Awareness of indoor air quality has increased substantially in recent years, and the systems that supply air to our living and working spaces are critical to the maintenance of a healthy indoor environment. As a global industries, leading advocate, and trusted resource of reliable information, the National Air Duct Cleaner association is uniquely qualified to provide guidance for consumers and the industry on the best practices for inspecting cleaning and restoring HVAC systems, one topic that has generated both substantial interest and concern is the use of chemicals, Cleaners, sealants and coatings inside the air handling system. Currently a broad diversity of information exist regarding the use and efficiency of these chemical products. And working with all parties associated with indoor air quality in NADCA Recognizes the need to provide direction in this complicated and evolving area.It is generally agreed that social removal of contaminants remains the single best method for cleaning and decontaminating HVAC systems.However, chemicals may be applied within HVAC systems for a variety of reasons. Numerous types of contamination may be found within HVAC systems depending on the environment and conditions. These contaminants may contribute to mold, mildew fungal growth and other microbial logical growth. Other contaminants may include debris from outside air sources, fire, damage, residue, dust, etc. Source removal defined as a physical removal of contaminants and debris from internal HVAC system surfaces. Complete HVAC system cleaning removes the contaminants that may contribute to mold and other microbial biological growth. Cleaning can also reduce household dust, increase energy, efficiency, increase, equipment, life expectancy and improve overall indoor air quality and comfort.