This paper presents a case study on air quality in Central London with a focus on particulate matter (PM10 and PM2.5). The relationship between road width, traffic patterns, wind direction, building orientation, and particulate matters (PM10 and PM2.5) concentrations is explored in this experimental study via a walking journey. GPS geographical analysis and portable air quality sensors are used to assess the air quality. The key results indicate that narrower roads with high buildings in general exhibit irregular PM spikes which could be explained by trapped emissions and busy traffic. Larger roads (≥20 m in width) have presented a more stable air quality which can be explained by improved air circulation and consistent traffic flow. The results demonstrates the need for enhanced measures with specialized interventions such as the plantation of green walls and trees (green infrastructure) combined with improved traffic control. The results also indicate the importance of traffic management and the importance of policies and strategies such as London’s Urban Greening Factor (UGF), London Low Emission Zone (LEZ), Ultra Low Emission Zone (ULEZ), Congestion Charge Zone, and the support of electric transportation. The novel experimental methodology and findings presented in this paper provide a strong foundation for a broader and more comprehensive future study.