Given that humans spend 80% of their lives indoors, good indoor air quality is of paramount importance. In this chapter, we examine the indoor air pollutants of most concern and the need for indoor air quality standards. PM2.5 particles are of greatest concern, followed by VOCs, especially those which are carcinogenic. We suggest that indoor air quality standards for PM2.5 and toxic VOCs should mirror those for outdoor air quality. We rely on the chemical and solvent businesses to define a labelling system for other VOCs rather than have unnecessary legislation imposed.