Electric Deodorization

Electrically generated deodorizing involves the use of some type of electrically operated machine or device, which performs the deodorizing process. Electrically generated deodorizing may be achieved in at least two specific ways:


Electronic air purification systems achieve their air cleansing and deodorizing effect by filtering air through an electrically charged grid or scrubber. When larger airborne microorganisms (pollen, some fungi) pass through the electrically charged filtration system, they are, quite literally, burned up. Smaller microorganisms and VOCs may be filtered from air by fine mesh and activated charcoal filters or sorbents. The option to purchase and install such a system is usually in the hands of the structure owner and, therefore, is not commonly a technique used by professional deodorizing contractors.

However, with some of the “high efficiency particle air” (HEPA) filtration units used in HVAC restoration work, coupled with activated charcoal filters, deodorization technicians are able to achieve basically the same or greater extent of particle (99.97% of all particles down to 0.3 microns) and odor removal. Unfortunately, this procedure concentrates on airborne odor only and does nothing to remove the odor at its source. On the other hand, it may be desirable for removing particulates in fire restoration claims that may cause respiratory hazards during cleaning and deodorization procedures.


Ozone is an unstable combination of three atoms of oxygen. It is formed by exciting molecular oxygen (O2) into atomic oxygen (O, or single atoms) in an energized environment that allows the recombining of three oxygen atoms to form ozone (O3). At ambient temperatures, ozone is a blue colored gas, but at the concentrations generated for deodorization purposes, color is not apparent.

Ozone is produced by nature in two ways. First, and most commonly known by the average person today, is the production of ozone in the upper atmosphere by ultraviolet rays from the sun. As sunlight enters the upper atmosphere and encounters oxygen molecules (O2), the ultraviolet end of the light spectrum excites and disassociates them into individual atoms. Those free atoms of oxygen then recombine forming a three-part oxygen molecule – ozone! In turn, the ozone layer dissipates approximately 80% of the ultraviolet rays coming from the sun, which function prevents sunburn, skin cancer and even blindness in humans.

Is it any wonder that scientists are worried about ozone depletion caused by long-lasting, chlorofluorocarbon gases (e.g., Freon®) collecting in the upper atmosphere?

The second way in which ozone is produced in nature is by strong electrical charges passing through the atmosphere in close proximity to the earth. This electrical charge is called lightning. The same disassociation and recombination of oxygen atoms (revised 1994) occurs, which accounts for the fresh smell in the air following a thunderstorm. That’s partly because the rain has “washed” the air of many particles, and partly because of the fresh fragrance of residual ozone.

The first recorded use of ozone by man was as a disinfectant for drinking water in the Netherlands in 1893. Today it is used for many purposes such as: in aquaculture for sea water purification stations, and for input water disinfection at freshwater hatcheries and fish farms; for disinfection of recycled water in large marine aquaria; for treatment of discharged water in fish disease labs; for treatment of cooling water in heating and cooling units to prevent the buildup of fungi, bacteria and algae slimes; for sterilization of ultra-pure water used in integrated circuit processing; for treatment of spent lubricants for recycling purposes; for sterilizing of high purity waters used in the pharmaceutical industry; and for preservation of meats, fruits and cut flowers during storage or shipment.

Generally, ozone is known to be a more effective bactericide, fungicide and virucide than chlorine compounds. In many European countries, ozone, rather than chlorine, is the primary agent for water purification. This applies to drinking water as well as to water used in pools and spas where human consumption or contact is anticipated.

Because of the instability of gaseous ozone, it cannot be generated and stored for later use. Consequently, ozone needs to be generated on-site for deodorization, disinfection and even sterilization purposes.

There are several types of ozone generators on the market today. Some use ultraviolet radiation above 2000 Angstroms in wavelength from unshielded fluorescent bulbs to produce ozone, as does the sun in the upper stratosphere. The majority use the corona discharge system as the means of ozone generation.

In corona discharge ozone generation, electricity, the intensity of which is controlled by a rheostat, is relayed to a transformer where a relatively low-voltage charge is transformed into a high-voltage charge. The high-voltage electricity then flows to one or more electrodes separated by an insulator. The unit produces ozone gas, O3, by drawing molecules of dry air, O2, through electrodes separated by a ceramic or glass plate. The electrodes, or conductors (usually screens), are charged with high voltage static electricity. The electricity’s attempt to jump between wires comprising the metal screens results in “sparks” of electrical current passing over the entire surface of that grid, forming a blue “corona.” When a fan draws air through the ozone generating unit, these sparks of static electricity excite themolecules of oxygen, O2, causing them to disassociate into individual atoms of oxygen, (O). The disassociated atoms then recombine forming a three-part molecule – ozone! Production of ozone by these units is enhanced by cool temperatures, and since ozone is heavier than air, it collects at floor level.

Ozone effectively and permanently destroys odor through oxidation. When ozone comes in contact with an organic odor or odor-causing microorganism, the extra atom of oxygen is imparted and oxidation of the odor (chemical “burning” in layman’s terms) takes place. The result of the oxidation reaction is a little moisture (H2O), a molecule of oxygen (O2) and some nitrogen dioxide (NO2), which accounts for a somewhat pungent smell that remains when ozone is used extensively on heavy organic odor situations for prolonged periods. If this pungent smell is a problem, it may be eliminated by light area fogging of a compound containing fragrance and chemical pairing agents.

The advantage of ozone gas is that it is clear and colorless (in use concentrations), has relatively little residual odor, although concentrations above 1.0 ppm may produce a sulfur-like odor. It is quite inexpensive to use after the initial equipment investment. Limitations include the need to use ozone in minimally occupied areas, since high concentrations result in respiratory irritation. Also, its ability to oxidize latex and to combine with moisture to form a bleach (hydrogen peroxide) that might discolor some damp fabrics after prolonged exposure in high concentrations (above 1.5 ppm), must be anticipated.

Much controversy has surrounded ozone generators since they were first introduced to the deodorizing profession for widespread use in the late sixties. As you would imagine, much of the controversy came from chemical manufacturers who saw ozone deodorization as a replacement, rather than a supplement, to chemical deodorization techniques. The fact that ozone even survived its critics is a tribute to its effectiveness as a valid deodorizing technique. Those who experimented with ozone in the early days were simply amazed at its ability to remove odor quickly and efficiently, especially when delicate or moisture sensitive fabrics (clothing, draperies, etc.) and surfaces (unfinished wood, canvas paintings, paper goods, etc.) were involved.

Today the tables are turned, and many ozone equipment manufacturers would suggest that ozone generation is the only system required. Again, we must realize that, in heavy or persistent odor situations, combining chemical deodorizing techniques and systems with ozone generation is essential for fast, effective and permanent deodorization. And today, the ozone generator has become the most essential and frequently used tool of the professional deodorizing technician.

There has been much confusion surrounding the use of ozone gas, particularly with regard to ozone toxicity. The American Council of Governmental Industrial Hygienists (ACGIH) and the Environmental Protection Agency (EPA) have determined that the Threshold Limit Value – Time Weighted Average (TLV-TWA – a safe level of ozone exposure for an eight-hour day, forty hours per week) is 0.1 (one-tenth) parts per million (ppm) of air volume (0.04 ppm, Canadian). E.R. Plunkett, in his Handbook of Industrial Toxicology, specifies a maximum eight-hour exposure level of 0.1-0.2 ppm. Since the concentration of ozone required for deodorization and for fungus and mildew inhibition is 0.3-1.5 ppm, it is obvious that in most cases ozone deodorization procedures will exceed the EPA’s TLV-TWA when prolonged exposure is anticipated. For this reason it must be used in unoccupied, controlled access areas only.