Indoor air quality is the atmosphere inside and around structures and buildings. IAQ is said to affect human health, comfort, and performance. Poor indoor air quality is linked to increased sick building syndrome, decreased productivity, and lowered school learning.

Several factors contribute to the poor indoor air quality inside buildings. These factors can include increased traffic within the structure, poor indoor air quality from furnishings and equipment, increased use of toxic substances for heating purposes, combustion products, solvents, pesticides, toxic cleaning products, pest control, and poor design. Poor indoor air quality within buildings can also be caused by unbalanced heat distribution, leaks, flooring materials, excessive electrical activities, inadequate lighting, inadequate ventilation, inadequate natural ventilation, improper sealing of surfaces, windows, ducts, doors, etc. combustion products. Indoor air quality can also result from poor or decaying HVAC equipment, such as furnaces, boilers, ductwork, and heat pumps. This can contribute to adverse health issues.

The purpose of this article is to focus on the relationship between Indoor Air Quality Contaminants. Indoor Air Quality is in the air present inside a building, yet not distributed through windows, doors, or ventilation systems. Airborne Indoor Air Quality (IAQ) is defined as the number of airborne pollutants present inside a building during a survey. For example, the total level of dust in the air during a survey would be measured as " IAQ." However, IAQ does not only encompass airborne pollutants; it also includes any vapors, spores, dust mites, or allergens released into the air.

Indoor Air Quality is often measured using either the level of dust, moisture, or airborne particles present in the air. Generally, IAEQ is considered to be equal to the concentration of dust in the atmosphere. However, short-term exposure to high levels of dust can increase the incidence of asthma. Similarly, prolonged exposure to high levels of humidity, moistness, or airborne particles can negatively affect the lungs. Short-term and long-term exposure to airborne allergens and pollutants can also cause asthmatic reactions and other health conditions.

Two commonly measured Indoor Air Quality Indicators are Formaldehyde and Volatile Organic Compounds (VOC). Formaldehyde is a gaseous compound that results from the reaction between formaldehyde and certain chemical compounds such as amino acids, which react with oxygen in the air to form different molecules. Some common chemical contaminants in indoor air include benzene, ethylene, naphthalene, and petroleum-based chemicals. A common form of VOC is formaldehyde. While it is not toxic in small quantities, prolonged or repeated exposure to high levels of VOCs can produce toxins in the body, such as coughing, dizziness, skin irritation, headaches, vomiting, and chest pain.

The most common Indoor Air Quality Problems associated with poor indoor air quality are related to poor mechanical ventilation and HVAC systems. Many residential and commercial heat and air conditioning systems fail to meet Indoor Air Quality standards because insufficient ventilation is provided. If adequate ventilation is provided, the contaminants should be released from the building's contents, but this is not always the case. Furthermore, a system must be continually upgraded to maintain adequate levels of ventilation. In conclusion, inadequate ventilation is often the cause of poor indoor air quality.