Background: Occupational exposure to environmental tobacco smoke (ETS) is still occurring in the hospitality industry and the instance of non-compliant smoking areas required investigation. A designated smoking area covered by a roof where more than 50% of the perimeter of that part is surrounded by one or more walls is deemed a non-compliant smoking area. This study aimed to gather evidence of non-compliances across Dublin, determine current employee exposure whilst also measuring PM2.5 concentrations within smoking areas as well as providing insight into possible immediate health effects of ETS exposure. Methods: Seventy-five smoking areas (41 located in high, 27 in medium and 7 in lower socioeconomic areas) were visited from May 2019 – October 2020. PM2.5 was recorded using a SidePak AM510 Personal Aerosol Monitor for a period of 45 minutes – 1 hour inside the smoking area. Observational forms recorded physical and contextual variables of the smoking areas including, number of smokers present, roof, perimeter boundary, size, time of day and food service. Ten healthy non-smoking volunteers (5 males, 18 – 53 years old, 5 females, 21 – 58 years old) partook in spirometry assessments pre, during and post exposure to ETS within a smoking area. Results: Sixty per cent of smoking areas were non-compliant, with higher average PM2.5 concentrations than compliant smoking areas (41.1 μg/m3, 17.2 μg/m3, (p < .001)). The overall distribution of venues demonstrated that non-compliance was evenly distributed across the county. Average PM2.5 was significantly higher in smoking areas where a roof of any kind was present (36 μg/m3, no roof = 16.3 μg/m3, (p < .001)). Employees were noted working within 88% of the smoking areas visited and permanent auxiliary bars were present in 21.3% of smoking areas surveyed. When immediate effects of ETS exposure were assessed, peak flow results were suggestive of an effect between both pre exposure and during exposure (p = 0.051) as well as pre exposure and post exposure (p = 0.057). Conclusions: Widespread non-compliance with smoke-free legislation is occurring across Dublin hospitality venues and the presence of auxiliary bars in smoking areas is placing employees at risk.