Knowledge!Disinfection and Sterilization of Biological Cleanrooms

According to the information, the human body can carry 1~104 bacteria for about every 6~7c㎡ of skin, of which about 1% is pathogenic, and human breathing and speech will also emit bacteria. Obviously, the clean plant, especially the relatively high cleanliness requirements of biological clean room, to prevent the production of bacteria, remove and eliminate the presence of bacteria is essential. Disinfection and sterilization are two effective methods to remove and eliminate bacteria and ensure the microbiological requirements of biological clean rooms.

Commonly used sterilization methods

Commonly used sterilization methods include: high-temperature dry sterilization, autoclave sterilization, gas sterilization, filter sterilization, radiation sterilization and so on.

Commonly used sterilization methods

Boiling and atmospheric steam sterilization, low-temperature sterilization, ultraviolet irradiation sterilization, pharmaceutical sterilization, and so on.

UV sterilization

UV irradiation, a type of electromagnetic radiation method, is mostly used in localized clean plants, but its effectiveness is limited, and WHO’s GMP (1992 edition), Article 17.34, explicitly states, “Due to its limited effectiveness, UV light shall not be used as a substitute for chemical sterilization.” Article 17.65 states, “For final sterilization, UV irradiation cannot be used.”

Factors that affect the effectiveness of UV disinfection and sterilization are:

(1) Lamp use time: the bactericidal power of the UV lamp with the increase in use time and decline, in general, UV lamps use 100h after the output power for the rated output power, UV lamps point to 70% of the rated power when the lamp time for the average life. Domestic UV lamp average life expectancy is generally about 2000h.

(2) environmental conditions: in general, the ambient temperature at 20 ℃, relative humidity of 40 ~ 60% of the conditions, the best sterilization effect of ultraviolet lamp. Temperature of 0 ℃, the sterilization effect is less than 60%.

(3) irradiation distance: within 500mm from the center of the lamp, the irradiation intensity is inversely proportional to the distance, while above 500mm, the irradiation intensity is approximately inversely proportional to the distance squared.

(4) Strain: Due to the different membrane structures and shapes of bacteria, the bactericidal effect of ultraviolet light on strains of bacteria, that is, the bactericidal rate is also different. If the irradiation intensity and the product of irradiation time is assumed to be the irradiation dose, when the dose of E. coli for 1, staphylococcus, tuberculosis and so on, about 1 to 3, Bacillus subtilis and its spores and yeasts and so on, about 4 to 8, molds and so on, about 2 to 50.

(5) Installation: The penetration rate of ultraviolet light is low, and is greatly affected by the shielding and installation methods. In the biological clean room, there are generally chandeliers, side lights, top lights several installation methods, including the top light of the sterilization effect is the best.

Due to the limitations of ultraviolet sterilization effect and sterilization may lead to the destructive nature of the human body, the use of ultraviolet lamps for comprehensive sterilization of biological clean room has been rarely used, only individual rooms or local sections such as locker rooms, laundry room, etc. have been applied. At present, UV sterilization is commonly used in HVAC systems combined with the gas-phase cycle disinfection.

Vapor Phase Circulation Sterilization 

Gas-phase cycle disinfection, is to take certain measures to allow the air organized circulation flow through the effective irradiation area of the ultraviolet lamp, in order to increase the irradiation time and irradiation intensity at the same time, the ultraviolet rays are not leaked to hurt people and do not produce ozone, so that the ultraviolet lamp can not be turned off to use, to achieve the purpose of the cycle of air disinfection, disinfection effect is also greatly improved.

Formaldehyde sterilization

Formaldehyde disinfection is a kind of pharmaceutical disinfection, but also a common way of disinfection in the current biological clean room. There are two kinds of formaldehyde disinfection: one is in-situ disinfection, only a small range of disinfection of the local space of the cleanroom, formaldehyde can be used to evaporate directly indoors (or heating evaporation), the effect is poor, and the disinfection of the detoxification is inconvenient. Another is combined with the HVAC system, formaldehyde from the disinfection tank with a jacket overflow into the air conditioning unit of the air supply point of the main pipe and then sent into the clean room, in order to increase the intensity of evaporation of formaldehyde, disinfection tank jacket with steam.
It should be noted that, due to formaldehyde contains traces of formic acid, and galvanized ducts and other corrosive, it is recommended that the use of stainless steel pipe.

Ozone sterilization

Ozone disinfection, is a newly developed disinfection method. It is characterized by easy to use, safe, flexible installation, and obvious disinfection effect of killing internal bacteria.

Ozone sterilization requires the installation of an ozone generator. The ozone generator can be installed in a variety of ways: desktop, mobile or split type, placed directly in the clean room to be disinfected; pipeline type, can be installed in the HVAC system of the supply and return ducts (where the ducts need to be enlarged); in addition, the ozone generator can be installed in the purification of air-conditioning units fixed at the back end of the intermediate-effect filters. The latter two installation methods, within the clean room for disinfection at the same time, the HVAC system ducts, filters, internal equipment, etc. also play a role in disinfection.

At present, the ozone generator used in clean room disinfection has been produced by a number of domestic manufacturers. The amount of ozone required to be consumed when a biological clean room is sterilized by ozone (or the ozone generator to be used is the output of water discharge) can be referred to the information of the relevant manufacturers. Compared with formaldehyde disinfection, the advantage of ozone disinfection is that it is easy to install, and it is non-corrosive to air ducts and filtering materials when it is used with HVAC systems.

Conclusions

(1) Disinfection and sterilization are two different concepts.

(2) The choice of what kind of disinfection and sterilization, according to the biological clean room decoration, equipment and its materials, production characteristics, etc., and take into account the corrosiveness of disinfectants and other corrosive, economic, the convenience of the way, safety and GMP verification of the feasibility of a comprehensive determination.

(3) Formaldehyde and ozone are two commonly used disinfection methods. The GMP Validation Guide recommends the use of ozone disinfection.

(4) Regardless of the method, it should be used in conjunction with the HVAC system of the cleanroom. For the disinfection of the residue harmful to people, it should be promptly diluted to a safe concentration through the ventilation device.

(5) Any disinfection method and disinfectant have a certain degree of drug resistance, and should be replaced after a period of use.