Hi momof3,
American made polyurethane foam (such as the reflex foam they use in the quilting and the foam they use in their base foam) is generally CertiPur certified which means that it has been tested for offgassing. Latex (such as the talalay latex used in their customizable comfort layer) is OekoTex certified which also means that offgassing is also not an issue.
While polyfoam has more harmful chemicals in it than blended latex and some will even prefer all natural latex and other natural fibers such as wool in their mattress over any polyurethane at all … this is really a matter of each person (or parent) deciding for themselves “how safe is safe” and there are many conflicting opinons on this all the way from “no synthetic materials including polyfoam of any kind” all the way to “if it is certified as safe then I am fine with it”.
The type of foam that generally has the most offgassing issues is memory foam and I would always make sure that any memory foam used in a mattress was either American made or CertiPur certified (some Chinese manufacturers have the same CertiPur certification as most American manufacturers). I would also not use memory foam anyway for a young child that was still growing not only because of any potential offgassing issues but because memory foam itself is not a great choice for a child in terms of maintaining the best alignment and for a baby or infant it should never be used at all IMO. There is more information about mattresses and children in the links in post #2 here.
You can either let them know in your response to the email you will receive after an order which asks you to choose the firmness of the comfort layer or better yet you can call them on the phone and talk with them about the firmness level that may be best and take advantage of their guidance. Their phone number (and you will be talking with Chuck) is listed on the bottom of their Amazon shipping page so is a little hard to find. It’s 1-877-955-5503.
Phoenix