Objectives: The purpose of the present study was to monitor and evaluate CO2 levels in dental operatories using a consumer-grade CO2 sensor and determine the utility and accuracy of various methods using CO2 levels to assess ventilation rate in dental clinics . We aim to find a practical tool for dental practitioners to conveniently and accurately monitor CO2 levels and assess the ventilation rates in their office in order to devise a pragmatic and effective strategy for ventilation improvement in their work environment .

Methods: Mechanical ventilation rate in air change per hour (ACHVENT) of 10 dental operatories was first measured with an air velocity sensor and air flow balancing hood . CO2 levels were measured in these rooms to analyze the effects of ventilation rate and number of persons in the room on CO2 accumulation . Ventilation rates were estimated using natural steady state CO2 levels during dental treatments and experimental CO2 concentration decays by dry ice or mixing baking soda and vinegar . We compared the differences and assessed the correlations between ACHVENT and ventilation rates estimated by steady states CO2 model with low (0.3 L/min, ACHSS30) or high (0.46 L/min, ACHSS46) CO2 generation rates, by CO2 decay constants using dry ice (ACHDI) or baking soda (ACHBV), and by time needed to remove 63% of excess CO2 generated by dry ice (ACHDI63 %) or baking soda (ACHBV63 %).

Results: ACHVENT varied from 3.9 to 35.0 with a mean of 13.2 ({ +/-} 10.6) in the 10 dental operatories . CO2 accumulation occurred in rooms with low ventilation (ACHVENT [≤] 6) and more persons (n> 3) but not in those with higher ventilation and less persons . ACHSS30 and ACHSS46 correlated well with ACHVENT (r=0.83, p=0.003), but ACHSS30 was more accurate for rooms with low ACHVENT . Ventilation rates could be reliably estimated using CO2 released from dry ice or baking soda . ACHVENT was highly correlated with ACHDI (r=0.99), ACHBV (r=0.98), ACHDI63% (r=0.98), and ACHBV63% (r=0.98). There were no statistically significant differences between ACHVENT and ACHDI63% or ACHBV63% .

Conclusions: Dental operatories with low ventilation rates and overcrowding facilitate CO2 accumulations . Ventilation rates could be reliably calculated by observing the changes in CO2 levels after a simple mixing of household baking soda and vinegar in dental settings . Time needed to remove 63% of excess CO2 generated by baking soda could be used to accurately assess the ventilation rates using a consumer-grade CO2 sensor and a basic calculator.