Abstract Welding fumes (WF) are a complex mixture of ultrafine polymetallic particles, which can deposit in all regions of the respiratory tract. They contain high levels of transition metals (Cr, Cu, Mn …) known to catalyze the production of reactive oxygen species which are related to numerous adverse health effects. In industrial hygiene, collected WF are analyzed several days later, following usual standard techniques. However, during storage WF samples may undergo several physico-chemical modifications that may lead to an underestimation of their oxidative potential (OP) and metal bioaccessibility. In this work, we determined the influence of several usual storage conditions on the OP (dithiothreitol method OPDTT) and metal bioaccessibility of WF. Fresh WF were generated using a controlled welding bench and the collected particles were subsequently stored following various conservation conditions (temperature, atmosphere composition and durations) before analysis. OPDTT of WF significantly decrease with increasing storage duration when stored in ambient air, either at +20°C or -20°C, while there are no significant variations for storage under N2(g). Furthermore, the metal bioaccessibilities show similar trends to that of the OPDTT of WF for the tested conservation conditions. This work confirms that storage conditions of WF have an undeniable influence on their metal bioaccessibility and OPDTT. On-line analysis could offer an alternative to WF filter sampling, using OPDTT as a probe of health monitoring for exposed professionals