1. Definition of disinfection and sterilization
Disinfection: It is the elimination of microorganisms, germs, and viruses that are harmful to the human body.
Sterilization: Kill all microorganisms. No matter the microorganisms are harmful or beneficial to the human body.
2. Methods of disinfection and sterilization
(1) Drug method: disinfection and sterilization are carried out by wiping, spraying and fumigating with sterile drugs. These drugs are corrosive to a certain degree, so the surface to be sterilized must have good corrosion resistance.
a. Fumigation with ethylene oxide gas. 25°C, 30% relative humidity, 8~16 hours. There is a certain degree of toxicity.
b. Peroxyacetic acid. Concentration 2% spray. 25°C, 20 minutes. It is corrosive.
c. Acrylic acid gas fumigation. 25°C, relative humidity 80%. The dosage is 7g/m3. There is a certain degree of toxicity.
d. Formaldehyde gas fumigation. 25°C, relative humidity 80%. The dosage is 35ml/ m3. There is a certain degree of toxicity.
e. Formalin gas fumigation. 25°C, relative humidity 10%. 10 minutes. It is irritating.
(2) Ultraviolet irradiation: Ultraviolet generally have a wavelength of 1360~3900, and ultraviolet with a wavelength of 2537 has the strongest sterilization ability. The sterilization ability of the UV lamp will decrease with the increase of time. Generally, the output power of 100 hours of ignition is the rated output power, and the ignition time when the UV lamp is ignited to 70% of the rated power is defined as the average life of the UV lamp. If the UV lamp exceeds the average life but the expected sterilization effect cannot be achieved, the UV lamp should be replaced.
The sterilization effect of the UV lamp is also different with different strains, and the irradiation dose for killing molds is equivalent to 40-50 times the irradiation dose for killing bacilli. The sterilization effect of the UV lamp is also related to the relative humidity of the air. The relative humidity of 60% is the design value. When the relative humidity exceeds 60%, the exposure must be increased.
Ultraviolet lamp irradiation should be carried out in an unmanned state because there is certain damage to the human body. The ultraviolet lamp has a better effect of sterilizing and irradiating on the surface, but it has little effect on the flowing air.
(3) High temperature and high-pressure steam sterilization: The high-temperature dry heat sterilization temperature is generally 160 ~ 200 ℃. It takes 2 hours to achieve the purpose of sterilization; when the temperature is 121℃, the sterilization time is only 15-20 minutes.
(4) There are other sterilization methods such as lysozyme, nanometer, and radiation. But the most commonly used method is the filter filtration method for sterilization. The filter filters out the bacteria and microorganisms attached to the dust while filtering the dust particles.
Post time: Sep-16-2021