Disinfection and sterilization of biological clean rooms

Disinfection and sterilization are two different concepts. The disinfection and sterilization methods commonly used in biological clean rooms were compared, and three common methods such as ultraviolet sterilization, formaldehyde and ozone disinfection were elaborated. Keywords UV formaldehyde ozone disinfection.

1、Introduction

According to the data, the human body can carry about 1 to 104 kinds of bacteria every 6 to 7 square centimeters of the skin, about 1% of which are pathogenic, and humans breathe and speak bacteria. Obviously, it is crucial to prevent the generation of bacteria, remove and eliminate the presence of bacteria in cleanrooms, especially those with relatively high cleanliness requirements. Disinfection and sterilization are two effective methods to remove and destroy bacteria and ensure microbiological requirements in biological clean rooms.

2、disinfection and sterilization are two different concepts

Disinfection and sterilization are two different concepts. The so-called sterilization is to kill or remove all microorganisms (including bacteria, viruses, etc.) in the substance, which has absolute significance. That is to say, the sterilization is not sterilized, and there is no intermediate state in which the sterilization is more or less. In this respect, absolute sterilization is almost non-existent because it is difficult to achieve or reach an infinitely long time.

The so-called disinfection is the way to kill most pathogenic microorganisms or reduce them to a certain extent. In the process, some bacteria or viruses are not destroyed due to resistance to heat or medicine, which has a relative significance. That is to say, the disinfectant itself has a certain sterilization range.

It is not difficult to see that the relative and absolute understanding of disinfection and sterilization is different from our usual understanding. What we usually call "sterilization", to be precise, should be called "sterilization."

3、common methods of disinfection and sterilization

Disinfection and sterilization, from the mechanism point of view, nothing more than four: dry heat method, damp heat method, drug method, electromagnetic radiation method. From these four basic methods, a variety of disinfection and sterilization methods with different application ranges and different effects are derived.

3.1 Common sterilization methods

Commonly used sterilization methods are: high temperature drying sterilization, high pressure steam sterilization, gas sterilization, filter sterilization, radiation sterilization and the like.

3.2 Commonly used disinfection methods are: boiling and atmospheric steam sterilization, low temperature disinfection, ultraviolet radiation disinfection, pharmaceutical disinfection and so on.

4、ultraviolet sterilization

Ultraviolet radiation is a kind of electromagnetic radiation method, which is widely used in local clean workshops, but its effect is limited. Article GMP of WHO GMP (1992 edition) expressly states: "Because of the limited effect of ultraviolet light, it should not be used instead of chemistry. Disinfection." Article 17.65 states: "Final sterilization, UV irradiation cannot be used."

4.1 Factors affecting the effectiveness of UV disinfection and sterilization

The factors that affect the effectiveness of UV disinfection are:

(1) Lamp use time: The sterilizing power of the UV lamp decreases with the increase of the use time. Generally, the output power after the UV lamp is used for 100h is the rated output power, and the lighting time when the UV lamp reaches 70% of the rated power is average. life. The average life of domestic UV lamps is generally around 2000h.

(2) Environmental conditions: Generally, the ultraviolet lamp has the best sterilization effect under the conditions of ambient temperature of 20 ° C and relative humidity of 40 to 60%. When the temperature is 0 ° C, the sterilization effect is less than 60%.

(3) Irradiation distance: Within 500mm from the center of the tube, the intensity of illumination is inversely proportional to the distance, while above 500mm, the intensity of illumination is approximately inversely proportional to the square of the distance.

(4) Species: Due to the different membrane structure and shape of the cells, the bactericidal effect of ultraviolet rays on the strains is different. If the product of the irradiation intensity and the irradiation time is assumed to be the irradiation dose, when the required dose of Escherichia coli is 1, about 1 to 3 of Staphylococcus, Mycobacterium tuberculosis, etc., Bacillus subtilis and its spores and yeasts It takes 4~8, and the mold needs about 2~50.

(5) Installation method: The penetration rate of ultraviolet light is low, which is greatly affected by occlusion and installation methods. In the biological clean room, there are generally several installation methods of chandeliers, side lamps and ceiling lamps, among which the sterilizing effect of the ceiling lamps is the best.

Due to the limitation of the ultraviolet sterilization effect and the destructive effect on the human body caused by sterilization, it is rarely used to fully sterilize the biological clean room by using ultraviolet lamps. Only some rooms or partial sections such as locker rooms and laundry rooms have applications. . At present, ultraviolet disinfection is commonly used in the combination of HVAC systems for gas phase circulation sterilization.

4.2 gas phase cycle disinfection

Gas phase circulation disinfection is to take some measures to allow the air to circulate through the effective irradiation area of the ultraviolet lamp in an organized manner. While increasing the irradiation time and the irradiation intensity, the ultraviolet rays do not leak people and do not generate ozone, so the ultraviolet lamp It can be used without shutting down, and the disinfection effect is greatly improved.

5、formaldehyde disinfection

Formaldehyde disinfection is a kind of disinfection of drugs, and it is also a common method used in the disinfection of biological clean rooms. There are two kinds of formaldehyde disinfection: one is disinfection on the spot, only a small range of disinfection of the clean room's local space, can be directly evaporated indoors (or heated evaporation), the effect is poor, and the detoxification after disinfection is inconvenient. The other is combined with the HVAC system. The formaldehyde overflows from the jacketed disinfection tank into the air supply unit of the air conditioning unit and is then sent to the clean room. In order to increase the evaporation intensity of the formaldehyde, the steam in the sterilization tank jacket is steamed.

It should be noted that since formaldehyde contains a large amount of formic acid and is corrosive to galvanized air ducts, it is recommended to use a stainless steel tube.

6、ozone disinfection

Ozone disinfection is a newly developed method of disinfection. The utility model has the advantages of convenient use, safety, flexible installation and obvious disinfection effect of killing bacteria.

Ozone disinfection requires the installation of an ozone generator. Ozone generators can be installed in a variety of ways: desktop, mobile or split, placed directly in the clean room where disinfection is required; ducted, can be installed in the return and return air mains of the HVAC system (where the duct needs to be expanded); In addition, the ozone generator can be fixedly installed at the rear end of the efficiency filter of the air conditioning unit. The latter two installation methods, while internally disinfecting the clean room, also disinfect the air duct, filter, and internal equipment of the HVAC system.

At present, ozone generators used in clean room disinfection have been produced by many manufacturers in China. The amount of ozone that needs to be consumed when ozone disinfection is used in a biological clean room (or the ozone generator to be used for water discharge) can refer to the relevant manufacturer's information. 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 filter materials when it is combined with HVAC system.

7、conclusion

(1) Disinfection and sterilization are two different concepts.

(2) The choice of disinfection and sterilization methods should be based on the decoration, equipment and materials of the biological clean room, production characteristics, etc., and consider the corrosiveness and economy of the disinfectant, etc., the convenience and safety of the method. The feasibility of GMP verification is comprehensively determined.

(3) Formaldehyde and ozone are two commonly used disinfection methods. Ozone disinfection is recommended in the GMP Validation Guide.

(4) In any case, it should be used in conjunction with the clean room HVAC system. For residues that are harmful to humans after disinfection, they should be diluted to a safe concentration by means of ventilation.

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