The Standard Test Method for Smoke Density Register

During a fire, visibility reduces due to smoke. The risk of injury and death increases. The smoke density of a material gives an indication of its visibility through smoke. Specialized machinery carries out the standard test method, which measures the level of smoke density of a given material, in order to predict its performance in a real fire.

Test Requirements

• The smoke density test generally requires nine material specimens to be tested in a smoke density chamber. Each specimen is measured out at 75 mm by 75 mm by the thickness of the end use, which generally does not exceed 25mm, or else the excess material needs to be removed from the reverse side.

Standard Method

• The smoke density chamber is positioned vertically and operates with one side facing the heat source. A smoke obscuration graph is produced from the white light beam stretching from the bottom of the chamber to the light sensor at the top. Determine the quantity of soot deposited on the lens by applying several equations to the smoke obscuration data. The test lasts for approximately 20 minutes.

Calculating Results

• The smoke obscuration graph produced is a curve plot of smoke density versus time. The time taken to reach 10, 40 and 70 percent light transmittance, and the time when the majority of smoke emits, are determined from the graph and used to calculate the smoke index. A high smoke index value indicates a high-smoke production rate, which translates into an increased hazard for someone escaping a fire. Results are expressed in specific optical density.

When to Test

• Specialists apply the standard test for smoke density according to the material tested. Army personnel use it to test material meant for military areas such as submarines and naval ships. The test also detects smoke density of fuel gases, particularly gases used for heating, such as propane and kerosene.