r/Firefighting • u/Educational-Cat-5807 • 3d ago
Ask A Firefighter Information on scorch marks
Did a training burn last night, and went back this morning to check out the damage and see if i could learn anything about post-fire investigation before we do the final burn later today. The box we built was about 10 feet long, 5 wide, and 4 tall. Half of it was a sealed compartment, the other half was closed in by 2 walls and a ceiling. I think I understand why the scorch marks formed like they did, but can anyone give me a in-depth explanation by looking at the burn patterns, and tell me more about the science of it? Videos and photos attached.
151
u/MystikclawSkydive 3d ago
Where black - was fire.
Where no black - no fire.
Lower on wall black - closer to where fire start.
Bottom of V black - most likely where fire start.
Many things can make all I wrote above wrong.
Undetermined.
25
u/TacticoolBreadstick Not a hosedragger 3d ago
This about sums it up. Trust me, I watched a fire inspection youtube video before posting this.
1
1
77
u/moseschicken 3d ago
I just finished my fire investigation chapter in Officer class. I can tell you, based on the scorch patterns, that a fire likely occured.
15
u/skimaskschizo Engine Trash 3d ago
You should obviously be able to tell what caused it by looking at scorch marks. My pyromancy skills helped.
4
u/Joshiewowa 3d ago
I'd say something hot caused it, but I don't have any formal education on the topic
25
17
u/byndrsn Retired 3d ago
a bird carried a smoldering cigarette...
replace with squirrel as necessary.
8
u/dinop4242 former and future FF 3d ago
depends on if it was an African or European swallow
3
1
3
13
u/Zyrian1954 3d ago
The flow of fire within a compartment is influenced by a number of factors, but primarily by the materials involved, the geometry of the space and the ventilation of the space. Fires have four distinct stages: incipient, growth, fully developed, and decay and the images identify (to me) a fire transitioning from incipient stage to growth stage.
Post ignition the incipient stage will see hot gases produced by the fire rise due to buoyancy, entraining the surrounding air, and a fire plume is formed. As the fire plume reaches the ceiling of the compartment, a hot gas/smoke layer in the upper part of the room develops and will create a flow away from the initial materials and towards any ventilation opening. Simply, a fire grows upwards until it cannot go higher due to a barrier (ie: the ceiling) and then it flows into any uninvolved area and specifically towards any opening where ventilation exists.
As seen in the images the damage is low at one end of the compartment and the further from that end of the compartment, the higher the damage is on the walls. The walls will be clear at the bottom, then progressively more heavily smoke stained and then eventually charred at the top as the hot gas/smoke layer forms and flows outwards from the fire plume within the compartment. The ceiling will have more damage as the hottest part of the gas/smoke layer is at the ceiling and generally floor damage is 1/3 of ceiling damage as the fire fully reaches its growth stage.
My explanation is pretty much generalized as only the worst fire investigators draw any conclusion from pictures and in order to provide a more specific explanation requires an onsite examination to determine exactly what factors influenced the fire growth and spread. I’m a Fire Protection Engineer and I worked as a fire investigator for 24 years for a government agency and then 5 years for a municipality before I retired.
•
u/SamanthaSissyWife 7h ago
Sounds like a three letter government agency AT First
Great explaination!
23
6
11
4
u/Rude_and_Crude84 20+ yrs career faller on the FG. 3d ago
You should look for an Intro to Fire Investigation Class for the First Responder. It'll teach you what you need/want to know. Then go from there.
Also, that can be somewhat explained in some fire behavior classes, depending on how in depth your instructor is.
3
u/4Bigdaddy73 3d ago
I’d love to tell you some of the jackass answers you got on this post were not indicative of the fire service as a whole, but then I’d be lying to you.
Keep your head up and keep learning! It really is a great career.
3
13
3
u/Nasty____nate 3d ago
Roll over. Super heated gases and fire rolled out of the burn room. https://www.youtube.com/watch?v=aV2bjCdqyTY
0
u/UnhappyCaterpillar41 2d ago
You don't need rollover to get those patterns, and that looks like mostly soot deposit and very light surface charring. You can easily get that just from the hot smoke, which came neatly out of the door around mid height with some nice bidirectional flow patterns.
It's pretty easy to tell that the far room was on fire and a lot of smoke vented into that corridor, but it's a pretty bog standard compartment fire with smoke traveling internally.
2
2
2
2
2
•
u/rogo725 18h ago
NFPA 921 chapter 5
Cool fresh air is rushing in on the lower side toward the fire, hot flammable gases spreading out when hitting a horizontal surface looking for the path of least resistance.
If you’re interested in fire investigation, come over to r/fireinvestigation. Also, get a copy of 921.
3
1
u/Dudebro120 3d ago
The Black marks on the boards on the sides and near the opening where the fire was are just due to the hot gases, extending from the fire and flowing across the ceiling the charring at the on back of the box near the top where the fire was is due to ventilation. I assume the top of that “fire box” is open.
1
u/bbmedic3195 3d ago
Inverted v pattern leading back to the most damage and or free burn shows where the fire usually started.
1
u/redfiretrucks 3d ago
You are seeing the evidence of the flow path from the high pressure area where the fire started to a lower pressure area where there was no fire. As the flow path gets further away from the area of origin, it diminishes in intensity and doesn't reach as low as it did closer to the fire. Without seeing the video we can't tell if there was a flame front or just superheated gases, but the black marks on the highest sections of the board give you an indicator of where the highest heat levels were.
If you look at the charring and alligator char pattern in the far room, that burn level was much closer to the floor and the damage was far more deep in the wood. That should generally demonstrate that the fire began in that room, and the damage in the wooden corridor is from the gases exiting a high pressure area and going to a lower pressure cooler area, which is the path more fire gases take.
1
u/NotGayRyan FF/ PM 2d ago
Fire burns up and out.
And from the look of the photos. It looks like there was a fire in that hole and it came up and put of that hole
291
u/Suicyco71 3d ago
Looks like there was a fire.