Ozone Disinfection technical specifications and GB 28232 "Safety and Sanitation Standards for Ozone Generators":

Air disinfection: Ozone has an obvious killing effect on microorganisms in the air. Using ozone at a concentration of 20mg/m3 for 30 minutes, the killing rate of natural bacteria can reach more than 90%.

Surface disinfection: Use ozone gas to disinfect. Ozone can kill the contaminated microorganisms on the surface of the article, but the effect is slow. Generally, 60mg/m3, relative humidity ≥70%, and 60 min～120min can be used to achieve the disinfection effect.

Verification Guidelines:

When disinfecting, close the corresponding fresh air inlet and return air discharge valve, so that the entire disinfected clean area air will circulate through the air duct of the purification system, and the ozone generator will start to work. If air sterilization is performed daily, it can generally be turned on for 1 to 1.5 hours; if ozone is used to replace chemical reagent fumigation to sterilize surfaces, walls, floors and equipment every week, it can generally be turned on for 2 to 2.5 hours.

For airborne bacteria, the ozone sterilization concentration is (2～4)×10^-6; for the sedimentation bacteria on the surface of the object, it is (10～15)×10^-6

After designing and applying ozone sterilization for 60 minutes to reach a relative concentration, continue to maintain for a period of time (1～1.5h) to achieve the purpose of killing bacteria settled on the surface of machinery, equipment and buildings.

The use of Ozone Gas is another alternative for gassing small or large scale operations. Ozone is made by adding high voltage to oxygen. The system uses a high concentration of ozone gas that bintegrates a gas generator to emit the Ozone to the area to be decontaminated. Normally the design specifications for the system included an ozone gas concentration of 200 ppm or more, relative humidity of 80% or more, and a treatment time that is determined by the size of the area, the inherent bioburden and the obstructions contained within the area. These systems have been employed in many industry settings and are now being considered as a possible alternative for GMP operations.

Whenever chemical agents are used for large-scale gassing or fogging of clean rooms, safety concerns must be addressed. All of the agents discussed can result in injury or death of personnel if proper precautions are not taken to ensure the containment of the chemical agent to the intended areas.

For many of the agents discussed, residues that are left behind on product-contact surfaces are also a significant concern and must be evaluated.

Although these methods of decontamination are effective, they should not be used to replace a routine program for cleaning and disinfecting the clean room areas. If they are used as the standard practice, they should be validated to demonstrate their ability to achieve an appropriate level of bioburden reduction. This should be performed taking into consideration the material of construction present in the clean room areas.

It is also important to consider the source of these organisms, for gassing will only remove what is present and may leave behind moisture, allowing for further proliferation if the causative agents have not been removed from the area.

Residual concentration after ozone disinfection

GB/T18883 "Indoor Air Quality Standard": 0.16mg/m3

Conclusion:

The requirements for ozone disinfection concentration conditions at home and abroad are completely different. The domestic "disinfection technical specifications", national standards and verification guidelines all aim to achieve a 90% kill rate of ozone disinfection. Therefore, only a lower concentration (20mg/ m3); and some foreign companies are more expecting that ozone can replace other chemical disinfectants such as formaldehyde to achieve a disinfection effect of at least 3 logs, so the disinfection concentration is relatively high (200ppm, ≈400mg/m3). Users also need to consider conditions such as the tolerance of the workshop equipment to select a suitable disinfection program.