TM 1-1510-225-10 2-85 Table 2-5.  Oxygen Flow Planning Rates Vs Altitude   (All Flows in LPM Per Mask at NTPD) CABIN PRESSURE ALTITUDE IN FEET CREW MASK NORMAL (DILUTER DEMAND) (1) CREW MASK 100% (1) PASSENGER MASK 35,000 -0-(2) 3.1 3.7 (3) 34,000 -0-(2) 3.4 3.7 (3) 33,000 -0-(2) 3.7 3.7 (3) 32,000 -0-(2) 3.9 3.7 (3) 31,000 -0-(2) 4.2 3.7 (3) 30,000 -0-(2) 4.4 3.7 (3) 29,000 -0-(2) 4.7 3.7 (3) 28,000 -0-(2) 5.0 3.7 (3) 27,000 -0-(2) 5.3 3.7 (3) 26,000 -0-(2) 5.6 3.7 (3) 25,000 -0-(2) 5.9 3.7 24,000 -0-(2) 6.2 3.7 23,000 -0-(2) 6.6 3.7 22,000 -0-(2) 6-9 3.7 21,000 -0-(2) 7.2 3.7 20,000 3.6 7.6 3.7 19,000 3.9 7.9 3.7 18,000 4.2 8.3 3.7 17,000 4.5 8.7 3.7 16,000 4.8 9.1 3.7 15,000 5.1 9.5 3.7 14,000 5.4 10.0 3.7 13,000 5.8 10.4 3.7 12,000 6.1 10.9 3.7 11,000 6.5 11.3 3.7 10,000 6.9 11.9 3.7 NOTES: (1)    Based on minute volume of 20 LPM-BTPS (Body Temperature and Pressure Saturated). (2)   Use 100% oxygen above 20,000 feet. (3)   Not recommended for other than emergency descent use above 25,000 feet. If  average climb or descent flows are desired, add the values between altitudes and divide by the number of values used.  For example, to determine the average rate for a uniform descent between 25,000 feet and 15,000 feet perform the following: (5.9 + 6.2 + 6.6 + 6.9 + 7.2 + 7.6 + 3.9 + 4.2 + 4.5 + 4.8 + 5.1)   11 = 5.7 LPM. This method is preferred over averaging the extremes as some flow characteristics vary in such a way as to yield an incorrect answer.