Air pollution monitoring is one of the most important features in contamination risk management. This is because many of the compounds contained within air pollution present a serious risk both for the preservation of open air cultural heritage and for human health. New particle formation is a major contributor to urban pollution, but how it occurs in cities is often puzzling. As more and more people enjoy an increased quality of life through outdoor activity, managing outdoor air quality is vital. This study presents the application of a low-cost system for monitoring the current level of road traffic passengers’ exposure to particulate air contamination. The global rise in tourism also leads to apprehension about its probable destructive influence on various aspects of global preservation. One of the major risks encountered by tourists, stemming from modes of transport, are nanoparticles (NPs) (≤100 nm) and ultra-fine particles (UFPs) (100–1000 nm) consisting of potentially hazardous elements (PHEs). This study examines Steen Castle, a medieval fortress located in Antwerp, Belgium. Significant NPs with PHEs, were found in the air sampled in this area. The self-made passive sampler (LSPS) described in this study, consisting of retainers specially designed for advanced microscopic analysis, is used for the first time as a simple way to characterize the surrounding atmospheric contamination caused by NPs and UFPs, without the need of other commonly employed more expensive particulate focused active samplers such as cascade impactors. This study aims to assess the result of the utilization of a low-cost, LSPS, to determine outdoor NPs and UFPs in a Belgian urban (Steen Castle) and rural area (Fort van Schoten). This work is the first to detail the usefulness of LSPS for the evaluation of Belgium’s outdoor air for NPs and UFPs, which contain PHEs.