Altitude and temperature have a direct effect on the molecular structure of air. An adjustment in CFM (l/sec) must be made to accommodate such changes and to provide for efficient drilling.

At high altitudes there are less molecules in a given volume of air than at lower altitudes. Therefore, when the compressor displaces a given volume at a higher altitude, the air will be less dense. When less dense air is supplied to a down hole hammer a lower operating pressure will result.

• For example: Operating a down hole hammer at 15,000 feet of elevation (4,572 m), at a temperature of 50° F (10° C), a down hole hammer would require almost 75% more volume than at sea level to operate at the same pressure.

High ambient temperature has much the same effect on air. At high ambient temperatures the air becomes less dense and at low ambient temperatures the air becomes more dense. These changes also require an adjustment to the air supply.

• For example: Operating a down hole hammer at sea level with the ambient temperature at 100° F (38° C) versus 0° F (-18° C) would require almost 20% more volume to operate at the same pressure.

The following table may be used as a reference to calculate the air volumes necessary to maintain a given operating pressure at different altitudes and at different ambient temperatures.