SoC: GigaDevice gd32f103rct6
CO2: SenseAir S8 LP (400–2000ppm Accuracy CO2 ±40ppm ±3%, Up to 10000ppm extended range) (30$)
PM2.5: Plantower PMS3003 (14$)
hydrogen and carbon monoxide: Figaro tgs2600 - pdf (7$)
Accum: 3.7v Li-Ion 3000 mAh 963760P