The purpose of autoclaves

Autoclaves are commonly used pieces of laboratory, healthcare, or industrial equipment. The purpose of an autoclave is to thermally destroy microorganisms. These devices are used to sterilize and disinfect instruments, media, or biological waste. Autoclaves are essential when working in laboratories as they ensure that contamination is eradicated when using laboratory tools, or other materials.

The types of autoclaves

Autoclaves can look very different from each other – from small boxes found in places such as your local nail salon to huge pieces of equipment with double doors, more commonly found in industrial settings. But size and capacity are not the only differing factors when it comes to autoclaves. Another common way to categorize autoclaves is by their class. There are three classes:

• Class N – can be used for various objects (solids or porous material). These autoclaves are compact in size and are usually tabletop devices. Class N autoclaves usually reach a temperature of approximately 120-135℃. Because class N uses steam to push out the air, these autoclaves cannot guarantee 100% effectiveness.
• Class B – autoclaves use a vacuum pump to remove all of the air in the chamber. Because of this effective method, class B can offer the highest reliability available. The temperature of class B autoclaves usually reaches around 135℃.
• Class S – autoclaves fall in the middle between class B and class N in terms of performance. They have some advantages in comparison to class N. For example, they usually have a microprocessor, therefore are more reliable and precise. Contrary to class N autoclaves, class S has a drying mechanism, and thus instruments will not come out wet after sterilization. Although, class S has less performance capability than class B and is less suitable for complicated instruments.

Working principle of autoclaves

Autoclaves use moist heat for sterilizing objects. A vacuum pump is used to suck out the air in the chamber and furthermore the temperature in the chamber is raised. The hot steam inside the chamber then kills off all the microorganisms inside.

There are a few differences in how autoclaves work between different classes (N, B, S). For example, in class N autoclaves – air removal is executed by displacing gravity and using steam to push out the air. Class B autoclaves use a vacuum pump for the removal of air and are very effective. Class S autoclaves remove the air inside the chamber using a steam wall which is denser than air.

Other methods of sterilization

Sterilization can be simply explained as destroying microorganisms such as bacteria, viruses, fungi, etc. It can be reached in any way that would create unsurvivable conditions for microorganisms. Autoclaves essentially utilize thermal disinfection, meaning that the temperature is raised enough to kill off microbes. This is one of the most effective ways but it takes some time to reach this temperature and not all objects can be fitted in an autoclave.

Chemical disinfection is another great way to sterilize various objects. It is usually cheaper to use chemicals and can be performed fast. This method is great for the disinfection of surfaces. Yet, there are some limitations to chemical sterilization as well – not all materials can take chemical disinfection and it also might be less effective in some cases.

For fragile objects and air disinfection, UV rays can be used. This method is not intrusive and less harmful to delicate objects. Some of the drawbacks of this method are that it is less effective (only a direct UV light path is effective for microorganism destruction). UV rays are also very harmful to people, therefore special carefulness is required while using UV for sterilization in greater capacities.

All in all, each sterilization method is useful when dealing with unwanted microorganisms. On each occasion, one might consider different ways of disinfection. Yet, autoclaves are one of the most popular and effective ways of taking care of medical instruments and laboratory tools.