Some years ago I made a vacuum distillation of ethanol water mixture in a lab column and had no this experience. To do vacuum distillation you start evacuating the system, so, unless some leaks occur, there is no problem. So you have to check leaking in the system before its operation.

Also some distillates are made by vacuum. Petroleum is also vacuum distillates in a lab.

No one uses fire as a heat medium only fire proof electric heating. 

But for safety reason I I think that you can consult some distillation column manufacturer to know the necessity of special safety system for your process.   

See a Patent document on "Reduced pressure distillation of an alcoholic mixture" at following threads -

http://www.freepatentsonline.com/7780999.html

https://www.google.com/patents/US7780999

Thank you Silas, for sharing your experience with me. In fact, following your advice, I have  consulted a distillation column manufacturer, and he has already send-me some advices. My problem is not a lab distillation, but an industrial-scale distillation.

Tahnk you Yogesh, for sending-me this interesting patent. The method they use, is putting a portion of the fluid alcoholic mixture below 0ºC. With this procedure, they avoid most of the safety problems caused by the distilation of the alcoholic mixture under reduced pressure.