What is the difference between Oven and Dry heat Sterilizer (DHS) used in pharmaceutical industries?

In pharmaceutical companies, both Oven and DHS plays very important role. Specially in microbiology Oven is used as an alternative of dry heat sterilizer (DHS) as both can maintain very high temperature inside the chamber which is required for depyrogenation (removal of endotoxin at high temperature). 

Hot Air Oven

But what is the difference between Oven and Dry heat sterilizer (DHS)?

In Oven surrounding air is thrown into the chamber and hot air circulated inside the chamber. But in DHS filtered air is coming through the HEPA filter and hot air circulated inside the chamber. HEPA filter is not available in Oven.

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