Visco-elastic foam is the only substance which can make a total imprint of your body, but then slowly come back to shape after your body weight is lifted. This slow return rate is what allows a comfortable, yet supportive contouring of all the bumps and curves of the body that eliminates the rebound pressure that hard springs and rubberized foam has when you compress it with your body. Visco-elastic memory foam can commonly be seen in 3lb, 4lb., and 5lb. densities. Our special Biogreen® proprietary, pressure sensitive, viscoelastic memory foam material is an approximate 5lb. density and is free of dangerous chemicals like PBDE, TDI, Boric Acid and Bromine. An independent laboratory even measured no V.O.C. (Volatile Organic Compounds) outgas ratings. In fact, not only does our Biogreen® memory foam lack that common smell often associated with new foam, but during the independent laboratory test, the only detectable reading came from an approximate one percent water vapor. With so much concern about the release of chemicals in our atmosphere and toxins absorbed by our bodies, you can feel good knowing that our Biogreen® memory foam offers a truly hypo-allergenic, environmentally friendly, and non-toxic experience. Our Biogreen top foam layer is approximately a 5lb. density and is ultra pressure sensitive. Underneath this layer, we use a slightly more dense and over twice as firm 5lb. memory foam for extra support. This will allow the mattress to be more instantly comfortable in all temperature environments, but still very supportive and durable in structure. We then ventilate the Biogreen foam layers and place underneath it a medium-firm, high resilient, polyurethane airflow channel support layer, with an extra support underneath, while still retaining our Patented Airflow Transfer System™.