Hi malmzz,
The only reliable way to 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 that 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 has a reliable “safety” certification then for most people they would certainly be “safe enough” … regardless of the type of material or the name of the manufacturer on the label.
I’m not clear about the basis for your concerns about steel innersprings but there are no harmful substances or VOC’s in steel that would be a reason for concern and a steel innerspring would certainly be a safe component and all the materials and components in the Natural Escape would be a high quality and “safe” choice.
Phoenix