It is always a danger to health working in a microbiology or pathology lab. In such laboratories where lots of work goes on with bacteria and virus, or possibly infected materials, the need for sterilization is paramount. The slightest chance of contamination from a ‘dirty’ apparatus can shut down a whole lab, and ‒ let’s hope not ‒ get someone deadly sick. This is where an autoclave comes in very handy.
Bacteria and viruses and living or semi-living things ‒ and as such, they can live within very specific boundaries only ‒ in specific environments. Unlike the glass beaker that held some bacteria culture, they won’t survive at high temperatures and pressure. And that is the environment you can create within an Autoclave ‒ very unfriendly to any kind of microorganism.
According to Wikipedia, An autoclave is “a machine used to carry out industrial and scientific processes requiring elevated temperature and pressure in relation to ambient pressure and/or temperature.” So, what does that mean for a laboratory?
A laboratory that deals with microbes have a lot of glassware and apparatus that come in contact with dangerous bacteria and viruses on a regular basis. And cleaning them with just soap and water is not enough ‒ most microbes can persist well after even a good thorough cleaning. To really make sure all the contaminants are definitely killed, you have to subject them to heat ‒ and pressure.
An autoclave does just that. Think of it as a pressure cooker for lab apparatus. It basically ‘cooks’ various heat-resistant glassware and apparatus with extremely hot air or steam under high pressure for a good amount of time. The heat and pressure make sure all living or semi-living organisms (like viruses) die and disintegrate into harmless waste compounds.
Also called a steam sterilizer, autoclaves are basically machines that create an artificial environment of high heat and pressure. Think of an autoclave like a high-tech pressure cooker ‒ inside which you cook your flasks, beakers, tongs, dissection tools, and such stuff ‒ that creates an extremely inhospitable environment for life. Kind of like on a very big planet very close to a star. An autoclave does this through the following structure.
Video courtesy: Forsyth Tech CTL (Original video here)
The autoclave, funny enough, works with the same process as we use in our kitchens every day to cook hard meat. When proteins get heated above the boiling point of water, they coagulate into some biologically inert substance. But how do you subject something to high temperatures easily?
By boiling water under pressure. The relationship of boiling point with pressure is that the more pressure you apply on a liquid, the higher its boiling point spikes. Water is the most commonly accessible liquid on earth, and it boils at 100 degrees centigrade normally. But put more pressure on it and it gets hotter and hotter, but won’t boil. At 15 psi, you have to turn up the heat up to 125 degrees before you see the water boil. And this steam, of course, carries a lot more heat than water vapor at normal pressure.
When this superheated steam of 125-degree temperature hits any living organism ‒ i.e. a microbe clinging to the walls of a beaker, in present discussion ‒ it transfers all that heat to that microbe’s body. Now a curious thing happens. Much of any living organism is made of some kind of protein, and protein behaves badly in contact with heat. It loses its definitive structure that gives it the qualities of a protein, and gets condensed into some other shape. In effect, the “living” part of a living organism gets pounded out. And that’s how you kill germs, properly!
Though we should note here that some particularly determined and enduring forms of life, like endospores and archaebacteria, can still survive this level of torture. For them, a whole different kind of thing is needed ‒ we’ll talk about it later. Generally, you don’t have these issues with standard lab work at microbiology labs or medical labs.
Autoclaves are a very common lab machine ‒ you can find one in almost any microbiology or medical laboratory. These labs use the machine for sterilizing their glassware and steel surgical apparatus. A tattoo or body piercing parlor won’t really be safe without an autoclave, either.
Other than sterilizing things, you can also process medical and biological waste in an autoclave before disposing of it to make sure the environment doesn’t get contaminated. A specific decontamination system exists that cures liquid waste of all contaminants.
Laboratories use smaller, vertical autoclaves; while hospitals and pathology labs may use bigger models that look more like a bank vault. Industrial usage of autoclaving sees even bigger chambers vulcanizing rubber and cooking composite materials. Some autoclaves get as big as holding whole airplane body parts inside ‒ making composite body parts.
You can grow some special crystals at high temperatures and high pressures only ‒ such as the artificial quartz they use in electronics. Parachutes and similar stuff are packed using the same technology as well, but I wonder if that machine can be called an autoclave or not.
In general, most common autoclaves are run at 121 degrees centigrade for half an hour. The step-by-step instructions to run an autoclave are as follows.
As with most lab instruments, autoclaves come in many different shapes and sizes and structures. As mentioned above, they can be small pressure cookers to huge rooms holding whole vehicle bodies. Here are the most common types of autoclaves and their uses.
Also called pressure cooker autoclaves, these are the smallest ones out there, literally no bigger than a large pressure cooker. Some even come with an internal heater ‒ you have to mount them on some kind of hot plate or stove. As the name suggests, they are little more than just basic pressure cookers. It’s used in small labs for regular work, like in the pathology departments of small clinics.
The most common type, you can see this vertical autoclave in most microbiology and medical college labs. They have a steam generator separate from the pressure chamber. These are comparatively cheaper than most other types of autoclaves, being so common and easy to make.
A completely separate steam generator feeds the main body of the autoclave in this system, which is faster than most others since ready-made steam is available from before. This way, you can do multiple sterilization operations in quick succession.
This one has both a steam generator and a vacuum generator. The vacuum generator first sucks out the inner air before the steam starts rushing in. This is a great way to sterilize anything since there is no chance of outside air assisting life growth. So, if you need great accuracy of autoclave sterilization ‒ use an S-type one.
Generally all autoclaves you’ll see in use will work in one of the above ways, but they can differ a lot in shape and size. For example, the most common type of autoclaves are the vertical autoclaves but there are horizontal ones too. Some are compact and look as if a microwave oven and a cabinet-size vault fell in love and made a baby.
Some are large floor standing machines into which you can push in an entire trolly full of material to be cleaned. Some are lab workhorses suitable for frequent repetitive sterilization; some delicate ones again require a lot of maintenance or cleanup between usage. And all of them have some or other specific scenarios to cover. The laboratory equipment world is so awesome and complex, when you think of it!
External image courtesy: freepik
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