Urban air quality in Guinea-Bissau is a growing concern due to rapid industrialization and inadequate monitoring infrastructure. A combination of open-source hardware components and calibration methods were employed to design and test low-cost PM2.5 sensors. The sensors showed a linear relationship with PM2.5 concentrations within the range tested, with an R² value of 0.98. The developed sensors demonstrated reliability in measuring urban air quality parameters and can be utilised for cost-effective monitoring solutions. Further validation studies should be conducted to assess long-term stability and accuracy under varied environmental conditions. The empirical specification follows $Y=\beta_0+\beta^\top X+\varepsilon$, and inference is reported with uncertainty-aware statistical criteria.