Douglas,
I understand what you are saying. My point is obviously "beating a dead horse " but I think it is something we should consider. Your example of burnt twisted filters. The restaurant burnt to the ground but the stainless steel, baffle filters were ok.
I dont think filters can stop a fire, perhaps deter it a little, but those grease fires and not easily contained. Look at it this way, a fire burnt the duct, fan ,filter etc etc. That was not the filters fault it, was the owner who let grease accumulate in the system to a point where if fueled the fire all the way up to the roof.
Now baffle filters may misdirect the flames but they also allow a lot more vapors up into the duct. Look at some of the pics on this site. Horrible duct, but I bet the filters were still allowing the air thru. I vote for filters that get blocked up and dont allow air thru when they system needs a cleaning. A smoke filled kitchen is more of a motivation for cleaning than the possibility of the "AHJ" stopping in. If the eventually do, will they site the owner? Ahhhh, look at the pics. Looks like years of grease.
I have seen stainless steel , several layered mesh filters. They do a much better job of catching the grease. Unfortunately they keep it. But lets say that there is a fire on a system that has mesh filters and has been cleaned. The mesh filters with grease in them will add fuel to the fire. OK. But the system being in good condition the fire is kept at the filters cause there is nothing else to burn in the duct.
My motivation is to keep the restaurants system grease free. (Actually money is my motivation) I am all for something that keeps the cleanings on track. Mesh filters are just another potential motivation for cleanings.
Another small point, ever put baffle filters in a hood that was meant for mesh. Often the angle of the filters is such that rather than the grease flowing down the baffle, it drips back on to the cooking area. The angle is too great to allow the baffle filters to work properly.
