Ozone been applied on a large scale to heating, ventilating, and air conditioning (HVAC) systems. Major reasons for this surge of interest in ozone treatment of indoor air include:

• Heightened public awareness that something can be done about indoor air quality (IAQ).
  
• Increased IAQ problems due to sealed buildings and less makeup (outside) air metered into HVAC systems.
  
• Increased public intolerance for smoking and the realization that many common chemicals contribute to poor IAQ.
  
• New ozone generator and ozone monitor designs that make system control a reality.
  
• Attractive payback economics due to savings in energy and other factors.
  

The large majority of projects so far are for gaming facilities (casinos, bingo halls, card rooms) and larger hospitality businesses including restaurants, showrooms, and bowling centers. These users have found that there is a high return on investment in systems which create and maintain high air quality. Many projects, often much smaller in scale, have been completed for cocktail lounges, taverns, airport smoking areas, and even for advanced technology facilities for animal raising on a large commercial scale.

The major objection to ozone is safety. Its concentration in public areas must be kept below harmful levels. This is accomplished by new technology ozone generation and monitoring equipment combined as a self-controlling system. There is disagreement among cognizant agencies about what are safe levels and suitable guidelines for ozone concentrations. The US FDA states a limit of .05 ppm for areas where people of all kinds congregate. Most ozonated HVAC systems with automatic controls are programmed not to exceed concentrations ranging from 0.03 to 0.05 ppm. These concentrations are below naturally occurring outdoor levels in many regions, but are just high enough to reduce VOCs significantly. Furthermore, the ozone concentrations are much higher in the supply ducts where bacteria, mold, mildew, and VOCs accumulate. For ozone injected into HVAC systems it is absolutely necessary to include ozone sensors to automatically control the ozone concentration in areas where the public congregate.

Two applications of ozone in the “hospitality industry” air quality control are:

• Casinos. Gaming facilities are proliferating worldwide and are often a part of high-end resorts. Smoking, which is very heavy in most gambling environments, is a major irritant for many customers and employees. Ozone very effectively removes the odor of cigarette smoke caused by a complex of VOCs in the smoke. A typical  20,000 square foot (2,000 square meters) is shown below. Ozone was installed in the rooftop HVAC system to replace the carbon filter beds which were not working well in the heavy smoke environment.
• The Dubai International Airport may be the largest ozonated HVAC system in the world with air treatment in all buildings. There are over 300 ozone sensor/controllers and many VOC sensor/controllers as well. There are many small ozone generators spread along the HVAC ductwork along with the ozone and VOC sensors. Virtually all interior spaces are treated including the freight terminal.
  

After operation of the system for about one year, the preliminary findings were:

• Passengers and employees note a pleasing air quality without the distinct smells that are often found in busy airports.
  
• The savings of ozone replacing carbon filters are very large. Carbon filters have high replenishment costs and occupy a lot of valuable space.
  
• The energy savings in reducing the makeup air requirement are significant.
  
• Other HVAC system maintenance costs are reduced such as less cleaning of the ducts due to virtually no mold and mildew accumulation.