The first thing you will do when you get your Idle mattress is bring it to the room you will open it in. You do not want to unroll it in another room. Once you are ready to open it you can use the cutter some brands provide, if not use a scissors and be careful not to cut the fabric.
As it starts opening it will expand quickly and you will only notice a slight “new mattress smell”. The Idle mattress is made in the USA so it is not roll packed very long, which helps with minimize off gassing.
“Off Gassing” for me is tricky because no matter what brand you are looking at they are going to have a smell. “Natural” or Organic” mattresses often times have the strongest smell, even though people associate them with no off gassing. A smell is normal and no matter what brand you buy is going to have some kind of new smell.
In most cases the smell will be gone within 12-36 hours or very faint. I always recommend using a mattress protector so once the mattress airs out use a protector and sheets and at that point you should not experience much smell at all.