The box arrived earlier than expected and I was able to let the mattress air out for a few days before sleeping on it. While there is a chemical smell when first opened (with the help of an OZONE air cleaner), the smell was gone in about four hours. I had my first sleep on this mattress last night.  Wow, I actually at one time found myself sleeping on my back something that usually causes a great deal of discomfort. Arthritis in my knees make most mattresses uncomfortable but, this mattress is wonderful.