Ventilation Assessment by Carbon Dioxide Levels in Dental Treatment Rooms
Qirong Huang, Tamer Marzouk, Razvan Cirligeanu, Hans Malmström, Eli Eliav, Yan Ren
Abstract
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.