Ozone Generator Used on HVAC

Configuration scheme for ozone sterilization

According to technological characterisitics of central air conditioning system, the system can be divided into centralized air conditioning system, induction system and fan coil unit air conditioning system. The specific ozone dosage method should be selected according to different type of central air conditioning.

To take advantage of central air conditioning equipment to spread ozone gas to the whole control area. Taking advantage of central air conditioning air pipeline to mix ozone gas with air in the system, at the same time, under the influence of internal circulation, ozone concentration in the air is very even. And by contacting and mixing with air in the system, it will kill the bacteria, infectious viruses and microorganisms. Eventually it will improve air quality and ensure the fitness of those who working in the environment. There is no need to increase any other disinfection equipment to achieve the purpose of sterilization and effectively killing all kinds of virus and bacteria. In practice, ozone could play the role of diverting bacteria for the HEPA filter so as to prolong its working life.

In the purification system of the pharmaceutical industry, the general application of ozone sterilization for one hour can reach the concentration requirements. To continue for about 1 to 1.5 hours, it could achieve the effect of completely killing sedimentary bacteria attached to the surface of mechnical equipment and building surface, completely replacing chemical fumigation in disinfection.

Ozone generator selection

To select the ozone generator, it is necessary to know the evaluation indicators of the ozone generator. The basic indicator to evaluate an ozone generator: ozone output, ozone concentration, reliability, working life and power consumption etc.

Ozone concentration unit:  percentage of volume concentration (according to international standard)

For sanitary disinfection industry, the common unit is PPM, that is per million by volume. Ozone concentration in the air: 1PPM = 2.14mg/m3.

If using HVAC system to dose centrally, the selection of ozone generator could adopt following methods:

First of all, to calculate actual ozone disinfection volume, it consists of three parts: V1 + V2 + V3.

V1: total volume of clean area;

V2: total volume of air supply duct;

V3: Conversion volume of complementary fresh air to maintain positive pressure of clean area

Calculation of each volume

According to several ozone generator manufacturers, a reliable formula is concluded as follow：

V2 negligible

V3≈ total air circulation volume of HVAC system m3/h*1.2%

Then to decide the cleanliness class of whole clean area. According to "disinfection technical specification" and the practical application experience,

Three hundred thousand level access C=2.55ppm

One hundred thousand level access C=5ppm

Wan take C=15ppm

Hundred level take C=20ppm

Planktonic bacteria in the air: 2--4ppm

Sedimentary bacteria attached to the surface: 10-15ppm

For example, for air sterilization of a factory, the required ozone concentration of the clean area is C= 5PPM. But in fact, clean area disinfection not only for air disinfection, but also for object surface disinfection. Thus, we set ozone concentration at 10PPM.

Engineering technical parameters

Disinfection area S= 36*48=1728 m2 elevation H=2.6m  air supply=  100000m3/h

According to the engineering parameters provided by the factory

V1=S*H=1728*2.6=4492.8m3

V2 negligible

M3 V3=100000*1.2%=1200m3

The actual ozone disinfecting volume V=V1+V2+V3=4492.8+1100=5592.8 ~ 5593 m3

Required ozone dosage W= C×V/（1-S）=10*2*5593/0.4208=286.82 g/h

Considering the influence of pipeline and other factors, the output of the ozone machine is 300g/h.

There are several methods for ozone generator installation:

a. Placed in a separate room as an individual unit;

b. Assembled in the air conditioning unit

c. Placed in the total supply air duct

d. Placed in total return pipe

e. Placed separately, only insert the exhaust port into the (back) air duct

Currently we usually adopt the fifth method. The ozone gas is produced by one unit of ozone generator which could be used simultaneously for a plurality of workshops. The procedure is as follow:

Air compressor-oxygen enricher-ozone generator-air supply duct-purification area.

Lead ozone gas to air supply main pipe with nylon tube; then utilize pressure air source produced by purification fan in HVAC system to spread ozone gas to the whole clean area. This installation method applies to newly built or rebuilt plant. For rooms without HVAC system, it can lead ozone gas directly to the room, then spread ozone gas to the room utilizing internal circulation to achieve the purpose of disinfection and sterilization.

Control mode

For ozone disinfection of central air-conditioning system, after confirmation of specific dosage location and mode, it can combine with automatic control system of central air conditioner and enable automatic disinfection function over divided period. It can also be set manually to turn on the ozone equipment, turning on the equipment manually untimed (must be operated when air conditioning system in operation) for sterilization.

Ozone disinfection replaces chemical reagent fumigation sterilization, to achieve energy-saving of air conditioning system in clean room.

GMP implementation guideline requires continual operation of air conditioner in area of cleanliness class 100 and class 10000. For clean area with non continous operation, when in non production shift, conditioning system should be on duty operation, to keep indoor positive pressure. In order to ensure the cleanliness, generally air conditioning is in continuous operation, only in this way can avoid the clean room being polluted by suspended particles and microbial contamination. Regarding disinfection and sterilization of clean room with ozone,    it could be done when the asepsis room does not work. Stop the running of all air conditioning units and turn on the fan for air disinfection and sterilization 2 hours before going to work.

Due to the use of ozone for disinfection, it can avoid the problem of secondary pollution produced by chemical fumigation, but also alleviate the pressure on the air filter, which will extend the working life of the filter, thereby saving maintenance costs.