How long does it take low density polyurethane to decompose?

Answer 1

It depends on what type of foam it is and where it is: whether it's exposed to head, humidity, open air, etc. I carried a polyurethane mattress out of an old person's spare bedroom in 2010. It had been purchased in the 1960s and had turned mostly to a granular, sand-like material. Thankfully it was enclosed within a zipped mattress cover or it would have been a huge mess. I have also seen the polyurethane within a 20-year-old house door granulate and pour out the bottom, likely assisted by burrowing insects.