ASHRAE has recognized that polluted urban air, designated within the United States Environmental Protection Agency (EPA)'s air quality ratings as unacceptable requires the installation of treatment such as filtration for which the HVAC practitioners generally apply carbon-impregnated filters and their likes. Different toxins will aggravate the human body in different ways. Some people are more allergic to mold, while others are highly sensitive to dust. Inadequate ventilation will exaggerate small problems (such as deteriorating fiberglass insulation or cooking fumes) into a much more serious indoor air quality problem. Common products such as paint, insulation, rigid foam, Particle Board, plywood, duct liners, exhaust fumes and other chemical contaminants from indoor or outdoor sources, and biological contaminants can be trapped inside by the HVAC AC system. As this air is recycled using fan coils the overall oxygenation ratio drops and becomes harmful. When combined with other stress factors such as traffic noise, poor lighting, inhabitants of buildings located in a polluted urban area can quickly become ill as their immune system is overwhelmed. Certain VOCs, considered toxic chemical contaminants to humans, are used as adhesives in all common building construction products. These aromatic carbon rings / VOCs can cause acute and chronic health effects on the occupants of a building, including cancer, paralysis, lung failure, and others. Bacterial spores, fungal spores, mold spores, pollen, and viruses are types of biological contaminants and can all cause allergic reactions or illness described as SBS. In addition, pollution from outdoors, such as motor vehicle exhaust, can infiltrate into poorly designed buildings and contribute to poor indoor air quality, high ppm of CO and CO2. Adult SBS symptoms were associated with a history of allergic rhinitis, eczema and asthma.