page_title: Combustibility and flammability
hierarchical_section_title: Combustibility and flammability
caption_attribution_description: Fire test vertical shaft furnace to test flammability as per DIN 4102 to achieve B1 rating (schwerentflammbar = difficult to ignite) at Technische Universität Braunschweig, iBMB, Germany
context_page_description: A combustible material is something that can combust in air. Flammable materials are combustible materials that ignite easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable material catches fire immediately on exposure to flame.
  The degree of flammability or combustibility in air depends largely upon the volatility of the material - this is related to its composition-specific vapour pressure, which is temperature dependent. The quantity of vapour produced can be enhanced by increasing the surface area of the material forming a mist or dust. Take wood as an example. Finely divided wood dust can undergo explosive combustion and produce a blast wave. A piece of paper catches on fire quite easily. A heavy oak desk is much harder to ignite, even though the wood fibre is the same in all three materials.
  Common sense would seem to suggest that material "disappears" when burned, as only the ash is left. In fact, there is an increase in weight because the combustible material reacts chemically with oxygen, which also has mass.
context_section_description: A combustible material is something that can combust (burn) in air. Flammable materials are combustible materials that ignite easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable material catches fire immediately on exposure to flame.
  The degree of flammability or combustibility in air depends largely upon the volatility of the material - this is related to its composition-specific vapour pressure, which is temperature dependent. The quantity of vapour produced can be enhanced by increasing the surface area of the material forming a mist or dust. Take wood as an example. Finely divided wood dust can undergo explosive combustion and produce a blast wave.  A piece of paper (made from wood) catches on fire quite easily. A heavy oak desk is much harder to ignite, even though the wood fibre is the same in all three materials.
  Common sense (and indeed scientific consensus until the mid-1700s) would seem to suggest that material "disappears" when burned, as only the ash is left. In fact, there is an increase in weight because the combustible material reacts (or combines) chemically with oxygen, which also has mass. The original mass of combustible material and the mass of the oxygen required for combustion equals the mass of the combustion products (ash, water, carbon dioxide, and other gases).  Antoine Lavoisier, one of the pioneers in these early insights, stated that Nothing is lost, nothing is created, everything is transformed, which would later be known as the law of conservation of mass.  Lavoisier used the experimental fact that some metals gained mass when they burned to support his ideas.
caption: DIN4102 Flammability Class B1 Vertical Shaft Furnace at Technische Universität Braunschweig, Germany
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