Who said anything about preservation, if the shockwave is strong enough it will knock out the fire, which was the goal in the first place.
Also Darkvision , this could be effective eventhough it might be destructive, the video's you posted do nothing to reinforce any statement you made.
Not saying it is a good idea, but this is theory.
Thats like saying e=mc^5(hippopotamus*rhombus) is a valid theory. Only if you understand nothing of the subject at hand can that look like a remotely good idea or to have any ability to work. Really i shouldnt even explain any of this further, and simply tell you to go take a fire safety class(most local fire stations do them at varying times) or to read up online about fires. Though this is one of the few instances where a class is better because they will often demonstrate the procedures AND let you do them as well(at least the good ones do). Fire safety can not only save your life, but the lives of those around you. Think of it as learning emergency first aid, except this can save hundreds of lives at a time instead of just one. It is seriously that important. Instead of talking cut and dry about things like firewatches and why they are necessary(and hence why the whole "knock out the flames for two seconds" doesnt work), i will instead talk about a few other things that are VERY much related.
First off lets look at your good ol' charcoal grill. These coals are NOT on fire, they are smoldering. They are giving off enough heat to cook food...and yes set fire to it or anything else flammable close enough to it. When your shock wave knocks out the flames, because of the latent heat in the embers and coals that are now EVERYWHERE, it will do one of two things: set fire to new things or burn the things it already was. When you deprive a fire of oxygen its not for half a second and then your done, you have to CONTINUE to do so until it has cooled enough that it cant reignite or ignite something else. Again with that example after you finish grilling and put the lid on and close the vents you should STILL keep the grill in sight for at LEAST an hour to make sure something doesnt go wrong. because even an hour later without oxygen they are hot enough if knocked out of the grill to likely start a fire.
That shockwave is carrying with it embers metal and i am sure all sorts of wood that it can put through you. the fire is the least of your worries because shrapnel comes FIRST. After that you will be too dead to give a shit about a piddly ole fire everywhere. Want to see how effective shock waves are at putting out Class A/B/D fires? Here is something that to this day every US Navy sailor is required to watch in bootcamp. The story of the USS Forrestal.
https://www.youtube.com/watch?v=U6NnfRT_OZAOh and i wasnt joking about the Class C thing earlier, it would technically when the electrical connection ceased from the shrapnel STOP being a Class C fire, it would then be most likely a Class A.
