2.3 Gas Detection
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2.3.5 Atmospheric Monitoring Systems
An Atmospheric Monitoring System (AMS) consists of a network of sensors (which
mainly detect gases) located inside the mine. These sensors send data continuosly to a
device on the surface, which processes the data in real-time (e.g. Rowland et al. 2018).
An AMS makes it possible to determine if an area is safe or not. It also actuates the
mine’s alarm systems and interacts with the ventilation system to configure it based
on what the mining operations require.
The AMS was originally used in coal mines to monitor CH 4 , but the use of
them has been extended to all types of underground mining, where they also control
possible fires in electrical installations.
2.4 Basic Psychrometry
Psychrometry is the branch of thermodynamics and climatology that studies mixtures
of gases and vapours. It relies on two essential parameters: temperature and humidity.
The former is important because the ventilation rate needs to increase as the temperature rises. Normally, recommended maximum temperatures underground are:
30–32 °C (dry-bulb) and 27–28 °C (wet-bulb) (Hartman et al. 2012). The other
parameter that determines the needs of ventilation (or air conditioning) is an increase
in humidity. The next section describes these and other psychrometric parameters.
Dry-bulb Temperature (T d )
An ordinary thermometer measures dry-bulb temperature. This type of measurement
is completely independent of air humidity and airvelocity, as well as from the heat
radiation of nearby objects.
Wet-bulb Temperature (T w )
Wet bulb-temperature measurement involves air humidity content, which is determined by using a wet-bulb thermometer. This is a common thermometer that is
covered with a cotton bulb moistened with water, meaning that the temperature is
affected by the cooling effect of the water evaporating in the air. Therefore:
• If the air is drier, the bulb will dry faster and the temperature will be lower.
• Air currents will accelerate the water evaporation from the bulb, dropping the
temperature as a result of the latent heat for water passing from a liquid to a gas
state.
Dry- and wet- bulb temperatures coincide when the air is saturated.
Equivalent Temperature (T e )
This measurement involves environmental temperature, relative humidity and air
velocity. It offers an approximation of the thermal sensation perceived by a human
45
2.3.5 Atmospheric Monitoring Systems
An Atmospheric Monitoring System (AMS) consists of a network of sensors (which
mainly detect gases) located inside the mine. These sensors send data continuosly to a
device on the surface, which processes the data in real-time (e.g. Rowland et al. 2018).
An AMS makes it possible to determine if an area is safe or not. It also actuates the
mine’s alarm systems and interacts with the ventilation system to configure it based
on what the mining operations require.
The AMS was originally used in coal mines to monitor CH 4 , but the use of
them has been extended to all types of underground mining, where they also control
possible fires in electrical installations.
2.4 Basic Psychrometry
Psychrometry is the branch of thermodynamics and climatology that studies mixtures
of gases and vapours. It relies on two essential parameters: temperature and humidity.
The former is important because the ventilation rate needs to increase as the temperature rises. Normally, recommended maximum temperatures underground are:
30–32 °C (dry-bulb) and 27–28 °C (wet-bulb) (Hartman et al. 2012). The other
parameter that determines the needs of ventilation (or air conditioning) is an increase
in humidity. The next section describes these and other psychrometric parameters.
Dry-bulb Temperature (T d )
An ordinary thermometer measures dry-bulb temperature. This type of measurement
is completely independent of air humidity and airvelocity, as well as from the heat
radiation of nearby objects.
Wet-bulb Temperature (T w )
Wet bulb-temperature measurement involves air humidity content, which is determined by using a wet-bulb thermometer. This is a common thermometer that is
covered with a cotton bulb moistened with water, meaning that the temperature is
affected by the cooling effect of the water evaporating in the air. Therefore:
• If the air is drier, the bulb will dry faster and the temperature will be lower.
• Air currents will accelerate the water evaporation from the bulb, dropping the
temperature as a result of the latent heat for water passing from a liquid to a gas
state.
Dry- and wet- bulb temperatures coincide when the air is saturated.
Equivalent Temperature (T e )
This measurement involves environmental temperature, relative humidity and air
velocity. It offers an approximation of the thermal sensation perceived by a human