate CO sensor is specified. Applications involving potential hazardous gas concentrations require equipment designed for the specific gas, concentration range and alarm requirements.
