Why can't it be replaced? Because it is not safe. The bottom of the electric drying oven is provided with a supplementary hole for fresh air, and the top of the studio has a ventilation adjustment port. The heated gas can be naturally discharged from the ventilation adjustment port. The studio is an unclosed container, so it only bears Very small gas pressure difference. The working room of the vacuum drying oven is subject to a negative atmospheric pressure, so the sealing is quite good. If heated without vacuum, the expanding gas in the working room may be generated due to the expansion of the glass or container of the observation window. Explosion accident. (Contributed by Beijing Yashilin Technology Department) Handrail System,Handrail Systems With Chrome Tube,Crossbar Holder for Handrail,Rotary Connector For Handrail System JOKER UNO LIMITED , https://www.jokeruno.com