What is the role of the ventilation?


Ventilation is intended to maintain a composition and quality of the atmosphere compatible with the safety, health and activity of the personnel.

To do this, you need to:

  • To renew the oxygen in the air necessary for life,
  • Dilute dangerous, harmful or explosive products,
  • Evacuate calories to obtain an acceptable temperature.
What is the role of the ventilation?

The SUB’ROCA engineers are at your disposal to assist and advise you in the dimensioning of your ventilation installations. Whether your project concerns a meshed network in an underground mine or a complex digging project in another environment, our teams have the technology to calculate the air requirements and performance necessary to ensure ventilation that complies with the health and safety of personnel.

Renew the oxygen in the air

Dry air near the ground is a colourless, homogeneous gas mixture.

It is approximately composed in volume of :

  • 78.08% oxygen O2;
  • 20.95% N2 ;
  • less than 1 % of other gases of which :
    • Noble gases mainly argon 0.93%, neon 0.0018% (18 ppm), krypton 0.00011% (1.1 ppm), xenon 0.00009% (0.9 ppm) ;
    • Carbon dioxide 0.038% (380 ppm).

It also contains traces of hydrogen 0.000072 % (0.72 ppm), but also ozone and a trace amount of radon.

Oxygen in the air is essential for human respiration:

  • 02 < 18% è respiratory gene and pulse acceleration
  • 02 < 14% è anoxemia (risk of so-called « post-anoxic coma »)

Oxygen is also essential to feed the other useful combustions at the bottom:

  • Diesel engines

Dilute hazardous, noxious or explosive products

Other products are dangerous due to the risk of explosion (firedamp, dust).

  • Some gases are dangerous because a high concentration of them in the atmosphere decreases the oxygen content and leads to anoxemia.
  • Other products are harmful by aggression of the human organism with more or less distant deadlines.


Immediate effects

Carbon Monoxide (CO), Carbon Dioxide (CO2), Oxidised Nitrogen Derivatives (NO-NO2), Hydrogen Sulphide (HS2)


Delay effects

Silica-rich dusts (silicosis and pneumoconiosis), uranium (radon gas, radioactive dusts)

Evacuate calories

Origine of the calories

The heat to be evacuated from the bottom by ventilation comes from different sources:

  • The ground,
  • The energy supplied at the bottom,
  • The increase in pressure related to depth.


The grounds

  • The geothermal gradient (the number of degrees by which the temperature of the ground rises at a depth of 100m).
  • Slaughtered products; the reduction into small pieces facilitates the exchange,
  • In the walls of structures being dug or newly dug,
  • In the waterways


The energy supplied to the bottom

  • Combustions (explosives, diesel engine) release calories.
  • Most of the electrical energy is also converted into heat.


The variation of pressures

Everyone has observed that the compressed air in a bicycle pump gets hot.

With depth, the air pressure gradually increases, resulting in an elevation of up to 1°C /100m vertical.


Working in a hot environment

A man at rest spends a little energy to keep his body functioning.

The man at work, making a physical effort, expends additional energy the more intense the work is.

If the atmosphere is cold, the body is cooled, but if it is hot, it does not cool and may even heat up even more.

The atmosphere of a building site is characterized by a measurement called the resulting temperature. It involves the true (dry) temperature, the moisture content as indicated by the so-called wet temperature and the air speed.

tr = 0,3*ts + 0,7*th – v

tr   =         Resulting temperature

ts   =         Dry temperature (as measured by thermometer)

th   =        Wet temperature

v     =        Air speed in meters per second

The measuring device used will be detailed in the chapter « Ventilation measures ».


Of those three goals:

  • Renewing the oxygen in the air
  • Diluting hazardous materials
  • Evacuate calories,

One or the other can be decisive depending on the nature of the mine, its firedamp release, and the temperature of the land.


It is then this dominant factor which imposes the necessary air flows:

  • The firedamp
  • Radon
  • The heat
  • Diesel exhaust.

Ventilation solutions

Our ventilation systems are designed to ensure air renewal in quarries and underground mines. SUB’ROCA offers you a whole range of dedicated axial fans. SUB’ROCA assists you in the dimensioning of your installations.

SUB’ROCA offers ventilation solutions adapted to your work in the basement or « top-down », including the construction of station boxes or shafts.

SUB’ROCA supplies ventilation systems equipped with ducts for tunnels in excavation, up to JetFan (accelerator) for tunnels that are opening. Our equipment can be installed on TBMs.

SUB’ROCA has designed a compact range of high-performance fans in diameters from 250mm to 800mm for ventilating microtunneling excavations and underground networks.