Hmm, that is not something that we've ever heard before. Here is our experience on this subject:

1) The time when you are most likely to experience powerful smells or off-gassing is when the mattress is new, not when it's old.

2) The term "off-gassing" is typically used in regards to petroleum-based foam. Latex used in mattresses can be "synthetic" (i.e. 100% petroleum-based), "natural blend" (a blend of natural and petroleum-based), or "all natural" (100% natural). Either of the first two types of latex could experience some off-gassing. However, if a mattress is made from 100% natural latex, it may still have a latex smell at first, but it wouldn't generally be considered "off-gassing" due to the lack of chemicals in the underlying material.

3) In general, latex (even synthetic latex) tends to off-gas less than ordinary polyurethane foam, and much less than denser poly foams like gel memory foam.

4) The amount of off-gassing is not uniform across all materials of a given type. Put another way, not all synthetic latex will off-gas the same amount, just as not all polyurethane foam off-gasses the same amount.

5) If off-gassing is a big concern for you, you should look for mattresses that have obtained certifications for their mattresses or the materials they use in them. Specifically, the following third party organizations certify mattresses and/or their components for low emission levels or the lack of harmful chemicals: Certi-PUR, Eco Institut, GREENGUARD, or OEKO-TEX. There are also a few more stringent certification bodies like GOLS and GOTS that take it even further, adding the requirements of organic raw materials and socially responsible production methods.

Hope that helps!

I concur, the more pure your mattress, the less off gassing that may occur, the company OMI boasts the purest mattress on the market and they have a guarantee to back it up. Good Luck and try to shop at a locally owned store!