The HALO Smart Sensor measures CO₂ (Carbon Dioxide) from two sensors; CO2cal and CO2eq. CO2cal is its own individual sensor that takes a calibrated reading of CO2. It is taking a true direct reading of carbon dioxide within the environment and contributes to Air Quality Index (AQI) and the Health Index calculation. The CO2eq reading is an indirect measurement of carbon dioxide by finding the equivalent value based on other gases such as hydrogen. The CO2eq reading contributes to Vape and THC events. 

CO2 concentration provides a measure of what percentage of the air we inhale consists of air that has already been exhaled by other people, this is called the Rebreathed Fraction. An elevated rebreathed fraction equals a greater probability of the spread of infection.

Mens virkningerne af høje niveauer af CO2 længe har været anset for at være godartede, har forskning fundet ud af, at koncentrationer så lave som 1,000 ppm kan påvirke menneskers kognitive funktion og beslutningstagning.

Den største kilde til indendørs CO2 er mennesker selv, da det er et biprodukt af vores åndedrætsfunktion. Sammen med dårlig ventilation fører dette almindeligvis til høje niveauer af CO2 på mange arbejdspladser.

The easiest way to resolved high CO₂ levels is to open the windows in a room until the levels decrease to as safe level (1,000 ppm or less).