As a common flame retardant material, silicone is one such material that can conform to the most stringent requirements of smoke toxicity tests in a variety of industries. 

When fires break out, it’s often not burns from the fires that cause the most harm, but the resulting smoke. In many instances of deadly fires, it has been the resulting smoke that causes more deaths than the fire itself. The dangers of smoke are widely recognised and strict standards have been constructed within a variety of industries that aim to minimise high quantity production of toxic smoke in cases of fire. 

Inhalation of toxic smoke has disastrous effects on the human body. Immediate effects of smoke inhalation include extreme shortness of breath, cough, headache and nausea. For some toxic compounds, smoke inhalation can also cause disorientation, panic, loss of mental function and fainting, as well as skin, eye and lung damage. Simple asphyxiation in conjunction with incapacitating side effects can lead to an excruciating death. Toxic smoke is frequently produced by burning organic elastomers, which results in many seals and gaskets constituting a fire safety risk.

Figure 1: Silicone burning with very little visible smoke production

Smoke is not only toxic, but in many cases also obscures light and obstructs visibility. This reduction in visibility makes it more difficult for persons to walk around obstacles, or find their way to a safe location. Additionally, this slowing of movement due to visibility means that people are more exposed to hazardous conditions and inhale more potentially toxic smoke. While smoke toxicity is a severe immediate threat to human safety, visual impairment for smoke can similarly lead to increased harm or death in a catastrophic fire. 

Silicone materials do not ignite until fairly high temperatures (>400°C). While burning, silicone products primarily decompose into silica (SiO2) and carbon oxides. The silica is a solid material which deposits on the surface of the material. The carbon oxides at this temperature are usually transparent, and do not significantly impact visibility. As silicones do not contain harmful sulphur or halogen containing substances, their decomposition by-products are largely non-toxic. Fire resistance, including smoke mitigation, can be enhanced by the use of flame retardant silicone grades which have been researched and developed by Jehbco to reach and exceed customer requirements. 

At Jehbco, products have been tested to a variety of smoke toxicity and visibility standards including BS 6853 and EN 45545 for the rail industry, and other testing standards including AS 1530.3 and ISO 5660. The results of all tests performed on silicone rubber have shown outstandingly low toxicity and good visibility results. For BS 6853 Annex B, the weighted R rating 0.27, significantly below the most stringent requirement, R ≤1. Other testing performed were all significantly below required specifications, as expected based on the exceptional material properties and flame retardance, including receiving a HL3 rating under EN 45545-2 R22/R23 testing. 

Before devastating fires have a chance to break out, every design should be carefully assessed to ensure all possible measures to minimise dangers to human safety have been implemented. The replacement of toxic smoke producing elastomers with flame retardant silicones is one such measure that can significantly reduce risk in cases of fire.

For more information on silicones and silicone flame retardance, please browse through our website or contact us.