Background - Daily short-term exposure to ambient fine particles (PM₂.₅ ; < 2.5 μm) in the general environment has been related to acute respiratory effects such as respiratory symptoms and inflammation, emergency room visits for respiratory conditions and mortality. Although exposure is higher in trade/occupational settings, acute respiratory effects of daily exposures remain unexplored. Objective - To evaluate the association between daily exposures to fine particles (PM₂.₅) and Ultrafine Particles (UFP; < 0.1 μm), and fractional exhaled nitric oxide (FeNO), a relevant indicator of lung inflammation, in two trade settings from a construction school. Method - A repeated-measure panel study was carried out on students performing welding and bricklaying activities (n=30). PM₂.₅ and UFP concentrations were measured daily (area measurements with direct-reading instruments) and fractional exhaled FeNO were measured two times per day, pre-work and post-work, for 5 consecutive days. Mixed GLM models were used to assess associations. Results - Daily geometric mean exposure to PM₂.₅ from welding and bricklaying activities were respectively 183 μg/m³ (σg=3.5) and 90.8 μg/m³ (σg=1.6). Daily geometric mean UFP concentrations for these activities were 106,000 (σg=1.6) particles/cm³ and 4,400 (σg=1.7) particles/cm³. Combining bricklaying and welding activities, for a 10,000 particles/cm³ increase in UFP, there was a 0.2 ppb (95%CI: 0.05-0.3) increase in FeNO inter-day. There was also a tendency for a small increase in FeNO (0.2 ppb; 95%CI: -0.06 - 0.5) per 100 µg/m³ of PM₂.₅ . Further analyses will be performed with additional participants and stratified by occupational trade. Conclusion - Bricklaying and welding activities expose workers daily to PM₂.₅ and UFP that may contribute to recurrent pulmonary inflammation and impair respiratory health. Keywords: particulate matter, occupational exposures, short-term exposure, pulmonary inflammation.