These compounds are found in many common household products. Since the VOC's are small molecules and in some cases can exert a high vapor pressure, leakage from what might seem to be a tightly closed container may occur. Storage should be separate from the main living area where fumes can be safely vented. The second most common gases are the combustion products from burning of materials and these include carbon dioxide, carbon monoxide and oxides of nitrogen. The carbon monoxide and dioxide gases are relatively odorless and pose the greatest danger as asphixiants.
Oxides of nitrogen can be irritants and sensitizers.
Burning of synthetic materials can evolve various toxic gases depending on the type of material. The combustion products are the result of gas ranges and stoves, water heaters, furnaces and fireplaces. Other contaminants that are potentially allergenic are natural pollens and dusts that may carry organic or inorganic toxins, bacteria, molds and insect secretions. Many pollens are natural allergens and activate sensor cells in the mucous membranes of the nose, throat and upper bronchial tract. Routes of Entry Toxins enter the body through inhalation, ingestion and skin contact.