The first sections of this report cover the current state of knowledge, the objectives, and the evaluation strategy (sampling and analysis) used within the framework of this field study. [...] The collected information was, among other things, the resin used, the thickness sprayed, the season during which the work was carried out, the location (indoors or outdoors), the time of the sampling (during spraying or post-spraying), the protective equipment, the scaffolding equipment (stepladder, stationary or mobile platform, with articulated arm, etc.) and the analytical results. [...] IRSST - 4,4’-Diphenylmethane diisocyanate (MDI) - Safety practices and concentration during 17 polyurethane foam spraying First, the air intake for the pump for the supplied air respirator was outside the truck, without taking into account the direction of the truck's exhaust gases, thus contaminating the air fed into the pump. [...] The average concentration was calculated using the same equation, but the denominator corresponded to the total duration of sampling for a spraying period that was the subject of the survey. [...] The average concentrations corresponding to a DAEV and the average concentrations of the samples in a spraying zone are listed by installer in Table 6. Those in the area outside of the spraying zone, corresponding to the zone where the assistants were working, are in Table 7. The lines in bold type correspond to the teams followed for a full day.