The smoke density tester for building materials was developed by Rohm and Haas Company for internal control. It was developed in accordance with the ASTM D2843 standard in the 1970s. Its theoretical basis is the adoption of Bill Lumber's law, namely The flame directly impacts the sample, and after the material burns to produce smoke, the smoke density value (SDR) can be judged by blocking the transmittance of the light. For more details please visit http://www.laboratorytest-equipment.com/supplier-398752-construction-materials-testing-equipment