A variety of organic compounds are found in the indoor air. Aldehydes and volatile organic compounds (VOCs) are chemicals categorized with boiling points from 50–100 °C to 240–260 °C; therefore, they can be found indoors in the gaseous phase. Formaldehyde is a dominant aldehyde found indoors. Because of its known hazardous properties for humans, there are guidelines to prevent health risks established by the World Health Organization (WHO)-Europe. Studies have shown a positive association between high levels of formaldehyde and VOCs indoors and sick building syndrome occurrences, respiratory symptoms of which include asthma and wheezing. Most studies were conducted in residential housing or buildings, schools, and offices. One intervention study supported the effect of installing either a Heat Recovery Ventilator or an Energy Recovery Ventilator. This increased the mean ventilation rate and therefore reduced the levels of formaldehyde and VOC in the indoor air.