Everyday working conditions MUST be taken into consideration when designing an underground mine ventilation system. Aside from the unavoidable shock loss with in a system, quality working conditions are key to happy workers, which translates into happy production. The quality of air closely depends on the quantity (measured in cubic feet per minute or c.f.m.) of air being pumped down to the bottom of the mine. To get a basic idea as to what mining engineers deal with, here is a quick sample problem to try out.

An underground survey showed the quantities of the following gases at the head:

  Gases                  Quantity (c.f.m.)

• Methane                     150
  
• Hydrogen Sulfide       0.75
• Carbon Dioxide         53.40
  
• Carbon Monoxide      2.1
  
• Nitric Oxide               0.14
• Nitrogen Dioxide       0.13

Broken rock inside a mine gives off Hydrogen Sulfide, the diesel engine equipment used underground gives off exhaust fumes, and an unexplained breakout of methane gas. There is a 6 man crew at work (the average person consumes 0.07 c.f.m. of oxygen) and standard diesel engine requires 75 c.f.m. in order to operate properly. Find the quantity of air needed to maintain MSHA regulations.

There are regulations set by MSHA as to how much (percentage wise) each gas can occupy relative to the total volume of air at any give area in an underground mine. Using these regulation values, a basic equation can be derived:
                    
                                         ( ALL GASES CONSUMED )   =   ( ALL GASES EXHAUSTED )

0.2095*QT - [(the # of workers)*0.07] = 0.195 ( QE + H )

• "0.2095" & "0.195" are constant derived from MSHA regulations
• "QT" is what is being found (c.f.m.)
• "0.07 c.f.m." is the oxygen consumption for one worker
• "QE" is the gas exhaust from the diesel engine
  
• "H" is the total quantity of all the gases