In hazardous materials warehouses, safety poses major challenges for both operators and fire protection officers. The stored goods are combustible, moderately or highly inflammable, or perhaps even capable of spontaneous ignition. They often have fire- or explosion-conducive characteristics as well. And materials may react strongly to their own combustion residues, resulting in poisonous by-products or gases. Fire prevention concepts based on reducing hazard potential from the beginning have proven effective at keeping these dangers at bay.
When it comes to systematic fire prevention, the goals are clear: protecting humans, animals, health and the environment. Business-related concerns are important as well, such as protecting the stored goods against loss, preventing damage to the warehouse itself (including its investment-intensive automation systems), and above all, maintaining normal business operations and thus ensuring the company’s continued delivery capabilities. Disruptions to operating processes should neither occur due to false alarms nor as a result of fire suppression scenarios involving time-consuming, expensive cleaning and disposal work.
BASF Coatings AG had to keep all of these factors in mind when comparing different fire prevention systems for their new distribution centres at their Münster-Hiltrup location. The global chemicals corporation's new high rack storage facilities were to house innovative, high-value lacquers for industrial and automotive applications, so water- and foam-based extinguishing systems were out of the question: even if the fires were successfully suppressed, the lacquers would be rendered unfit for sale. Another potential drawback would have been the need to install retaining structures to collect the contaminated extinguishing water, which would then need to be handled as toxic waste for disposal purposes. The automatic CO2 extinguishing systems still frequently employed would have required them to keep an enormous amount of carbon dioxide on hand—that is, enough to flood the warehouse’s approximately 165,000 m³ of storage volume in fire-suppressive concentrations. And, ultimately, they considered the inert gas’s harmful effects on human health incompatible with company policy.
One central aspect of BASF’s security concept is to ensure that the lacquers, which are classified as hazardous materials, do not represent a fire danger. To achieve this, they had to ensure that there was no way a fire could break out. This is why, based on their goals of preventing explosions, maintaining business operations, preserving human health, and protecting the environment, BASF decided to employ active fire prevention by means of oxygen reduction. “We were faced with a difficult task that we could not accomplish using conventional safety and security technology,” said Dr. Peter Bachhausen, Head of Safety and Environmental Protection at BASF Coatings AG. “We needed a different trick: Oxygen levels in the new warehouse will be permanently lowered to 13% by volume, because fires cannot develop in places where there isn’t enough oxygen. Our plant fire department conducted an extensive series of tests, trying to set fire to a test warehouse—all in vain.” As an additional security measure, BASF also decided to stop using methanol, methyl acetate and methylal in their lacquers, as they would have remained flammable even at oxygen concentrates below 13% vol.
Over the past few years, systems like the one they installed for BASF have helped the WAGNER Group GmbH become a leader in active fire prevention. The 1994, the fire prevention specialists and system manufacturers at Wagner became the first company in Germany to employ nitrogen as an extinguishing agent. When used in gas extinguishing systems, nitrogen displaces the oxygen in the protected area when a fire breaks out so as to deprive the fire of the air it needs to “breathe”.
Wagner drew upon its extensive knowledge of fire formation and suppression when developing the OxyReduct® fire prevention system. The oxygen-reduction system generates nitrogen and continually feeds it into the protected area, thus minimising the risk of a fire breaking out in the first place. The nitrogen is introduced in a controlled manner in order to keep the oxygen level below the ignition threshold at all times, meaning that it is not physically possible for a fire to break out. Eliminating the possibility of fires also eliminates any potential for consequential damage through smoke, soot or extinguishing agents. Rather than keeping large quantities of extinguishing agents in reserve, OxyReduct® generates the nitrogen it needs on site by drawing it from the ambient air. This saves space and makes the system more flexible, for instance if the building is converted or used for a different purpose.
When it comes to handling hazardous materials, there are a variety of safety regulations in place, such as the Technical Regulations on Flammable Liquids (TRbF) or the Technical Regulations on Hazardous Materials (TRGF). VdS guidelines regulate, among other things, the usage and storage of flammable materials in separate areas from a fire-engineering perspective. Fuchs Lubritech GmbH, one of the world’s leading manufacturers and suppliers of specialized lubricants, aimed to store a variety of hazardous materials—some with extremely low ignition thresholds—in a single high rack storage facility, without physically separating them. As such, the 46,000-m3 high rack warehouse in Kaiserslautern employs a combination of two different fire-protection systems.
The OxyReduct® fire prevention system represents one part of the concept: continuously reducing oxygen concentration levels to 13.5% vol. ensures that most materials cannot ignite spontaneously. However, a few of the materials have ignition thresholds below this level. In order to ensure optimum fire protection for these materials as well, the company also elected to install a CO2 extinguishing system controlled using an air sampling smoke detector; if a fire alarm is triggered, it floods the area with CO2 up to a height of around five metres. This lowers the oxygen concentration to 8 % by volume, a level especially effective for suppressing fires. For this reason, particularly combustible and hazardous materials are only stored in the lower part of the warehouse.
Multi-stage concept for an OxyReduct® system with CO2-flood extinguishing
The concept also accounts for the safety of the employees working in warehouses protected in this manner. As fire prevention systems based on oxygen reduction by means of nitrogen infeed appeared on the market and began increasing in popularity, the Deutsche Gesetzliche Unfallversicherung (German Statutory Accident Insurance) issued Directive BGI/GUV-I 5162, Working in Oxygen-Reduced Environments, based on a study it commissioned, experiences reported in the field, and other international research efforts. The University of Munich’s study shows that it is possible to remain in a reduced-oxygen environment without health risks, but such environments are to be classified based on the degree of oxygen reduction. In principle, oxygen concentrations as low as 17 % vol. are safe, and there is no need to specify time limitations on how long employees may remain within those protected areas. Persons working in environments with lower oxygen content must undergo a physical examination to ensure that they have no undetected circulatory conditions that could put them at risk. Healthy individuals can work in environments with oxygen levels as low as 13% vol. without issue, provided that they adhere to the specified break schedule.
Examples from the recent past have demonstrated just how dangerous a lack of active fire prevention can be for both humans and the environment: In Krefelder Hafen in 2012, a fertiliser company warehouse caught fire. The entire storage facility ultimately succumbed to the flames. Although the building did have a fire detection system, by the time it was triggered, the building was already burning. By the time the fire brigade arrived, the entire hall was in flames; there was nothing left to be saved. It was only with immense effort that the fire-fighting forces were able to prevent even more extensive environmental damage. In 2013, a fire broke out in a warehouse in Ludwigshafen, and quickly spread throughout the 9500 m² industrial park. Four thousand eight hundred tonnes of granulated Styrofoam—which is not considered highly flammable, but can accelerate combustion—fed the flames and caused extreme amounts of smoke to develop. It became necessary to evacuate the surrounding area, and hazardous soot particles in the smoke contaminated the city and the environment, even as far as 30 km away. Thus, the best method of keeping people safe while protecting processes and the environment is to prevent fires from developing in the first place. Active fire prevention by means of oxygen reduction is one of the most effective methods of doing so.
This article was published in Issue 5 of the specialist magazine bauplaner Brandschutz (building planners’ fire protection), a Schiele & Schön publication.