Why are air pollutants' (PM10, PM2.5, CO, etc.) concentration guidelines (like WHO, EPA, Singapore, etc.) higher in indoors than outdoors?

Hello.Please explain why the guidelines for air pollutants concentrations are higher in an indoor environment than in an outdoor environment.Like in case of PM10, 50µg/m3 (24-hr mean) for indoor...

31 January 2023 9,493 1 View