FAQ - kennisbank

General risks associated with various fire extinguishing systems.


Fire suppression systems and/or fire extinguishing systems are used with the aim of controlling risks as much as possible. But are the various fire suppression systems/fire extinguishing systems themselves risk-free? Despite the sometimes so nice sales pitches of sales representatives, there are indeed risks associated with various fire extinguishing systems.

 

Below, we discuss these for each fire extinguishing system.

 

Noise risks with gas extinguishing systems.


When activating a gas extinguishing system, risks occur for overpressure, materials in the room and certainly for people

 

Sound
In gas extinguishing systems where the extinguishing gas leaves the system through the outlets, the noise level of escaping gas will be very high.

 

Case study:
ING demolishes its own data center in Bucharest ING's data center in Bucharest was demolished by a loud noise. It happened during a fire drill.

 

Damage to drivers by sound is not new, but for many people still an unknown phenomenon. Thus, anyone who yells loudly at their hard drive could, in theory, demolish it.

 

During the fire drill, the gas extinguishing system was activated. The expansion of the extinguishing gases produces an enormous noise. Since sound is a vibration it can, at high volume, be powerful enough to flatten drivers in computers.

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Sound vibrations are the vibrations of the atoms or molecules of the medium in which sound propagates. These vibrations occur in the same direction in which sound propagates.

 

Thus, sound propagates as a longitudinal wave, unlike light or water waves, which manifest as a transverse wave.

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Sound consists of waves.
A sound wave, as it passes through a medium, has a wavelength and an amplitude. Wavelength is inversely proportional to frequency: the higher the frequency (i.e., the more waves per unit length), the shorter the wavelength and the higher the perceived tone.

 

The amplitude is the maximum of the pressure that occurs over time at a given location. The strength of a sound wave is expressed in decibels or sone. Thereby, the amplitude is normalized to a reference pressure. How loud a sound is perceived is determined by its amplitude.

 

Sound waves behave just like water waves, for example: they can bend around an object (this is called diffraction), bounce off an impenetrable wall (reflection) or change direction when the "medium," the substance through which the wave travels, changes.
Waves of sound from multiple sources, or of direct and reflected sound, can amplify or cancel each other out. In the places where sound waves cancel each other out, a slightly lower air pressure is created than right next to it.

 

Risks associated with gas extinguishing systems
With gas extinguishing systems, there is a difference between the release of the extinguishing gas during a fire and in cases when there is no fire.

 

- Situation without a fire

 

The danger in a situation where there is no fire is that no advance alarms are given either. After all, these are linked to an automatic fire detection system. One will therefore be overwhelmed by the released gas with all its consequences.

 

- Fire situation

 

When the gas extinguishing system is activated by the automatic fire detection system, a clear optical and acoustic signal is given prior to activation so that people can leave the room prematurely. However, the risks to the (computer) equipment remain.

 

- Exposure to the extinguishing gas

 

Exposure to extinguishing gases produces adverse effects. For humans, adverse effects depend on the type of gas and the concentration inhaled.

 

Adverse effects might not be noticeable in healthy individuals for some time. Symptoms could include cardiac arrhythmias, dizziness, loss of concentration, panic, hyperventilation and/or shortness of breath. In most cases, with fresh air, the symptoms will usually disappear.

 

 

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However, for high-risk groups such as cara and heart patients, an increased health risk applies:

  • cardiac arrhythmias can occur with chemical fire gases
  • respiratory disorders and/or suffocation can occur with the inert gases.
  • circulatory disturbances and suffocation can occur with carbon dioxide

Decomposition products: After the release of gases, decomposition products are generated in the room which are very harmful to health and highly corrosive to materials (computers). This occurs particularly with NOVEC, FM-200, Argonite and Innergen.

 

Fogging: When blowing off a gas extinguishing system in the protected area, fogging occurs. The reduced visibility that results is a hazard during evacuation and evacuation of persons from the protected area.

 

Thrust: The discharging gas (via the nozzles) is accompanied by great thrust. Contact will therefore be likely to result in injury. In addition, the gas flow will blow away loose parts in the room.

 

Freezing: The expelling gas (via the blow nozzles or nozzles) will cool very sharply (sometimes down to -80OC) due to expansion, posing a strong hazard to materials and persons.

 

Additional risks in a fire


Almost every fire creates unburned particles and various combustion products. These particles and/or combustion products contain toxic substances, including carbon monoxide. This gas is a major health threat.

 

Heat generation
In a fire, heat will always be generated. Of course, the amount of heat depends on the fire size. As the fire becomes larger, the danger to humans and animals will also increase dramatically.


Fire extinguishing system
The purpose of a fire extinguishing system is to control and/or extinguish a fire. The risk created by fire is thereby minimized. With some types of extinguishing media, however, side effects arise. This is due to mixing of the extinguishing agent with the released residues of the fire or by the extinguishing agent itself. It is therefore important to make the right choice of the extinguishing agent and/or type of extinguishing system to be used.


Reduction of oxygen content
During fire, depending on the combustion process and the substances involved, the oxygen percentage will decrease.

 

If the extinguishing system is activated during a fire, the oxygen content of gas extinguishing systems (in particular inert gases) will drop so quickly that a very dangerous situation for people will arise. The greatest caution is therefore required with gas extinguishing systems!

 

Decomposition products of halogenated hydrocarbons
When chemical extinguishing gases are exposed to high temperatures (about 500-700 degrees Celsius), decomposition products harmful to health are produced, with even very low concentrations (acrid acid smell). One of the most important decomposition product is hydrogen fluoride (HF). This is a gas that greatly irritates the mucous membranes and eyes.

 

In addition to the gas to be applied, the amount of decomposition products also depends on:

Size of the fire: (the larger the fire, the more decomposition products are generated);

 

Time during which the extinguishing agent is in contact with the flames: (the amount of decomposition products depends on how fast a fire is extinguished);

 

Design concentration: (the more extinguishing agent is applied "safety factor & design concentration", the more effectively the fire is extinguished, resulting in less decomposition products being generated. Note this also implies that with the extinguishing gases, the oxygen concentration decreases even harder).


Confined spaces
If a confined space belongs to the group of cellars (below ground level), it must be determined beforehand how the (hazardous) extinguishing gas can be removed from the space after activation.

 

This should be laid down in a protocol. In this situation it is always a class III installation.

 

For completeness, it should be noted that chemical extinguishing gases are absolutely not suitable for nuclear fires. With this kind of difficult to extinguish fires, gas extinguishing systems have a lot of trouble, which means that the expected amount of decomposition products that chemical extinguishing gases develop in the process will increase considerably, with all its consequences.

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