Laying hen houses are a known source of fine particulate matter (PM10), but no information is available on the contribution of outdoor runs to the overall emissions. This study aims to investigate some of the main factors driving PM emissions from outdoor runs. A wind tunnel device was built to assess the effect of hen density (HD, hens m−2) on PM emissions from outdoor runs. Moreover, a laboratory trial, using a soil resuspension chamber, was conducted to describe the influence of soil moisture on the emissions. The gathered information was then used to estimate PM10 emissions over a 1-year period. PM emissions increased exponentially with increasing HD and decreased exponentially with increasing soil water content. The average PM10 emissions from hen activities at the study farm, estimated using meteorological data from year 2019, were of 8.9 mg hen−1 d−1. This emission is much lower than those reported by previous studies for indoor hens rearing.