Hi suziQ,
As [email protected] mentioned … offgassing is really a matter of degree. While mattresses and many other household items and furniture will have some degree of offgassing over the long term (even fruits and vegetables have offgassing) … it’s generally below the levels that most people would consider to be harmful after a few days or in some cases a few weeks although there may be a few people that are more sensitive or have medical conditions such as MCS (multiple chemical sensitivities) that may be sensitive to levels of some VOC’s that most people would be fine with. Some of the information in post #3 here may be helpful.
There is higher and lower quality memory foam made in North America by many different manufacturers (not just the memory foam that is made by Tempurpedic) and there is also higher and lower quality memory foam made in China by many different manufacturers as well. It would depend on the specifics of the memory foam and how it was manufactured. Having said that … I think it would be fair to say that there is some some additional risk and uncertainty involved in buying a mattress that is made in China or other imported mattresses that may be subject to longer periods of compression during shipping and storage that can sometimes affect the durability and useful life of the mattress (see post #6 here).
Tempurpedic has changed their mattresses many times over the years and also added many new models so that they have a wider range of mattresses to attract a larger percentage of consumers or keep more of their customers that purchased their mattresses previously because they now have a great deal of competition that also make similar or better quality memory foam mattresses (and many that are lower quality as well) that sell for lower prices that they didn’t have when they were first introduced (see post #2 here). The changes weren’t about having less toxins in their mattresses.
Phoenix