2.2 Gases and Hygiene
33
• 14–10%: Sensation of light-headedness, blurred vision, headache, accelerated
pulse;
• 10–6%: Nausea and vomiting, loss of movement capacity, fainting and even
unconsciousness; and
• 6%: Convulsions, respiratory arrest, cardiac arrest.
The most common cause of a reduction in air oxygen concentration is oxygen
being displaced by another gas or consumed during combustion. Altitude sickness
is also a very common disorder that occurs in some mines in Latin America, and
particularly in Bolivia. The cause of this syndrome is decreased oxygen availability
at high altitude. Although the mole fraction of oxygen in air (X O 2 ) remains approximately constant within the troposphere, the total pressure (P T ) decreases with altitude.
Therefore, oxygen partial pressure (P O 2 ) falls, in accordance with P O 2 = X O 2 · P T
(Peacock 1998). This partial pressure is what drives gas exchange in the alveoli. Its
decrease generates a cascade effect whereby heart and breathing rates increase in an
attempt to make up the oxygen shortfall.
Question 2.1 Helium (He) is released inside an unsealed chamber until the concentration of He in the air of the chamber is 15% v/v . Indicate the variation of the
concentrations of O 2 and N 2 .
Answer
If the concentration of He is 15%, the sum of O 2 + N 2 is approximately 85%. O 2
comprises approximately 21% of that 85%. Therefore, the total concentration of O 2 in
the air is 17.85%. N 2 comprises 78% of the 85%, meaning the total N 2 concentration
of the air is 66.3%.
2.2.2 Mine Gases
A diverse group of gases can be found in underground environments. The main
sources of these gases are shown in Table 2.3.
When their concentration is excessive, workers experience the symptoms indicated in Table 2.4. When you go through this table, keep in mind that the longer the
exposure time, the more accentuated the health effects will be.
The main organoleptic characteristics of mine gases are shown in Table 2.5.
Knowledge of these can be very useful, as they can be used as warning signs when
there is no specific detector available.
33
• 14–10%: Sensation of light-headedness, blurred vision, headache, accelerated
pulse;
• 10–6%: Nausea and vomiting, loss of movement capacity, fainting and even
unconsciousness; and
• 6%: Convulsions, respiratory arrest, cardiac arrest.
The most common cause of a reduction in air oxygen concentration is oxygen
being displaced by another gas or consumed during combustion. Altitude sickness
is also a very common disorder that occurs in some mines in Latin America, and
particularly in Bolivia. The cause of this syndrome is decreased oxygen availability
at high altitude. Although the mole fraction of oxygen in air (X O 2 ) remains approximately constant within the troposphere, the total pressure (P T ) decreases with altitude.
Therefore, oxygen partial pressure (P O 2 ) falls, in accordance with P O 2 = X O 2 · P T
(Peacock 1998). This partial pressure is what drives gas exchange in the alveoli. Its
decrease generates a cascade effect whereby heart and breathing rates increase in an
attempt to make up the oxygen shortfall.
Question 2.1 Helium (He) is released inside an unsealed chamber until the concentration of He in the air of the chamber is 15% v/v . Indicate the variation of the
concentrations of O 2 and N 2 .
Answer
If the concentration of He is 15%, the sum of O 2 + N 2 is approximately 85%. O 2
comprises approximately 21% of that 85%. Therefore, the total concentration of O 2 in
the air is 17.85%. N 2 comprises 78% of the 85%, meaning the total N 2 concentration
of the air is 66.3%.
2.2.2 Mine Gases
A diverse group of gases can be found in underground environments. The main
sources of these gases are shown in Table 2.3.
When their concentration is excessive, workers experience the symptoms indicated in Table 2.4. When you go through this table, keep in mind that the longer the
exposure time, the more accentuated the health effects will be.
The main organoleptic characteristics of mine gases are shown in Table 2.5.
Knowledge of these can be very useful, as they can be used as warning signs when
there is no specific detector available.