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The 24-h continuous measurements of carbon dioxide (CO2) levels in 10 dental treatment rooms with various ventilation rates. CO2 accumulation occurred in rooms with lower ventilation rates (air change per hour [ACH] ≤6). CO2 levels stayed under 800 ppm in rooms with a higher ventilation rate and lower number of persons. CO2 level in nonworking hours is close to that of outdoors at 400 ppm in all rooms.
