SHORT INTRODUCTION TO OZONE AND ITS USE
What is ozone?
The Gas ozone consists of three oxygen atoms. It can be produced when energy (e.g. electrical charge) breaks a
stable molecule (O2) into two unstable oxygen (O1) atoms. These two oxygen atoms alone look for stable O2
molecules and combine them to transform into ozone (O3).
The Ozone is present in nature as a gas that has a pale sky blue color and a pungent smell and a powerful
oxidant. The ozone molecule is unstable and tends to break apart again, and this explains why ozone cannot be
stored in any way and must be produced on site with an ozone generator.
The use of ozone worldwide as a "green" sanitizer in agri-food and civil use is on the rise. In light of this, and
supported by the opinion of the CSNA of 27 October 2010, with these guidelines it is intended to update (both
from a scientific and technical point of view), the knowledge on its applications in the field of sanitization of
processing and working environments in general such as: central air treatment, offices, waiting rooms, shops,
hotels, transport, etc.,etc..
In food production facilities and workplaces in general, surface sanitization and bacterial air purification are
The current provisions on occupation by-work safety (D.Lgs. 626/94) and hygiene (155/97 H.A.C.C.P.) impose a
healthy and safe working environment. Ozone generators for disinfection and environmental pest control, to be
performed during the night or without staff. Profits for food, dairy, disinfection companies, etc. Used in
accordance with protocol 2482 of 31/07/96 of the Ministry of Italian Health
The sanitization process must be able to reach all surfaces and hotspots, distributing the sanitizer in
homogenous form, constant and safe to carry out its activity. The gaseous form is also the one that propagates
best in environments reaching areas sometimes inaccessible to operators. To reach this focus, it is very
important to use professional and efficient equipment to ensure the best application in the environment
treated. The ozone producer equipment has to be able to give the right ozone concentration and constant
uniformity in all the area treated with enough air volume and air speed.
Among oxidant agents, ozone is the third most potent after fluorine and leaky, which explains its high
Ozone is artificially produced with oxygen through corona discharge generators with an endothermal process
which requires high voltage gradients between electrodes, or uv radiation (that require high power
The reaction is reversible and, therefore, ozone spontaneously breaks down, which is why it cannot be stored
but produced on site. In addition, the half-life of the ozone molecule depends on the temperature, in fact at 20
degrees Centigrade, the concentration of ozone halves in 40 minutes, to 30 degrees Centigrade in 25 minutes,
to -50 degrees Centigrade after 3 months.
Ozone concentrations can be referred to as follows:
- 467 ppmv - 1.0 g/ml or 1.0 mg/l or 1.0 g/m3
- 1000 ppmv - 2.1g/ml or 2.1 mg/l or 2.1 g/m3
- 1 ppmv - 0.0021 g/ml or 0.0021 mg/l or 0.0021g/m3
Ozone has highly biocide and virucide properties, and compared to other disinfectants is 1.5 times more
oxidant than chlorine and 3000 times more than hypochloride acid. It is very effective, even at low
concentrations, against a wide range of microorganisms including viruses, and does not leave toxic residues or
by-products like other disinfectants.
Several studies have highlighted the antibacterial and antifungal efficacy of gas ozone as a disinfection agent in
surfaces and food processing environments and other activities where the risk of bacterial and viral
contamination may be high.
The use of ozone can be more cost-effective than using other chemicals. The costs of purchasing and
maintaining ozone units are lower when compared to the cost of supplying disinfectant products.
Gas-phase ozone is not selective. It attacks and oxidizes both the components of the biofilm and the structures
Contact with ozone in humans is inhaled, so to comply with safety parameters, the use of this
Gas should be managed in such a way as to avoid irritation to the respiratory system.
The limits of inhalation exposure to chemical agents are regulated in Italy by D.Lgs. 81/2008 which is the
legislation on safety at work. The identification of the values related to inhalation exposure with regard to
ozone should be sought in the first instance in the regulatory provisions of D.Lgs. 81/2008, in the XXXVIII and
XLII attachments, if not present in these Attachments refers to the values indicated by the American
Conference of Governmental Industrial Hygienists.
For the assessment of medical and environmental conditions it is common practice, in fact, to refer to the
threshold values (TRESHOLD LIMIT VALUES-TLV) of ACGIH.
The safety limit for workers exposed to ozone, such as TLV-TWA, is related to physical activity (as they change
volumes of aspirated air).
The values indicated by ACGIH are:
For heavy, moderate or light work, but carried out in a time frame of less than 2 hours
- the TLV-TWA is placed at 0.2 ppm, equal to 0.39 mg/m3.
For work over two hours:
- light work the TLV-TWA is placed at 0.1 ppm, equal to 0.2 mg/m3
- moderate work the TLV-TWA is placed at 0.08 ppm, equal to 0.16 mg/m3
- heavy work the TLV-TWA is placed at 0.05 ppm, equal to 0.1 mg/m3.
Cycle of sanitation treatment (GENERAL)
It should be pointed out that for sanitation with gas ozone, all treatment parameters must necessarily be
adapted to the different environmental conditions of the production realities considered. Therefore, technical
tests of distribution, concentration, homogeneity and safety must be carried out in order to transfer the use to
the operational reality.
In order to develop the treatment cycle, it is crucial to know:
- Features of the environment to be treated (open, closed, with or without staff, cubage, temperature).
- ventilation or air conditioning systems (if any), of the room's air distribution.
- Suction system, for possible expulsion or destruction of residual ozone.
Typical stages of a course of treatment are:
- Conditioning phase:
It exactly coincides with the stage at which you start injecting ozone into the room to be sanitized. This
injection is carried out in such a way as to enable the planned ozone concentration to be achieved in a
- Treatment phase:
This phase is intended to ensure the effectiveness of the cycle by prolonging the time required for
- Aeration or decay phase:
A phase that ensures the elimination of ozone from the air in the local treaty and continues until the
required ozone concentrations for worker safety are reached.