Background After North Carolina (NC) fire inspectors detected unsafe carbon monoxide (CO) levels inside several waterpipe cafés, the state fire code was amended to include provisions regulating waterpipe cafés, adding a requirement for air ventilation. These regulations apply to new buildings constructed after 1 January 2016, but can be enforced for older buildings where there exists a distinct hazard to life. We measured air quality at a sample of waterpipe cafés before and after the starting date of this regulation and collected information on presence of air ventilation.

Methods Air quality (CO, fine particulate matter (PM_2.5)) monitoring was conducted inside and outside of six waterpipe cafés in NC in September of 2015 (time 1) and September of 2016 (time 2). In addition, questionnaires were administered to managers from each waterpipe café at time 2 to determine the presence of air ventilation systems.

Results Elevated levels of CO and PM_2.5 were found inside waterpipe cafés at time 1 (median CO=42 ppm; median PM_2.5=379.3 µg/m³) and time 2 (median CO=65 ppm; median PM_2.5=484.0 µg/m³), with no significant differences between time periods (p>0.05). Indoor levels were significantly higher than levels outside cafés at both time periods (p<0.05). All waterpipe cafés reported having an air ventilation system that was installed prior to time 1 air monitoring.

Conclusions Unsafe levels of CO and PM_2.5 were observed in waterpipe cafés in NC, despite reported use of air ventilation systems. Prohibiting indoor waterpipe smoking may be necessary to ensure clean air for employees and patrons.