ATMOSPHERIC PRESSURE BY ALTITUDE
FOR CYLINDER PURGING
Altitude Above
Atmospheric
Barometer
Gauge Reading Gauge Reading
Reference City
Sea Level (ft) Pressure (psia) Reading (in. Hg)
at 2 psia
at 5 psia
Boston, PA
0
14.69
29.92
25.85
19.74
500
14.43
29.38
25.31
19.20
1000
14.17
28.86
24.78
18.68
1500
13.91
28.34
24.26
18.16
2000
13.66
27.82
23.75
17.64
Tucson, AZ
2500
13.41
27.32
23.24
17.13
3000
13.17
26.82
22.74
16.64
3500
12.92
26.32
22.25
16.14
4000
12.69
25.84
21.77
15.66
4500
12.45
25.36
21.29
15.18
Albuquerque, NM
5000
12.22
24.89
20.82
14.71
5500
11.99
24.43
20.35
14.25
6000
11.77
23.97
19.90
13.79
6500
11.55
23.52
19.45
13.34
7000
11.33
23.08
19.01
12.90
Mexico City, Mex
7500
11.12
22.65
18.57
12.46
8000
10.91
22.22
18.15
12.04
8500
10.70
21.80
17.73
11.62
9000
10.50
21.38
17.31
11.20
9500
10.30
20.98
16.91
10.80
Kenosha Pass, CO
10000
10.10
20.58
16.51
10.40
AIR CONTENT
Container Evacuated to 2 psia
Conatiner Evacuated to 5 psia
Container Pressure
Percentage Air Content
Percentage Air Content
psig
%
%
0
13.3%
34.2%
25
4.9%
12.7%
50
3.0%
7.8%
60
2.6%
6.7%
75
2.2%
5.6%
100
1.7%
4.4%
125
1.4%
3.6%
150
1.2%
3.1%
175
1.0%
2.7%
200
0.9%
2.3%
The approximate container air content as a percentage of the total gas vapor mixture at standard
conditions using Dalton’s and Amagat’s Laws at two points with the empty container’s air volume
evacuated to 2 and 5 psia before being filled with propane vapor to gauge pressure is as follows:
*Dalton’s Law states that the total pressure of a mixture of gases is equal to the sum of the partial
pressures and each component of the mixture at its partial pressure occupies the total volume.
*Amagat’s Law states that if each component in a mixture of gases could be segregated at the
same temperature and pressure as the mixture, the sum of the separate volumes would equal
that of the original, and the partial pressure of each component would equal the total pressure.