Duct-Cleaning Using Biocides and Ozone Treatments

Cleaning air ducts has become a common method of reducing the amount of indoor air pollution. There are a number of methods that air duct service providers can use to clean ducts. One method is the use of Biocides and Ozone treatments.

Moisture and humidity in a duct can be a breeding ground for such biological contaminants as mold, mildew, fungi, and bacteria. Some air duct cleaning service providers will use chemical biocide or ozone to kill these organisms.


Ozone is a highly reactive gas that is regulated as a lung irritant. According to the Environmental Protection Agency (EPA),

Ozone is a very corrosive and toxic gas which is harmful to humans in any concentration. Available scientific evidence shows that at concentrations that do not exceed public health standards, ozone has little potential to remove indoor air contaminants.

This means that to be effective at removing chemicals or preventing and killing microorganisms, the amount of ozone that would need to be used would be dangerous to humans and animals. Ozone concentrations of five to seven parts per million are needed to kill microorganism contaminants that reside in the ducts. Because of the health risks, people and animals should stay away from a building until the ozone levels have normalized. Exposure can harm the lining of lung tissue and it can also be a carcinogen. Using ozone as a duct cleaning method tends to be more popular with businesses and industry than residential homes. An air duct cleaning service can come to a building on a Friday after the office has closed for the weekend and clean the ducts using ozone. This would allow for enough time for ozone levels to return to normal. Some duct cleaning companies are promoting high concentrations of ozone as an effective duct cleaning method. High concentrations have been shown to kill dust mites, bacteria, and mold.


Some duct cleaning services may use chemical biocides to kill microorganism contaminants such as bacteria and fungi. They apply a biocide to the inside of the ducts that is designed to kill microbiological growth. This is a very effective method of killing bacteria, fungi, viruses, and mold. There are some health concerns about using this type of method. Because biocide is a chemical, it should not be inhaled as it is a lung irritant and carcinogen. When using a biocide, occupants should stay away until the cleaning has been complete and the ducts are complexly dry. This will prevent chemicals from being blown through rooms where they could be inhaled and cause illnesses. Chemical biocides tend to be more popular for business and industry.

Ozone cleaning methods and the use of biocides should be utilized with extreme care and only if approved for that purpose by EPA. Chemical biocides are regulated by EPA under the Federal Pesticide Law. A product must be registered by the EPA for a specified use before it can be legally used for that purpose. The specific uses must appear on the label, as well as other essential information. Federal law requires that pesticides only be used for their specified purpose.

The EPA and most experts do not normally recommend the use of biocides and ozone as a method of cleaning duct systems unless they have been specifically approved. A small number of products are currently approved by the EPA. When properly used by a trained professional, biocides and ozone can be an effective way of cleaning ducts. Because of the health hazards, more care has to be taken when using the products. Make sure the service technician explains the health and safety measures they employ before they start cleaning.