Outgassing of the inner core materials. Most fire retardant is done with Boric Acid, which is largely odorless.

There are ways to get custom futons that do not smell, but they will not be inexpensive.

I was inclined to think it was something offgassing, but... offgassing is supposed to decrease over time. I have a %+ year-old futon which smells every bit as terrible as it did the day I got it. Just like every other futon I have been near , regardless of their age.

In any event, if it is simply a continuous outgassing of core material, then... what is the core material?

Thanks!

just another reason to NEVER get a futon!