CO2 Sensor Calibration Guide

Short Answer: Use Outdoor Air as a Reference

Take the sensor outdoors, let it stabilize for 5 to 10 minutes, and confirm the reading is between 400 and 450 ppm. If the value is outside that range, recalibration is recommended.

Recommended Outdoor Calibration Check

1. Bring the sensor outdoors on a mild day and keep it at least 6 feet (2 meters) away from people, vehicles, windows, doors, and exhaust sources.
2. Leave it powered on for 5 to 10 minutes so the reading can stabilize.
3. Confirm the CO2 value is in the expected outdoor range of 400 to 450 ppm.
4. If the reading is outside that range, recalibrate according to the product instructions or contact VisiblAir for help.

When Recalibration Is More Likely to Be Needed

• The sensor has been dropped, shocked, or transported roughly.
• You see a persistent mismatch versus trusted reference devices.
• The unit was previously calibrated indoors in an occupied or poorly ventilated space.
• The product is used in demanding environments where accuracy matters for classrooms, offices, or inspections.

Common Calibration Mistakes

• Calibrating indoors: occupied rooms often have elevated CO2, which can force the sensor to adopt the wrong baseline.
• Checking too close to people or cars: exhaled breath and engine exhaust can push readings upward.
• Not waiting long enough: a sensor needs a few minutes outdoors before the reading settles.