The term “Autoclave” is taken from Greek word “auto” which means “self“, and a Latin word “clavis” which means “key“. Therefore autoclave means a ‘self-locking’ device.
The autoclave is the machine that is used to sterilize the equipment’s and supplies under high-pressure of 121 °Celsius or 250 ° Fahrenheit for about 15 minutes and the process is commonly known as ‘autoclaving’. This process of autoclaving is widely used in the field of medical, microbiology, dentistry, veterinary science, in testing laboratories.
To begin with, it is important to understand the meaning the word ‘ sterilization‘ which is directly related to the the whole process of autoclaving. Sterilization simply means to make available something (instruments) free from viable microorganisms, by the use of dry heat or steam.
Autoclaves or steam sterilizers works by using the steam under pressure with the aim of killing the harmful microorganisms like fungi, bacteria, spores, and viruses that are present on the equipment’s or instruments and are been placed in the space provided in the pressure vessel.
The supplies or equipment’s are heated under the appropriate temperature and for certain time limits to make the sterilize. This steam of the pressure vessel efficiently works by transferring heat to the items and thereby demolishing the protein structure of the growing microorganisms.
Invention of The Autoclave Machine
The autoclave machine that we are using today are far more advanced than what was being invented in the year 1969 by the French-born physicist ‘Denis Papin‘. At that time, it was a pressure cooker (a prototype of a steam digester or autoclave). Later on, in the year 1879 a French microbiologist ‘Charles Chamerland‘ created an advanced version of that machine, which is known as autoclave and is broadly used for medical appliances.
After few years, that is in the 1881 the researcher ‘Robert Koch‘ came up with the phenomenon of sterilization and disinfecting that can be done with hot and steam air. He proved by demonstrating the high potential of moist heat ( steam) in killing the microorganisms as compared to the dry heat. Finally, in the year the 1933 the advanced autoclave technology came into existence with the regulator that controls the temperature and time needed to maintained for that particular item.
Later on, with the up surging time the new autoclaves machines with more advances were introduced and therefore helped the science and technology to evoke in far more better way.
Working of an Autoclave
As discussed earlier, that autoclaves are more commonly used n healthcare sector with the purpose of sterilizing the medical equipment’s or devices. There is a chamber in a machine (pressure vessel) where the items are needed to be put for the process of sterilization and after that proper timing and temperature is been set. Therefore, whole procedure of steam sterilization depends on three critical factors in an autoclave: temperature, time, and the quality of steam.
Thus, this process of sterilization undergoes three phases to meet the requirements: Conditioning Phase, Exposure Phase and Exhaust Phase.
Conditioning Phase (C): The air present in the chamber suppress the process of sterilization, and therefore it becomes priority to remove the air from the chamber in the first phase of sterilization cycle, this process of removal of air is known as conditioning.
In case of the Gravity-type sterilizers, the steam is used to replace the air present in the chamber and forcing the air to drain down from the sterilizer drain. Whereas, in the dynamic air removal-type steam sterilizers, the air is evacuated from the chamber by using a vacuum system or another options such as pressure pulses or steam flushes can also be used.
Exposure Phase (S): After the air is removed from the chamber, now the sterilizer drain is closed and thus allowing the steam to enter continuously into the chamber, with the simultaneously increase in the temperature and pressure that was predetermined. Therefore, this phase is known as exposure phase as the items present in the chamber are ready to get exposed to the steam and get sterilized for the fixed amount of time and pressure.
Exposure phase may vary with the shape, size, weight and density of the material that is needed to be sterilized, in addition ot other factors. Therefore, exposure phase is only a part of the whole sterilization cycle which is been developed by scientific testing.
Exhaust Phase (E): In the final phase of the whole cycle, i.e. exhaust phase, the steam is removed by opening the sterilizer drain, and later on depressurizing the vessel and thus the equipment’s are ready to dry in the load.
Important points to be notice is, the quality steam should be maintained through out the process to make it a successful one. The reason is the ratio of steam and liquid water that is recommended as it should be of 97% of steam (vapor) and 3% contribution of moisture (liquid water). If the moisture is less than 3% the steam is considered as the dry heat or superheated and this type of heat is too dry for effective steam sterilization and therefore, the this is the preferable ratio to be considered.
Secondly, the recommended temperature range of an Autoclave is 250 ° F (121° C), 270 °F (132 °C) or 275 °F ( 135 °C). Studies have shown that these are the required temperature to kill the microorganisms present in the items that are to be sterilized under given time and pressure.
The bottom line is as the autoclaving process undergoes through the high temperature and pressure, therefore, items made of paper and plastics cannot be used for the sterilization purpose. However, forceps, scissors, scalpels, glassware’s, and other metal items can be sterilized, in order to get rid of microorganisms.