In automated warehouses, archives, and other highly networked areas, high concentrations of valuable goods often come into contact with sensitive electronics and, in some cases, highly flammable materials. A fire here not only causes damage to stored goods, but also leads to system downtime and lengthy business interruptions, which can result in immense follow-up costs.
Active fire prevention offers a decisive advantage: it takes effect before a fire can even start, thereby minimizing the fire risk for technology, stored goods, and infrastructure.
Specific ignition thresholds play a central role in this. They indicate the point at which a substance is no longer flammable under defined conditions and thus form an important basis for the principle of active fire prevention through oxygen reduction with OxyReduct®. To understand why this is so effective, it is worth taking a look at key facts about ignition thresholds – from the basics to in-depth insights:
Testing the flammability of different materials.
If the term “ignition threshold” is entered into search engines without additional context, a surprising number of entries dealing with “explosion limits” appear. However, this is not the ignition threshold that is used in fire prevention. In the context of fire protection, the ignition threshold is defined differently, as already indicated in the introductory text: depending on the guideline (e.g., VdS), the ignition threshold specifies the oxygen content in the ambient air at which fires can no longer occur or at which embers can no longer spread.
The fire triangle shows that oxygen, heat, and fuel are necessary for a fire to start.
Anyone who takes a closer look at fires will sooner or later come across the fire triangle. This is where ignition thresholds under defined conditions come into play in fire prevention. If two sides of the triangle remain unchanged (in this case, fuel and ignition source/heat), a fire can be prevented by influencing the third side (oxygen). Reducing the oxygen content changes the ambient atmosphere in such a way that a fire can no longer occur.
Fire test to determine the ignition behavior of PVC containers.
Different materials have different ignition thresholds under the same conditions. According to VdS Guideline 3527, for example, the ignition threshold for PVC is 16.9 vol.% O2 and for paper it is 14.1 vol.% O2.
However, even the same material can have different ignition thresholds: while solid materials (e.g., wood, plastics, or paper) usually only burn when exposed to direct heat or an open flame, dusts of the same material become highly reactive even in finely dispersed form. The reason: the large surface area of the particles allows for extremely fast reactions – a wooden board smolders, but fine wood dust can form explosive mixtures.
Determination of ignition thresholds in deep-freeze areas.
In deep-freeze areas, the ignition threshold of the same substance is usually higher than at room temperature. The explanation for this can be found in the context of the fire triangle. Since the energy or heat is significantly reduced here, either the oxygen content or the ignition energy must be increased to achieve the correct “mixing ratio.”
The situation is similar with (air) humidity. Moisture in the material or in the ambient air has a slightly cooling effect. It displaces a proportion of the gases, including oxygen, in the same volume and thus influences the ignition threshold.
Accurate evaluation of measurement results from fire tests.
As the preceding facts have already made clear, ignition thresholds depend on numerous conditions. For this reason, the WAGNER Fire Laboratory conducts standardized fire tests tailored to the individual customer and their application in order to define the oxygen concentration of the protected area. The same storage conditions and the stored goods, including outer packaging, etc., are simulated – even those of a deep-freeze warehouse – and the test is set up 24 hours before it is carried out. This ensures that the oxygen concentration is matched to the material with the lowest ignition threshold under the same conditions as those prevailing at the customer's site. This is because packaging, adhesive joints, printing, or coatings can also be decisive risk factors.
“Lighter test”: If the oxygen content in the ambient air is too low, no flame can be produced.
Although determining the ignition threshold plays a central role in active fire prevention, oxygen reduction systems operate with an additional buffer. In common guidelines such as VdS or FM Approvals, this is referred to as the “design concentration”. In fire prevention, “safety first” therefore applies twice over: preventing fires before they start and even going one step further. It goes without saying that our OxyReduct® fire prevention systems also comply with standards and are both VdS-certified and FM-approved. You can find out exactly how OxyReduct® works and which system variant is suitable for your area of application on our website.
Would you like to know what the ignition thresholds mean for your own situation? We would be happy to advise you and help you determine the appropriate fire protection conditions.
