Odorox System Effect

Odorox® System Effect on Microorganisms


Atmospheric hydroxyl radicals are continuously produced in our troposphere by the action of the sun’s radiated energy. The major mode of formation is the reaction of UV radiation longer than 315nm with ozone. Shorter wavelengths are filtered out by the stratospheric ozone layer. There are, on average, two (2) million hydroxyls in each cubic centimeter of ambient outdoor air during sunny daylight hours. Even at these low concentration hydroxyls are the primary environmental oxidant and the main driving force behind the daytime reactions with hydrocarbons and inorganic gases in the troposphere and neutralize most natural and man-made pollutants including greenhouse gases like methane, hydrogen sulfide and ozone.

Atmospheric hydroxyls are also proven to kill bacteria, virus and mold because they are able to react with the lipids, proteins, carbohydrates and other organic compounds that make up the cell membrane and disrupt their structure. The interior contents of the cells leak and the organism is destroyed. Conversely, humans, animals and plants have evolved symbiotically with atmospheric hydroxyls and developed outer surfaces and mucosa that are essentially impervious to their effect. Atmospheric hydroxyls are a critical component of nature’s dynamic ability to provide environments that are free of harmful chemicals and pathogens. (D. E. Heard, “Analytical Techniques for Atmospheric Measurement”, Blackwell Publishing, 2006 – professor at the University of Leeds, UK).

Hydroxyl Radical Sanitization Process

Indoor environments do not naturally contain hydroxyl radicals as hydroxyls generated outdoors react too rapidly to diffuse indoors. HGI Odorox® systems were designed to generate hydroxyl radicals to cleanse indoor environments in a manner that is similar to how the Sun cleanses the outdoors, although the method of formation is different. Odorox® systems use custom made UV lamps (also known as optics) to generate the same broad range of UV radiation as the Sun. Since none of the radiation is filtered out, the primary pathway for Odorox® hydroxyl radical formation is the photolysis of water vapor by UV radiation. Another minor pathway is by the formation of ozone by UV, which is then immediately decomposed by UV light with a different wavelength to generate additional hydroxyl radicals. HGI’s Odorox® custom optics, patented reaction chamber design and active process controls result in the generation of safe and effective concentrations of atmospheric hydroxyls within the same concentrations as those found in nature.

The HGI Odorox® hydroxyl radicals are highly reactive and excellent radical transfer agents. They rapidly react with microorganisms and with nearly every organic chemical available. They remove a hydrogen atom and form a cascade of organic radicals that is further oxidized to form peroxy (R-CO-O·) and oxy (R-C-O·) free radicals, which are also good oxidizing and sanitizing agents. These byproducts are stable enough to circulate under the influence of high velocity fans to completely sanitize air, surfaces and porous fabrics in even exceptionally large spaces.

Atmospheric hydroxyl radicals and their peroxy and oxy by-products are unstable species which do not linger in the air or on surfaces. As long as the Odorox® system is running, the chain reactions persist. When the system is shut off, the hydroxyl radicals and other free radicals dissipate within seconds. The stable organic oxidation by-products that are formed indoor include alcohols, ketones, aldehydes and acids. These by-products are recirculated through the Odorox® photolysis chamber and are decomposed by rapid reactions with hydroxyl radicals within or near the chamber. When the systems are run continuously, as is recommended, these intermediate by-products are decomposed to yield carbon dioxide and water. The steady state concentrations of these compounds remain within the low ppb range, often near ambient levels, and do not accumulate. (Columbia Laboratories studies).

Odorox® Effect on Microorganisms On Surfaces and In Air

HGI Industries has completed a number of microbiological studies using licensed testing laboratories to evaluate the speed and effectiveness of their systems to eliminate a broad range of pathogens commonly tracked by the FDA as representative of their type. Studies were done on non-porous and porous surfaces and in air. Results from ATS Laboratories using the MDU™ system indicated that substantially all of the following microorganisms were killed on stainless steel, glass and cotton fabric within the specified times summarized below. Full reports are available on the HGI website (www.hgiind.com).
  • C. difficile – 99.8% and 98.6% within 48 hours
  • Listeria – 94.7% and 98.6% within 48 hours
  • Aspergillus niger – 99.9% and 97% within 48 hours
  • Porcine Reproductive Respiratory Syndrome (PRRS) virus – 97.9% within 6 hours
  • Pseudomonas aeruginosa – 91.9% within 4 hours
  • Influenza A virus – 99.98% and 99.9% within 6 hours
  • Methicillin Resistant Staph. Aureus (MRSA) – 65.1% and 94.4% within 48 hours
  • Klebsiella pneumoniae (CRE) - 99.4% within 4 hours and 99.9% within 8 hours
HGI also commissioned studies by Aerosol Research and Engineering Laboratories to evaluate the kill rates of aerosolized bacteria, virus and mold species by the MDU/Rx™ system (Note: MDU/Rx™ system is an MDU™ unit with a fixed fan speed with dual optics operating) under controlled conditions in a room-sized stainless steel environmental test chamber using a methodology approved by the FDA. This study assessed the efficacy of the system for each of the four (4) following aerosolized biologicals: Staphylococcus epidermidis, Erwinia herbicola, MS2 bacteriophage and Phi-X174 bacteriophage. The study consisted of a total sixteen (16) separate trials; one control run plus triplicate challenge trials for each of the four (4) aerosolized biologicals.

The MDU/Rx™ system’s efficacy of reduction of S. epidermidis viability, after correcting for control run losses, were 4.7 +/- 0.17 logs (average +/- standard deviation) in 1 hour. The system’s efficacy against E. herbicola bioaerosol, after correcting for control trial viability losses, were 4.9 +/- 0.5 log (Avg +/- STdev) in 1.5-2.0 hours trial time.

The MDU/Rx™ system’s efficacy against viral bioaerosols was similar to the vegetative cells trials. The MDU/Rx™ system’s reduction in viable bioaerosol concentrations within the chamber, after correcting for control run viability losses, were 5.0 +/- 0.35 logs and 4.0 +/-0.06 logs (Avg +/- STdev) in 2 hours or less for bacteriophage MS2 and PhiX174 respectively.

Results from the control trials were graphed to show natural viability loss over time in the chamber.
Very high kill rates of 4 to 5 log reductions were achieved within two to three hours, as summarized below. The optimum method for achieving and maintaining these levels of sanitation is to use the Odorox® systems continuously. Air movement and human contact rapidly re-contaminate air and surfaces. The dynamic action of airborne hydroxyl sanitization ensures that microorganisms continue to be killed and minimizes surface contamination and transfer.
Studies on the reduction of bacterial and fungal pathogens on plant material were also conducted using raw and sprouted barley, an important commercial product. Random samples of raw barley and fresh barley sprouts were placed in an environmental chamber and exposed to the output of an MVP14™ system placed outside of the chamber for a period of 2 to 96 hours. Samples were taken periodically and examined for the presence of live microorganisms. Within several hours kill rates in excess of 99.9% were measured by ATS Laboratories for the following pathogens. No fungal growth was isolated on any samples after 6 hours of treatment with respect to the raw sprouted barley product. Even after exposure for 96 hours no damage to the plant material was observed.

Sprouted Barley Product: (plant material was stirred every two hours and appeared unchanged
  • Aspergillus niger
  • Candida krusei
  • Trichosporum beigelii
  • Rhodotorula glutinous
  • Acinetobacter baumannii
  • Enterobacter agglomerans
  • Enterobacter clocae
  • Bacillus sp.
Raw Barley product: (plant material was not stirred)
  • Pantoea Agglomerans
  • Acinetobacter Baumanni
  • Bacillus SP
  • Psuedomonas Fluorescens
  • Penicullium Citrinum, Mucor SP
  • Fusarium SP
  • Afusarium SP
  • Aspergillus Flavus Group (GRP)
  • Aspergillus Niger GRP
  • Syncephalastrum SP (Zygomycete)
  • Pithomyces SP
Note that the hydroxyl radical does not react with carbon dioxide and would thus not interfere with normal plant respiration. Hydroxyl radicals would however, react rapidly with plant respiration byproducts like ethylene and neutralize them, which is beneficial as it minimizes spoilage.


As a category, the FDA does not regulate or require premarket 510(k) approval for UV irradiation air cleaning devices – such as HGI’s – that are used for commercial or consumer applications since they irradiate ambient air and cleanse in a manner similar to that found in nature. In medical facilities, Odorox® systems integrated with heating, ventilation and air conditioning systems may also be used without FDA approval. FDA approval, however, is required for ultraviolet air sanitizing systems used within occupied spaces in medical facilities. HGI received FDA 510(k) approval for the use of the Odorox® MDU/Rx™ system in occupied spaces in medical facilities (#133800) based on an extensive evaluation of microbiological, chemical, mechanical, electrical and radiation data that proved the system was effective and safe. The device is marketed as the Odorox® MDU/Rx™ model.

At HGI’s request the National Institute of Environmental Health Sciences searched the NIH, CDC, and OSHA databases, PubMed and the National Library of Medicine and “cannot find any hard science or research indicating that hydroxyl radical generation is harmful to human health. That applies to both atmospheric and man-made generation” (Colleen Chandler, NIEHS Office of Communications and Public Liaison, 8-5-10).

Odorox® hydroxyl systems have been in use for over ten years and no adverse effects have been reported. As a further measure to evaluate safety, HGI commissioned Comparative Biosciences (Sunnyvale, CA) to conduct toxicology studies using the FDA’s rigorous testing protocol called Good Laboratory Practices (GLP). The studies involved a control group of 20 rats and a treated group of 40 rats that were exposed continuously to 2 to 3 times normal concentrations of hydroxyls for a period of 13 weeks. The study results indicated that the test animals tolerated the exposure well with no abnormal clinical observations either at the gross or cellular level.
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