Hi craz4cakes.
I jump in as I spoke with Reverie recently and I know that Sarah is unavailable for a few days
Everything off-gasses some levels of VOCs, even fruit off-gass. The only reliable way to assess the “safety” of different materials in more general terms is based on lab tests and the certifications they have for harmful substances and VOCs so that you have some assurance than the VOCs are below the testing limits for the certification (see post #2 here for more information about some of the more reliable “safety” certifications). If the materials in a mattress or the mattress itself have a reliable “safety” certification then for most people they would certainly be “safe enough”, regardless of the type of material.
All the latex you are likely to encounter (either Dunlop or Talalay that is made with either natural or synthetic rubber or a blend of both) will have a reliable certification such as Oeko-Tex, Eco-Institut, Greenguard Gold or C2C and based on actual testing I would consider any type or blend of latex to be a very “safe” material in terms of harmful substances and VOC’s (off-gassing) abd their FR barrier tends to be quite innocuous.
Phoenix