Flame spread rating on walls is a touchy subject.

Your castle, once it's built.

Anything that is so flammable (Like polystyrene egg cartons), that holding a match to the bottom of it results in a sudden in total ignition, is simply taking a huge risk.

So a spark lights the room up and you end up a roman candle.

Normally a building code has a minimum rating of flat plywood, in fact that works for most small places of assembly. But it's what's put up after.

I did a fire investigation in a high school. A kid lit a huge foam bag of pieces of foam on fire. (The foam was a portable indoor high jump pit.) That caused a fire and the hallway and walls burned. One whole wing of the school was damaged and had to be shut down.

There were 3 factors. The foam burned instantly when a match was applied.
The energy in the foam used up most of the 02 and the heated lighter than air gases went up the corridor, found more 02 and lit up. Then the heat caused the paint to be a factor.

The paint was latex so it's not flammable said the school board architect. In a public meeting and I was there. He was such a knob to me in the past that I smiled that grin you get when someone is going to be publicly humiliated (deserved eh).

I got up to the mic and asked him, "Randy, now why would you say the paint is not flammable..."

"Oh, really, and where does the water go when the paint drys?"

"Really, and what's left Randy?"

"I just want to tell everyone that 40 layers of latex on the wall of a high school will burn quite a bit, and it's a main reason that the fire spread so quickly."

Fun.

Most polystyrene couches have more fuel in them that a vehicle, and one couch like that will total a whole house in less that 30 seconds. Keep it away from extension cords and plugs. Shoving a couch against a plug for 10 years is just not smart.

Smart people do smart things. My nephew is a 24 year old guitar guru. Just ask him. The local A&W hosted a drive in teenburger gets a buck donation to MS, and his group was playing. We pulled in and they were in this fairly small tent, 5 people, he was playing the heavy guitar, you know, the lead one. 80's music, I dunno, but I said to the wife, 'jackasses'.

My wife rarely responds to that, but I said it a second time as my niece passed me a golf umbrella and the band ran to safety. They put the band under the tent and the sound gear on a table of some sort 6 feet away, under no tent or umbrella. I opened the back of the car, unfolded a plastic tarp, and covered the 16 or so channel powered mixer. I never did kick out. I tried explaining to them that it's more important to cover the gear than the heavy singer. She was also a lead singer. And had the weight and the voice. Too bad the others, despite ear pieces, were flat all the time.

John Conley
Musica est vita