Interesting question. I am a Certified Safety Professional and have worked in commercial kitchens in a past working life, but I must say I've never investigated this situation. Without seeing your setup, let me have a stab at it.
Your extraction hood is the key here, is there sufficient draw to capture all the smoke, especially when you need to open the door while smoking? You may have to extend the hood to ensure the smoke rolling out the door is contained.
Does your exhaust hood have fire protection such as a sprinkler or dry chemical, the code will demand this?
Thermal heat or electrical safety shouldn't be an issue if wired properly.
If I understand your question, you are asking if exposure to the smoke will present an inhalation hazard. If your exhaust hood is doing it's job, exposure would be minimal. The only way to "prove" minimal exposure would be to have someone conduct air sampling to determine concentration levels. I have conducted all manners of air sampling over the years and feel confident saying that 2 X 4 hours per week would show very small exposure, but of course I'm not there so take that comment with caution.
The only other thing I can think of is that your hood will need a filtration system before the smoke enters the ductwork. Over time, the ductwork will develop a coating of tar unless filtered. If you have a commercial kitchen you are familiar with the types of filters available, clean them regularly.
Let me know if you have any other questions, and I will respond if I think of other issues. Good luck.
