Advances in nanostructured chemiresistive sensors for formaldehyde detection

), selectivity, operating temperature (from 250-350 °C to 80-150 °C), humidity resistance and detection limits. In addition, critical assessment of morphology modification (0D-3D architecture) and the role of noble-metal decoration in modulating surface charge transfer and accelerating adsorption-desorption kinetics typically shows a reduction of response/recovery cycles by 20-60%. Emerging strategies such as light activation, plasma treatment, vacancy engineering, and gas treatments to enhance sensor metrics have been studied for their role in stabilizing sensor performance in humid and variable environments. The integration of machine learning (ML) is also discussed as a complementary approach to improve selectivity (>90% class accuracy), optimizing feature extraction, and enabling predictive modelling of sensor behaviour across varying temperatures, humidities, and interfering gases. Finally, the review outlines current challenges and envisages future opportunities toward scalable, humidity-resilient, and intelligent chemiresistive platforms for next-generation HCHO monitoring. By uniting nanoscale material design with intelligent data analytics, next-generation chemiresistive sensors are poised to transition from laboratory prototypes to robust, scalable technologies that address urgent societal needs in environmental monitoring and public health.