Sterilization: The protein of bacteria in the air is denatured by heating (dry heat, damp heat), chemical reagents (such as formaldehyde and ethylene oxide), ozone and rays (such as ultraviolet lamp irradiation) for sterilization.
Disinfection: Use filter media (such as various air filters, high-efficiency filters and other purification equipment) or electrostatic precipitator to capture and intercept dust and miscellaneous bacteria in the air.
Industrial sterilization methods are often not single, but a combination of both. For flowing air (such as HVAC system and compressed air), filter media is often used to sterilize, while for the air in static environment, sterilization method is often used to sterilize aseptic rooms, cultivation rooms, transfer windows, clothes, etc.
Although the air filtered by the high-efficiency filter in HVAC system can control the number of living microorganisms in the room within the specified range. However, in actual production, dust particles will be produced on the surface of buildings due to the operation of machines and the action of people, which will breed bacteria and are easily blown off, especially the bacterial pollution caused by people. One person emits about 1,000 dead skin cells (equivalent to 20μm particles) per hour. Therefore, the indoor building materials of the aseptic room, and the washing, drying and packaging of clean clothing must also be carried out in a clean environment; Aseptic clothing should be sterilized by high temperature; Personnel, equipment, and instruments entering the aseptic room should undergo strict disinfection and sterilization (hands need to be disinfected or sprayed); Regularly carry out indoor disinfection and sterilization. GMP of various countries has strict regulations on airborne bacteria and surface bacteria in clean rooms. For example, USP recommends that the allowable values of bacteria in clean environments are shown in the following table.
1. Bacterial allowable value
|
Cleanliness level |
Planktonic bacteria (CFU/INCH³) |
Surface bacteria (CFU/INCH³) |
Human bacteria (CFU/INCH³) |
|
|
Glove |
Other |
|||
|
100 |
1 |
3 |
3 |
5 |
|
100 and 10000 |
5 |
5/10(floor) |
5 |
10 |
|
100000 |
87 |
20/30(floor) |
15 |
30 |
During the production of sterile medical instruments, there are live microbial particles on the floor, wall, ceiling, machines and clothes surfaces of cleanrooms. When the temperature and humidity are appropriate, bacteria can multiply on their surfaces and be blown away into the room by air currents from time to time. Therefore, the clean room must have enough time for cleaning and disinfection every day.
2. Disinfection method
Common methods of surface disinfection and sterilization include ultraviolet lamp irradiation, ozone contact, fumigation with peracetic acid, ethylene oxide and other gases, disinfectant spraying, etc.
Cleaning and sterilization are the main means to remove microbial contamination, but the thoroughness of cleaning and sterilization must be ensured. Therefore, sterile medical device manufacturers must formulate cleaning and sterilization regulations and conduct regular verification to determine whether the sterilization agent and concentration, disinfection equipment and disinfection time are qualified.3. Ultraviolet lamp sterilization
Ultraviolet lamp was widely used by pharmaceutical manufacturers before other disinfection methods were used. It was mainly used for disinfection of clean workbench, laminar flow hood, material pass box, air shower room and even the whole clean room. The wavelength of ultraviolet rays is 136~390nm, and the ultraviolet rays of 253nm have the strongest bactericidal power, but the penetrating power of ultraviolet rays is extremely weak and there is a dead angle of irradiation, so it is only suitable for surface sterilization.
4. Ozone disinfection
Disinfection principle of ozone: The molecular structure of ozone is unstable at normal temperature and pressure, and it quickly decomposes into oxygen and a single oxygen atom. The latter has strong activity and strong oxidation effect on bacteria. Ozone can oxidize and decompose the enzymes necessary to oxidize glucose in bacteria, thus destroying its cell membrane and killing it. Excess oxygen atoms will recombine into oxygen molecules without any toxic residue, so ozone is called pollution-free disinfectant. It not only has a strong ability to kill various bacteria (including hepatitis virus, Escherichia coli, Pseudomonas aeruginosa and miscellaneous bacteria, etc.), but also is very effective in killing mold.
The raw materials for ozone production are mainly air and electric energy, which are generally obtained by high-frequency oxygen generator (electronic sterilizer). During disinfection, the ozone generator is placed in the room directly, and the concentration of ozone disinfection in the air is very low, which can be calculated according to the room volume and the ozone output of the ozone generator.The technical indexes of ozone generator that need to be confirmed and corrected in the verification of ozone disinfection effect mainly include ozone yield, ozone concentration and time timer, and the disinfection time is determined by verifying and checking the number of bacteria.
5. Gas sterilization
The traditional way to sterilize the ambient air is to use disinfectant to evaporate and produce gas for fumigation under certain conditions. Disinfectant is a mixture of formaldehyde, ethylene oxide, peracetic acid, carbolic acid and lactic acid, etc.
Among all disinfectants, formaldehyde is the most commonly used. When the relative humidity is higher than 65% and the temperature is 24 ~ 40℃, the disinfection effect of formaldehyde gas is the best. However, if too much formaldehyde is used, white powder will precipitate and adhere to the surface of buildings or equipment due to polymerization. When formaldehyde is used for disinfection and sterilization, the amount of gas produced, fumigation time and ventilation time should be determined by the verification results.6. Disinfectant sterilization
The walls, ceilings, doors, windows, machinery and equipment, instruments, operating desks, cars, tables, chairs and other surfaces of the clean room and human hands (gloves) should be cleaned regularly and sprayed with disinfectant during daily production. The common disinfectants are propanol (75%), ethanol (75%), leucodialdehyde and bromogeramine. The traditional disinfection method of sterile rooms in pharmaceutical enterprises in China is fumigation with formaldehyde, while in foreign countries, it is sprayed with dialdehyde. The method is to put dialdehyde in an automatic sprayer with timing function and spray it automatically when no one is present. During disinfection, the air conditioning system should stop working. Disinfectant used in sterile room must be filtered with 0.22μm membrane in laminar flow workbench before use.