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Welding fumes are a main source of occupational exposure to particulate matter (PM), besides gases and ultraviolet radiations, that involves millions of operators worldwide and is related to several health effects, including lung cancer. Our study aims to evaluate the exposure to fine and ultrafine airborne particulate in welding operators working in a steel making factory.In October 2019, air monitoring was performed for four days in five different welding scenarios and in the external area of a steelmaking factory to assess the exposure to airborne particles, ultrafine (UFP) particulate and inhalable fraction, during welding activities. The airborne particles distribution as particle number and mass concentration were measured using a low-pressure electric impactor, model ELPI™ (range of sampling 0.006 μm and 10 μm), whereas the airborne inhalable fraction was collected by filtration, using the IOM Sampler selector.The particle concentration, i.e. the number of particles per cm3 (part/cm3) showed significantly higher exposure figures for nanoscale particles, especially for the fractions included in the last 4 stages sampled by ELPI (from 0.010 μm to 0.071 μm), the figure representing between 85 % and 91 % of the total, whereas for the last 7 stages (0.010 μm–0.314 μm), they represented from 98 % to 99 % of the total. The average figure was approximately 5.01 × 104 part/cm3, while the maximum average was 1.95 × 105 part/cm3 on TIG welding, with a peak of 1.52 × 107 parts/cm3. In terms of mass concentration, the levels of PM inhalable fraction ranged between 0.1 mg/m3 and 1.08 mg/m3.The results of the present study substantially confirm previous studies regarding the distributions in terms of number and mass of welding fumes for SMAW and TIG techniques on steel, the mass concentration levels resulting within the permissible exposure limits (PEL) indicated by OSHA regulations. The results highlighted the importance of the efficiency of localized aspiration systems and the need to apply prevention and protection measures despite the low levels of exposure measured in terms of mass. Conclusion: Overall, The particle number concentrations showed an important contribution in the emission of UFP compared to background levels. The PM inhalable fraction was substantially contained within the PEL. Further studies are needed to better understand the chemical characterization of the particulate also considering further variables of the working process that could influence the levels of exposure to welding fumes.