The CrowdPM Node is a mobile environmental sensing device capable of measuring PM2.5 particulate matter concentrations and tagging each reading with precise time and location data using GPS. The device aggregates samples locally and transmits either summarized or raw data via Wi-Fi to the CrowdPM backend platform (a CS capstone project), where results can be visualized and analyzed on a map. The purpose of this system is to enable dense, crowdsourced air-quality mapping that captures small-scale variations often missed by fixed monitoring stations. Traditional air-quality networks provide only coarse spatial coverage, overlooking localized pollution from traffic corridors, construction, and transient events like wildfire smoke or diesel plumes. The CrowdPM Node addresses this gap by providing a low-cost, portable solution that empowers citizens, researchers, and municipalities to collect real-time, location-aware data.