Sudden Infant Death Syndrome (SIDS) is the highest cause of death in the post- neonatal period. According to the Triple Risk Model (Kinney et al., 2009), SIDS results when three factors simultaneously influence the infant: (a) an underlying vulnerability in the infant, (b) a critical developmental period, and (c) an exogenous stressor. Considering exogenous stressor evidences, the objectives were: to determine the thermal behavior of current baby mattresses, to test improvements reached by new materials, to confirm the viability to design harmfulness mattresses according to Oeko-tex, to confirm that rebreathing of exhaled air is above the safety threshold concluding with a design criteria including the properties mentioned above.Thermal test It was used a thermal mannequin ST-2 made by Measurement Technology Northwest. Test specimens were: (1) spring mat.-foam-textile cover sewed. (2) Fiber mat.-foam 3d textile. (3) PU mat. core low density PU-PVC cover. (4) PU Mat. core with low density PU. (5) Babykeeper®mat. core. (6) Babykeeper®mat. core-3D foam textile. (7) Babykeeper®mat. core-Smart textile. Toxicity and Rebreathing test Oekotex test was performed by AITEX following label standards. To study rebreathing avoidance an infant mannequin was simulated as a head box which was placed with its open face on the mattress and connected with tubing to a gas reservoir filled with 5% CO 2 . Also it was used 50cc syringe with two one-way valves which simulates infant breathing. Finally a CO2 analyzer was placed in the head box (tested by Bar-Yishay Phd). Both tests were executed to confirm liability of new materials: spec. 2 and 7.Thermal Test Results (Test Specimen (Temperature average last 30min, Thermal Resistance Rt (Cm 2 /W)): 1: (38.4 o C, 3.2) 2: (40.1 o C, 3.34) 3: (38.4 o C, 3.2) 4: (38.1 o C, 3.17) 5: (37.2 o C, 3.1) 6: (38.5 o C, 3.20) 7: (38.3 o C, 3.19) Oekotex: Not toxic class1; and Rebreathing results (specimen (Max CO2(%),Time to reach plateau (sec)): Fiber core with 3D Foam (4.36±0.11, 324±1.4) Babykeeper®mat. (3.35±0.14, 298±19) In this sense both systems had a significantly faster rate of CO 2 elimination (4–5min) compared to 15–18.7min. for other mattresses (P<0.001) (Bar-Yishay et al., 2011).As a conclusion design recommendation are: RT<3.2 o Cm 2 /W Oekotex label class 1 for product and components Rebreathing test simulation (fixing CO 2 : concentration at 5%): CO 2 <4% (steady state situation non-toxic) and CO 2 elimination rate<400s. (Bar-Yishay et al., 2011).Authors give thanks to IBV and AITEX for collaboration during laboratory test.