Mattress Forum

Because of chemical-sensitivity issues, I am not all that thrilled at all about buying a mattress with polyurethane foam, or purchasing a foam component to build my "sleep system" - but for ergonomic reasons, I may have no choice (yes, I've tried the supposedly "healthier" latex - it didn't work out).  So I wanted to ask this forum - what properties should I look for in foam that would minimize my exposure to offgassing substances and toxic flame retardants?

Is it true that the softer (in ILD) the foam is, the more it offgasses - or is the opposite true?  What about densitity - how does increasing densitiy affect the amount of offgassing?  Are there certain types/brands of foam that are known to offgass less than others?  Does the amount of flame-retardant used in the foam vary with firmness-level and/or densitiy? 

While I'm at it - I might as well ask if anyone knows of any particular brand of mattress that has little-to-no offgassing?  Which would be the lesser of the evils as far as this is concerned?  (My budget is quite limited - I cannot spend more than $800 on this mattress.)

Thanks for any feedback...