Difference Between Autoclave and Dry Heat Sterilizer (With Table)

Sterilization is the process of eradication or killing of all types of microbial life forms like bacterial spores, which are highly resistant, and viruses from the surface of instruments. For that process, heat, steam, pressure, etc., are used in machines like autoclave and heat sterilizers. Both perform the same work, but there are quite a few differences between the two that make them stand apart.

Autoclave vs Dry Heat Sterilizer

The difference between autoclave and heat sterilizer is that Autoclave uses temperature and pressure for the process of the sterilization, and the latter uses heat to do the same. Apart from that, an autoclave is quite fast and takes less time to get the process completed, while a heat sterilizer is slow and takes more time to complete the same process.

An autoclave is kind of a pressure chamber, vessel-shaped looking which uses high pressure and temperature to complete the sterilization task of equipment. It is the most effective, oldest, and the most common method to perform sterilization. It destroys both pathogenic and non-pathogenic types of microorganisms along with spores and viruses.

Dry Heat sterilizer performs sterilization process using an oven in which heat is maintained to kill the microorganisms. The period to complete the task depends solely on the temperature that is maintained in the heat sterilizers. It is another popular method to perform the sterilization process. It is only used for items that get affected or damaged by moist heat.

Comparison Table Between Autoclave and Dry Heat Sterilizer

Parameters of comparisonAutoclaveDry Heat sterilizer
DefinitionIt is a machine that sterilizes instruments using time, temperature, and pressure to kill any microbial on them.It is an oven that uses time and heat to sterilize to kill any microbial life.
CostAn Autoclave is comparatively more expensive.Heat sterilizers are less expensive.
RequirementThe Minimum temperature required is 121 °C or 250 °F with a pressure of 15 PSIG.At a temperature of 320 °F, it takes 2 hours, and with 340 °F it takes only an hour for sterilization.
Time takenIt takes less time to complete the process.It takes more time to complete the process.
Initial costingInitial price and ownership cost are relatively high.Initial price and ownership cost are relatively low.

What is Autoclave?

Autoclave, as discussed above, is a sterilizing machine that consists of a pressure chamber and a vessel that kills microorganisms alongside viruses and spores. Autoclaves are also commonly known as steam sterilizers. It is mostly used to sterilize dental or hospital equipment or supplies. Autoclaves are available in different sizes and all types. It uses temperature and pressure to perform sterilization.

Autoclaving is the oldest and most entrusted method of sterilization as it’s free from any environmental hazards. Despite the arrival of new methods and machines, Autoclave remains on top of preference when it comes to sterilization in hospitals and laboratories. The items or equipment are first placed in an autoclave pressure vessel and then heated to an appropriate temperature in a stipulated time required to destroy the protein structure of the microorganisms, which eventually kills them. The moisture in steam provides the required heat to the equipment or items placed for sterilization.

Three things are very important in the Autoclave for sterilization to be successful, namely, time, temperature, and pressure quality. The quality steam for quintessential sterilization consists of 97% vapor steam and 3% moisture (liquid water). The steam is called superheated, which is very dry and is efficient in transferring heat to the pressure vessel.

What is Dry Heat Sterilizer?

Heat sterilizer machines are an oven-like structure that uses heat to sterilize the equipment or items which are damaged by moisture. It uses hot air to perform the task. Heat sterilizers use the phenomenon of conduction to complete the process of sterilization. The superficial layer of the item placed in the sterilizer absorbs heat and transfers it to the inner layers and so on until the whole item is heated, eventually leading to the achievement of the idle temperature required for sterilization.

There are two types of heat sterilizers, namely, dry heat sterilizer and moist heat sterilizer. One thing that should be made sure while using dry heat sterilizers is that the equipment or item to be placed in the sterilizer for sterilization should be completely dry with no trace of water or any liquid on it as that may interfere in the sterilizing process and will deteriorate the quality or damage the item.

In moist heat sterilizers, the moisture content speeds up the heat transfer process and thus, enhances the entire sterilization process. The high-velocity hot air mechanism is more efficient in the heat sterilizers as it uses detribalized hot air, which is made to force through the jet curtain at a high rate.

Main Differences Between Autoclave and Dry Heat Sterilizer

  1. Autoclaves are sterilizing appliance that uses temperature, pressure and time to kill any stance of microbial life from the instruments whereas on the other hand dry heat sterilizers are the oven-like appliances that use temperature and time to eradicate the microbial life from the surface of instruments.
  2. Autoclaves are more costly in comparison to heat sterilizers.
  3. The initial purchase cost and the ownership cost of autoclaves are comparatively higher than those of a heat sterilizer. Heat sterilizer initial purchase and ownership cost are less than of a steam autoclave.
  4. In autoclaves, a minimum of 121 °C or in other terms, 250 °F temperature is required to be maintained along with a minimum steam pressure of 15 PSIG for 15 minutes, whereas in heat sterilizers, for proper sterilization it requires 320 °F, which takes about two hours or else 340 °F to achieve the same at 1 hour.
  5. Autoclaves are capable of performing sterilization processes on several different materials simultaneously in the minimum time and as fast as possible, whereas heat sterilizers are comparatively slow in performing the sterilization process and thus, takes a longer period to complete the task fully.

Conclusion

Despite the fact that both autoclaves and heat sterilizers are used to perform the same activity of sterilization, there are a few advantages in both two which makes them different from one another in many possible ways. The maintenance cost of heat sterilizers is low because of their simple design and are easy to operate. In spite of the highlighted difference, the operation cost for both is mostly the same. 

Autoclaves perform sterilization on all types of equipment that can bear heat and moisture. On the other hand, dry heat sterilizers are used to sterilize those items which can’t accept moisture or which are impenetrable by steam.

References

  1. https://www.sciencedirect.com/science/article/pii/S0377840107005445
  2. https://journals.sagepub.com/doi/abs/10.1177/002199839202600106

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