Fire is one of nature’s most ferocious menaces for a human being. A multitude of events and actions can trigger incineration but the damage it causes is always devastating. When we hear that the has been a fire, our mind draws an image of a wooden or paper surface in flames so we guess a random spark or accident ignited it. Yet there are many more things that can catch fire just as easily as a towel or a chair. Such substances as calcium, titanium, sodium, lithium, potassium, magnesium and some other metals are prone to easy ignition, and it’s very hard to put such a fire out. These instances are considered class D fires, and their primary danger is that people don’t expect these substances to burn and they are not prepared to fight such fires.
Class D fires are mostly happening at industrial facilities such as factories or warehouses. According to the National Fire Protection Association report between 2011 and 2015, there were approx 31 000 industrial fires annually, causing over $1.2 billion direct property damage. The ignition of whole metal bars or ingots is an extremely rare event since they require continuous high-temperature heating. Yet the real fire danger hides in metal offal, such as dust, machine shavings, or other fine forms of metal.
Igniting such pieces of metal won’t take much more than a spark from a damaged electrical grid. After that, the fire will start rapidly spreading on surrounding surfaces due to the high-temperature burning.
Class D fire may happen in your daily life, too, for instance, if a car is caught on fire. The majority of car batteries are made from lithium, which is one of the flammable metals. Just like any other type of fire, to fight a Class D fire you will need to have the proper hardware. The most efficient tool on the edge of the defense against Class D is proper fire extinguishers.
What Does Class D Fire Extinguisher Contain
Trying to extinguish a burning metal with common agents like water is strictly prohibited. Such an act can lead to a chemical reaction that will only excite the fire, increasing its danger and consequences. That is why the contents of regular fire extinguishers (ABC class) won’t do the thing for fighting Class D fires. In its turn, Class D fire extinguishers contain dry powder with an agent aimed at inhibiting the combustion of metal from terminating the burning process. There are a couple of agents that act in slightly different ways and here are the most common ones:
● Sodium Chloride salt. Highly effective in extinguishing alkali metals such as sodium and potassium, and some other metals like titanium, aluminum, magnesium, etc.
● Copper-based powder. Used to fight only lithium-based fires.
● Graphite-based powder. Mostly used to fight burning magnesium, also suits other metals.
How Does Class D Fire Extinguisher Work
Class D fire extinguishers stand out of other types of extinguishers as they require more gentle agent dispensing yet in greater amounts. As a result, the smallest extinguisher comes in 30lbs. The majority of such firefighting tools come with a low-velocity nozzle or wand on the flexible hose that enables it to disperse powder right above the burning metal slowly. Once distributed, the powder - depending on the agent - will initiate a certain chemical reaction with the metal to separate the fuel (metal) from oxygen. For instance, the sodium-based powder will melt under the blaze forming the oxygen-excluding crust over the metal to smother the fire.
Precautions While Using The Class D Fire Extinguishers
Be aware that activating Class D extinguishes may take more time than any other fire extinguisher. Therefore, be sure that you are located in a spot where flames are not encircling you with a safe exit path. Class D fire extinguishers aren’t good for fighting any other fires besides burning metals due to their unique contents with dry powder agents. Besides, it’s crucial to remember that Class D fire extinguishers are made not of dry chemicals like the other fire extinguishers but dry powder.
The rapid and efficient reaction to incineration is an essential part of a successful firefight. That is where Class D fire extinguishers come in handy. Yet it’s critical to understand that such flame fighting hardware is only effective against small fires especially when metal burns. Don’t hesitate to abandon the job if you see that the fire is winning the fight. No property damage is worth your life. It is always better to evacuate and leave a firefighting job to the professionals.