The air people breathe has a significant impact on their health, comfort, productivity, and well-being. Indoor air is important because it is where most exposure to airborne contaminants occurs. However, it is not always possible to know the composition of contaminants in indoor air, its variability, and changes over time, so suitable metrics are needed to regulate indoor air, and its quality improved efficiently, sustainably, and at the lowest possible cost, along with its relationships with health risks or comfort. To improve indoor air quality, source control, targeted ventilation, and space ventilation are the most effective intervention strategies, in that order. However, increasing the ventilation rate is not always a solution, especially in highly polluted cities. In many Latin American countries, there is a lack of understanding about the problems caused by poor air quality. This is aggravated by the prevalence of fuel poverty. Poor IAQ has an unavoidable impact on government spending on health care, social care, and social security. This chapter describes metrics for determining the most important airborne contaminant sources in Latin American buildings, the variables that affect IAQ, and how contaminants may be controlled and regulated to minimize their impact on a population’s health and well-being.