Ventilation Assessment by Carbon Dioxide Levels in Dental Treatment Rooms

It is important for dental care professionals to reliably assess carbon dioxide (CO 2 ) levels and ventilation rates in their offices in the era of frequent infectious disease pandemics. This study was to evaluate CO 2 levels in dental operatories and determine the accuracy of using CO 2 levels to assess ventilation rate in dental clinics. Mechanical ventilation rate in air change per hour (ACH VENT ) was measured with an air velocity sensor and airflow balancing hood. CO 2 levels were measured in these rooms to analyze factors that contributed to CO 2 accumulation. Ventilation rates were estimated using natural steady-state CO 2 levels during dental treatments and experimental CO 2 concentration decays by dry ice or mixing baking soda and vinegar. We compared the differences and assessed the correlations between ACH VENT and ventilation rates estimated by the steady-state CO 2 model with low (0.3 L/min, ACH SS30 ) or high (0.46 L/min, ACH SS46 ) CO 2 generation rates, by CO 2 decay constants using dry ice (ACH DI ) or baking soda (ACH BV ), and by time needed to remove 63% of excess CO 2 generated by dry ice (ACH DI63% ) or baking soda (ACH BV63% ). We found that ACH VENT varied from 3.9 to 35.0 in dental operatories. CO 2 accumulation occurred in rooms with low ventilation (ACH VENT ≤6) and overcrowding but not in those with higher ventilation. ACH SS30 and ACH SS46 correlated well with ACH VENT ( r = 0.83, P = 0.003), but ACH SS30 was more accurate for rooms with low ACH VENT . Ventilation rates could be reliably estimated using CO 2 released from dry ice or baking soda. ACH VENT was highly correlated with ACH DI ( r = 0.99), ACH BV ( r = 0.98), ACH DI63% ( r = 0.98), and ACH BV63% ( r = 0.98). There were no statistically significant differences between ACH VENT and ACH DI63% or ACH BV63% . We conclude that ventilation rates could be conveniently and accurately assessed by observing the changes in CO 2 levels after a simple mixing of household baking soda and vinegar in dental settings.