Has anyone besides Kevin ever seen the type of flex pipe as described below?
Nope! Not yet. 
But I don’t do 10 inspections a week. 
Have Mike find even on case where fire was blamed on the hood duct ?
More of a concern is lack of ducting in basement units that need to exhaust and those that terminate in walls or attics
One more note is to stick your hand up in the cabinet and you can still feel air at almost all as they are never sealed perfectly.
Yes, I installed them every single darn day for about 6 years.
Now for all you code inspectors here is an except from one manufacturer…
Only use ductwork constructed of materials deemed acceptable by state,
municipal and local codes.
Notice they themselves do not state not to use flex.
I haven’t either, maybe I need to start looking closer. 
Yeah …we all know how good Sears is…not installing anti-tip brackets cost them $500 million. I trust them completely!!!
Corrugated is wrong. It says so in the code books (yeah I know we don’t do code inspections yet ALL of our information comes from them). If you choose to comment on it or not is a business each and every inspector needs to make at the time of inspection.
My outlook. Tell them it is wrong and move on. If a problem occurs I told them about it. If nothing happens no harm no foul but I still told them about it.
Do what you will
So prove me even one fire started by wrong type vent on a microhood.
For a flame to get that hot it is already a major fire and it will be contained inside the metal flex.
Anyone claiming that a flex vent (metal or metal foil) is a fire hazard is talking out the side of their mouth with no knowledge.
What is the temp inside a hood vent on average?
Do you same pretend safety experts also inspect for one inch clearance from framing?
I think not!!!
I should have taken a picture of the last one. The grease in a residential fan is all in the filter that they haven’t cleaned or replaced in 5 years.
And Bob is right, if the fire jumps 24" up in the fan, you got a problem.:mrgreen:
Although, I am not a strong advocate on any flex duct, I don’t think I would get to worried on it’s usage for a range hood exhaust.
The picture that was posted looks more unprofessional more than anything else.
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Which one is a safety hazard?
Silly me as I actually inspect and photograph all kitchen appliances.
The grease covered fan with no filter and the oversized bulb used in the fan light.
Very interesting feedback and comments on this subject. For the most part I think it has been productive and shed some new light for many.
John I think they road that dead horse over the cliff 4 pages of post over a flex duct:shock::shock::roll: