Titan burns why

What is the

Fire class D?



Fire class D includes fires involving metals that burn with strong embers.


Graphics: Archive.


Fires of aluminum, magnesium, sodium, potassium, ...



Which metals burn?

 There are four different groups of metals; three of these are flammable to varying degrees:


Light metals that react dangerously with water even when cold

Numerous light metals (with a density less than 5 kg / dm³) react on contact with water to form hydrogen gas (H2), which in turn forms a highly explosive mixture of oxyhydrogen with the oxygen present in the air and mostly through the mixture produced during the reaction Heat is ignited.

The elements lithium, sodium, potassium, rubidium, cesium, calcium, strontium and barium belong to this group.

Light metals that do not react with water when cold

In the event of fire, the metals in this group reach very high temperatures (over 2000 ° C up to 3200 ° C) and therefore pose a particular risk.

The metals beryllium, magnesium, aluminum and titanium belong to this group.

Base heavy metals

These can also catch fire.

Examples are iron, lead and zircon, which incidentally generates the highest temperature possible in a metal fire - an unbelievable 4660 degrees Celsius!

Noble heavy metals

... like silver, gold, platinum do not burn.


How can you delete?


Unsuitable extinguishing media

The introduction of water must be avoided at all costs! Not only does it further fuel the combustion, it also brings with it the risk of explosion. Therefore, water-based extinguishing agents such. B. foam, for fighting metal fires. Carbon dioxide (CO2) is unsuitable. Nitrogen is also not to be used as an extinguishing agent, as nitration occurs with the hot metals. There are therefore only a few options for fighting fires.

Suitable extinguishing media

Metal fire powders are suitable, as they are often kept in stock in companies with a corresponding risk potential. These are salts such as sodium chloride or potassium chloride that melt on the source of the fire and form an impermeable layer that suffocates the fire.

A similar effect can be achieved by using cement, also with gray cast iron chips, and of course with dry (!) Sand.


What are the special features?



The peculiarity of metal fires, which has led to the creation of a separate fire class, is the extraordinarily high temperature that is reached. A temperature of at least 1000 ° C can be expected for most metal fires, light metals burn at 2000-3000 ° C and the heavy metal zircon even at over 4600 ° C. These high temperatures trigger chemical reactions that do not correspond to our usual experience because they cannot take place at lower temperatures. Therefore, when deleting you can experience very unpleasant, if not life-threatening, surprises.

UV radiation

The high temperature is also responsible for the fact that a high proportion of UV radiation is emitted - the eyes must therefore be particularly protected!



How can metals be ignited?

 The flammability of metals depends heavily on their appearance. A solid steel beam cannot be ignited, but fine iron powder can be ignited very easily. In general, the larger the surface of the metal in relation to its volume, the easier it is for oxidation, i.e. combustion, to take place.

There are several possible causes of a metal fire. With some light metals, as mentioned above, contact with water is sufficient to cause an ignition. Aluminum powder and magnesium powder can be ignited with the flame of a gas burner. Steel wool can be ignited by contact with the two poles of a flat battery - a common cause of fire in workshops!



Classification according to density


Light metals

Light metals have a density of less than 5 kg / dm³.

The light metals that react with water in a cold state include the elements lithium, sodium, potassium, rubidium, cesium, calcium, strontium and barium.

The metals beryllium, magnesium, aluminum and titanium are among the light metals that do not react with water when cold.

Heavy metals

Heavy metals have a density greater than 5 kg / dm³.

Base heavy metals can also catch fire; Examples are iron, lead and zircon.

Noble heavy metals do not burn; they include, for example, silver, gold and platinum.


Temperatures in the course of the fire

 The combustion of magnesium should be taken as an example here. Magnesium burns at temperatures of over 2000 ° C. This high temperature can also be recognized by the bright white glowing color. The emitted light contains a very high proportion of UV and can therefore damage the eyes!

At 2000 ° C, around 10% of all water molecules present are split due to the high temperature alone, thereby releasing the constituents of water, i.e. hydrogen and oxygen. The mixture of these two gases is known to be the explosive oxyhydrogen.