The instructions say to let the mattress topper sit out for 24-48 hours to air out. We left it out for over a week before putting it on our bed. Even with all that time the smell is really strong. It's giving my husband headaches. It's a super comfortable topper. It's made a world of difference on my old, crappy, mattress. I LOVE sleeping on it but I'm worried we won't be able to handle the smell for much longer.