In the present study, we assessed for the first time the performance of our custom-designed low-cost Particulate Matter (PM) monitoring devices (Atmos) in measuring PM₁₀ concentrations. We examined the ambient PM₁₀ levels during an intense measurement campaign at two sites in the Delhi National Capital Region (NCR), India. In this study, we validated the un-calibrated Atmos for measuring ambient PM₁₀ concentrations at highly polluted monitoring sites. PM₁₀ concentration from Atmos, containing laser scattering-based Plantower PM sensor, was comparable with that measured from research-grade scanning mobility particle sizers (SMPS) in combination with optical particle sizers (OPS) and aerodynamic particle sizers (APS). The un-calibrated sensors often provided accurate PM₁₀ measurements, particularly in capturing real-time hourly concentrations variations. Quantile–Quantile plots (QQ-plots) for data collected during the selected deployment period showed positively skewed PM₁₀ datasets. Strong Spearman’s rank-order correlations (r_s = 0.64–0.83) between the studied instruments indicated the utility of low-cost Plantower PM sensors in measuring PM₁₀ in the real-world context. Additionally, the heat map for weekly datasets demonstrated high R² values, establishing the efficacy of PM sensor in PM₁₀ measurement in highly polluted environmental conditions.