Autoclaves are crucial weapons in the fight against disease, and are responsible for destroying dangerous microbes and guaranteeing sterility and hygiene. In hospitals, kitchens, dentists and tattoo parlors, they halt the transmission of dangerous diseases, and are mandatory for many industries and applications.

Autoclaves are available in a range of sizes, from the small tabletop versions used by dentists and tattooists, to the industrial sized models found in large hospitals and kitchens. Despite the huge array of options and sizes on the market, they all operate upon the same basic principle, using superheated steam to neutralize and destroy pathogens.

As we are all aware, water boils at 212 degrees Fahrenheit (100 degrees centigrade), but this temperature is not sufficient for neutralizing many pathogens.  Some bacteria and fungal spores are resistant to heat, so a much higher temperature is needed for quick and efficient sterilization. Simple physics comes to the rescue, because water heated under pressure reaches a much higher temperature. The resulting superheated steam denatures microbes in a few minutes, rather than many hours.

Many dangerous bacteria survive at normal boiling points, and they are becoming a major challenge to the medical community. As an example, the ‘super bug,’ MRSA, which is largely antibiotic resistant, is a recurring issue in many hospitals. Autoclaves are on the frontline against this serious threat to health.

Autoclaves heat water under pressure, reaching a high enough temperature for thorough sterilization. The operating temperature needs to be at least 250 degrees Fahrenheit (121 degrees centigrade), but some strains of bacteria, fungal spores and rogue prions manage to survive past this point. With the rise of Creutzfeldt-Jakob Syndrome and related conditions, most modern autoclaves are designed to reach an operating temperature of 273 Degrees Fahrenheit (134 degrees Centigrade).

A good quality autoclave must extract as much air as possible from the sterilizing chamber, because hot air is an extremely poor sterilizing medium. Autoclaves all have a sealable pressure chamber, into which superheated steam is injected and air extracted.

Traditional models rely upon gravity to displace the air from the sterilizing chamber. Steam is much lighter than air and, as it is injected into the pressure chamber, it forces air downwards, trapping it in a sink. A system of valves and taps bleed out this excess air, allowing the steam to sterilize the contents of the chamber.

These autoclaves are the cheapest option and they are very easy to use. As a result, they are common in kitchens and manicurists, where they are more than adequate. However, for sterilizing porous or wrapped materials, displacement autoclaves are not efficient enough. Hot air may be trapped inside, allowing pockets of microbes and other pathogens to evade the sterilization cycle.

For complex sterilization, or in areas where complete sterility is necessary, a vacuum autoclave is the superior choice. Vacuum autoclaves evacuate the air, with a vacuum, and steam is then injected into the chamber. This allows the steam to penetrate porous materials, wiping out any pockets of pathogens in hard-to-reach areas.

After this steam sterilization stage, the pump again evacuates the chamber, drying the autoclave contents thoroughly. This added stage prevents germs and prions being retransmitted by trapped moisture. Vacuum autoclaves are the preferred option in medical institutions, as a more effective alternative to the simpler displacement autoclaves.

Many hospitals use disposable medical equipment, to prevent the transmission of CJD variants, but the contaminated waste is still autoclaved before landfill. Autoclaving is a more environmentally friendly method than traditional incineration, which ejects toxic gases into the atmosphere.

Better quality autoclaves incorporate temperature and pressure gauges, to monitor the process and ensure that the sterilization process is thorough. However, malfunction is always a possibility, and autoclave operators use a few tricks as a back up check, ensuring that there are no doubts.

Many autoclave users place items into special autoclave bags. These incorporate a colored arrow that only changes color when the correct temperature and exposure time are fulfilled. Autoclave tape, which turns dark when sterilization is complete, is another option. For critical applications, thermo-resistant bacteria, and alloys with a melting point of 250 degrees Fahrenheit are used to indicate a successful cycle.

Autoclaves are a frontline tool in the battle against pathogens, including prions and antibiotic resistant bacteria. Tattoo parlors, manicurists, dental surgeries, hospitals and a wide range of other industries rely upon autoclaves to guarantee sterility and prevent the outbreak of disease.