BSS 7238 Smoke Density Test
What Is BSS Testing?
The Boeing Safety Standard, or BSS testing, is a testing method for gases generated by specific materials during combustion. When materials ignite, they emit gases that may harm humans at certain levels. This test identifies and measures those toxic gases to determine the safety of different materials.
BSS testing determines which toxic gases are emitted and how much of each gas is produced by burning sample pieces of materials in a controlled setting. There are several methods for measuring the toxicity levels of the gases, but spectrophotometry is used most frequently. Each compound absorbs light differently, so this method determines what compound is present and in what concentration by how it absorbs light.
BSS tests check for gases such as:
- CO, Carbon monoxide
- HCN, Hydrogen cyanide
- SO2, Sulfur dioxide
- HCL, Hydrogen chloride
- HF, Hydrogen fluoride
- NOx, Nitrogen oxides
This testing method is employed most often as a fire test for aircraft material, though similar tests are used for railway industries and government sectors. The goal of BSS testing is to discover the smoke-generating characteristics of materials during combustion to determine their viability for these fields.
What Does BSS 7238 Test For?
The Boeing Safety Standard 7238 is smoke density testing for aircraft material. It measures the specific optical density of smoke produced by combusting aircraft material by documenting the attenuation of a light beam through the smoke. In this evaluation, the tester places samples in a closed smoke density chamber and exposes them to either radiant heat or radiant heat with a flame. As the material undergoes either flameless decomposition or flaming combustion, the tester records light transmittance values to determine the smoke's optical density.
The smoke produced must stay within the maximum limits of a smoke optical density value in order to pass the test. The required smoke density value will differ based on the assessment's specifications.
BSS 7238 smoke density testing focuses on the fire response of materials used in Boeing-type aircraft. The test will assess plastic products, wire ropes, non-metallic materials and other similar substances. The materials tested are those often found in aircraft compartments occupied by passengers, so sample pieces may include wall panels, partitions, large cabinet walls and galley structures.
BSS 7238 Testing Requirements
There are a few requirements for the BSS 7238 test to take place:
- A sample size of 3 inches by 3 inches
- A minimum of three samples
- The sample thickness must be the same thickness as the original part
- A potential second set of samples depending on if the material could react differently depending on which direction it is cut
- The sample may be either a section cut from a fabricated part like the pieces installed in the aircraft or a part constructed to simulate the installed component
- Sandwich panels and other fabricated units must be tested together.
Related Tests and Standards
The BSS 7238 test is related to the BSS 7239, another flammability test. The BSS 7239 measures the smoke toxicity of composites, textiles and coatings used in the aerospace and railway industries and various government sectors. Materials used in these applications need to meet parts per million standards. The results of this test show the concentration of gases emitted during a material's combustion.
The BSS 7238 test is based on the ASTM E662 test, which also performs smoke density testing. ASTM E662 is a flammability test often required for plastics and coatings usually found in the construction and railway industries and the military sector.
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Recommended Tests to Pair with BSS 7239:
- ASTM E162 - Surface Flammability Test
- ASTM E662 - Smoke Density Test
- ASTM E1354 - Cone Calorimeter Test
- BSS 7239 - Toxicity Test
- SMP-800C - Toxic Gas Generation Test
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