Laboratory autoclaves?

Question

I would like to know more about the laboratory autoclaves.
What it is & how it works
What can & what can’t be autoclaved
How to use an autoclave properly & safely
Causes of autoclave failure
How to ensure that the autoclave is working properly

Answer 1

An autoclave is a pressurized device designed to heat aqueous solutions above their boiling point. It was invented by Charles Chamberland in 1879.

Introduction---
Under ordinary circumstances, heating water above the boiling point in an open vessel is impossible. Whenever the temperature reaches 100° C, water ceases warming. This is due to the extensive evaporation that occurs during boiling. The evaporation process itself requires all the heat, thus preventing the temperature of the water from increasing. If water is boiled long enough, it turns to vapor.

When water, however, is heated in a sealed vessel (such as an autoclave), it is possible to increase its boiling point. When the temperature reaches approximately 90° C, extensive evaporation takes place. Water vapor, being a gas by nature, creates excessive pressure within the vessel. As vapor pressure in the vessel reaches the value that corresponds to the temperature, evaporation stops. Since evaporation stops, not all the water turns into vapor. The higher the temperature, the higher the pressure of the vapor. The heat generated under pressure is called latent heat and has more penetrative power to squeeze through bacteria and even their dormant, heat-resistant form — the spores. This works well on solid objects; when autoclaving hollow objects, however, (hypodermic needles, tools, etc.), it is important to ensure that all of the trapped air inside the hollow compartments is vacuumed out. Otherwise, it will act as thermal insulation for the bacteria inside.

Simple autoclaves use a single pulse pre-vacuum, while a modern day autoclave has fractioned pre-vacuum that pulls the air out in several stages to achieve 100% steam penetration in the sterilization process.
Autoclaves are widely used in medicine, dentistry and metallurgy.

Autoclave quality assurance---
There are physical, chemical and biological indicators that can be used to ensure an autoclave reached the correct temperature for the correct amount of time.

Chemical indicators can be found on medical packaging and autoclave tape, and these change color once the correct conditions have been met. This indicates that the object inside the package, or under the tape, has been autoclaved sufficiently.

Biological indicators include Attest devices. These contain spores of a heat resistant bacterium Bacillus stearothermophillus. If the autoclave did not reach the right temperature, the spores will germinate, and their metabolism will change the colour of a pH-sensitive chemical.

Physical indicators often consist of an alloy designed to melt only after being subjected to 121 °C for 15 minutes. If the metal has melted, the change will be visible.

As well as these separate indicators, autoclaves have temperature and pressure gauges visible from the outside.

There are certain plastics that can withstand repeated temperature cycling greater than the 121 degrees Celsius required for this process. PFA is an example.

Computer-controlled autoclaves use an F0 (F-naught) value to control the sterilization cycle. F0 values are set as the number of minutes of equivalent sterilization at 121 °C (e.g: F0 = 15 min.). Since exact temperature control is difficult, the temperature is monitored, and the sterilization time adjusted accordingly.

Loading an autoclave---
(These directions are for a typical front loading autoclave, but apply to most autoclaves)

1. Clean and inspect the autoclave regularly. Check the autoclave door gasket, drum, and steam return filter for corroded pipes.
2. Use distilled De-ionized water, or other clean neutral pH water.
3. Autoclave dissimilar metals (aluminum, brass, steel) in different loads as electroplating may occur which will permanently stain the tool.
4. Use towels to separate instruments and absorb moisture if needed.
5. Autoclave hinged instruments in the non locked open position, if locked the tool may become damaged (usually at the hinge).
6. No sharp instruments should be allowed to touch other instruments.
7. Do not over pack the autoclave, steam should be able to get to all sides of all pouches.

Answer 2

Lab autocalaves are basically sterilizers for any kind of sterling silver or metal equipment normally used by doctors or nail care places. It sterilizes with extreme heat and drying methods. Basically anything metal can be used in the autoclave. Best bet is to follow the autoclave's directions that came with the machine. All have different settings and directives. Lack of power, low water in water storage for the water vapor. Again read the instructions that come with the machine or get on the internet and look for the type of machine you have and see what you can find out that way.

Answer 3

To clean them of possible contanimation from viruses and bacteria.