HISTORY AND GENERAL STATEMENT
The first ozone installation was made by Siemens Company (Germany) in 1857. (Ref. 151. p 17) Complex molecules can be broken down by the powerful oxidation effect of ozone. Ozone can react with compounds that cannot be broken down by biological agents (bacteria) or otherwise integrated into the biological process for further processing.

EFFECTS ON BACTERIA AND VIRUSES
Effects on Bacterial Aerosols
Aerosols were produced by spraying bacterial suspensions at 20 lb/sq. in pressure and concentrations of bacteria were in the range of 50-500 viable organisms per liter of air. The killing effect of ozone was determined by comparing the curves for decay with, and without, ozone. Ozone concentrations ranged from 2.0 p.p.m.v. down to 0.025 p.p.m.v. Tests were performed on three organisms; Streptococcus salivarius, Streptococcus ‘C’ and Staphylococcus albus. The role of humidity in the action of ozone, particularly when the gas is at low concentration, was apparent. At humidities less than 45%, ozone, even in high concentrations, exerts no appreciable disinfecting action on bacteria. For humidities above 50%, however, ozone reduced the bacteria count. In fact, ozone as low as 0.025 p.p.m.v. showed definite bactericidal action at 60 to 80% humidity.

Bacteria That Have Settled on Surfaces
Bacteria on surfaces constitute a potential infection danger as a source of infection through re-dispersal in the air or contact with skin or clothes. Tests were made to determine whether ozone has any disinfecting action on deposited bacteria. Bacteria were sprayed on various surfaces: agar in Petri dishes; Whatman filter paper; sterile glass Petri dishes and wool cloth. These were placed in known conditions of humidity (range 60-85%), temperature and ozone concentration. After being exposed. the bacteria were counted and compared with surfaces having bacteria not exposed to ozone. Ozone in a concentration of 0.02 p.p.m.v. in a moderately humid atmosphere exercises a very definite killing effect against bacteria on surfaces, but below this level it has little effect.
The kill depends on (a) the “depth” and type of surface; so moist agar. Whatman #1 filter paper and wool cloth are more favorable to survival than glass or #50 Whatman paper; (b) resistance to ozone of different types of bacteria: Staphylococcus albus resistance is greater than Streptococcus Salivarius, which in turn is greater than B.prodigiosus.

Discussion
Ozone, in concentrations up to 0.04 p.p.m.v. in humid atmospheres exerts a disinfecting action on certain bacteria; Streptococcus salivarius. Streptococcus ‘C’, Staphylococcus albus and B. prodigious. Tests on E. coli with up to 1 to 2 p.p.m.v. in relatively dry air failed to destroy any organisms. This confirms ozone is a poor disinfectant at low humidities. However, at humidities above 60% tests confirmed pathogens can be destroyed by minute amounts of ozone. (Ref. 158)
Increasing the moisture content of the environment favorably influences germicidal effect. This is brought about by swelling of microbes making them more susceptible to destruction.

ODOR CONTROL
Ozone is unmatched as a deodorizer. Ozone has a strong characteristic odor even in very low concentrations. Its effect on the olfactory membrane makes it difficult or impossible to detect other odors when ozone is present. In low concentrations (0.01 to 0.02 p.p.m.v.) ozone acts as a masking agent on most odors. Tests have demonstrated that room odors were undetectable even when ozone concentrations were less than 0.01 p.p.m.

Some very delicate odors are destroyed even at these low concentrations. However, to totally eliminate “heavy” odors higher concentrations of ozone are required to react with gases in the air and odors trapped in materials. Time to deodorize is determined by the quantity of the substance producing odor and the quantity of ozone available to react with it.

Ozone at a concentration of 0.1 p.p.m.v will destroy microorganisms and eliminate most odors within 48 hours.

Odoriferous substances are susceptible to oxidation, but the addition of oxygen to a substance (oxidation) does not always render it safe. For example, oxidation of allyl alcohol yields aldehyde acrolein, a very deadly gas. Safety considerations apply only to definite industrial odors and do not include animal wastes or putrefactive gases of animal or vegetable tissue. Putrefaction produces highly odorous substances such as amino, aromatic and fatty acids, indole, skatole, cresol, and also the alkaloid-like ptomaines, such as tetramethylene-diamine and pentamethylene- diamine, etc. The effect of ozone on these substances is that of combustion; i.e., the final products of the hydrocarbons being C02 and water and those containing nitrogen, nitrogen pentoxide.

Where putrefaction occurs – the air from sewers, etc.- while highly odoriferous, contains but traces of these substances. The odors are easily and completely destroyed by ozone. Ozone has been used in San Francisco to deodorize a sewage pumping station when the pump screens had to be cleaned. A rat died in a wall of an office building and the odor penetrated several offices. The application of ozone completely destroyed the odor.

Single atoms of oxygen from the decomposition of ozone immediately oxidize odors. The lower the temperature and the larger the odor molecules, the weaker the oxidizing effect. Humidity has no effect on this process but does accelerate the destruction of bacteria, viruses, and fungi that may contribute to odor.
Portable, compact ozonators have been used successfully in the following areas:

• Garbage Holding areas
• Bus, train, aircraft, and vehicle interiors
• Employee lounges
• Fish stores (fish odors will not cling to clothing)
• Hotels – smoke odors, spilled beverage or food odors, urine, and fecal odor, vomit, individual body odors
• Restaurants, cocktail lounges, and bars
• Kitchen and food preparation areas
• Restrooms
• Health clubs, swimming pools, spa rooms, and sports locker rooms
• Heat pump and air conditioning installations eliminate “Dirty Sock Syndrome” (odor)
• Chlorine smell control
• Restoration of buildings, drapes, curtains, furniture, rugs, and clothing
• Veterinary clinics, zoos, indoor animal farm areas
• Hospitals, nursing and retirement homes
• Office buildings
• Retail stores
• New construction and restoration – Ozone eliminates paint, carpet, furniture and paneling odors – toxic outgassing, principally Formaldehyde
• Funeral homes – body transport, storage, and preparation: vehicles

THE SMELL OF OZONE

Ozone at low concentrations (0.01 to 0.04 p.p.m.v.) leaves a fresh and pleasant feeling to a room. At high ozone concentrations, a characteristic “electrical” odor is noticeable.

STERILIZING

Ozone at ambient temperatures is the only substance that can be used as a total sterilizing agent and a substitute for high temperatures. Pyrogens, byproducts of microbial growth that are toxic to humans, are not eliminated after normal autoclaving or dry heat sterilization. Pyrogens adhere firmly to surfaces of containers and are removed only after heating at very high temperatures for extended periods of time. Because pyrogenic material is a lipopolysaccharide, the unsaturated double bonds are easily oxidized by ozone. Therefore, ozone has a distinct advantage over other dehydrogenation methods.

BIOCLEAN ROOMS

Ozone can be used to decontaminate Bioclean Rooms.