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6.3
Gas
Path
Length
(m)
Cloud
Concentration
(LFL)
Cloud
Concentration (v/v, by
volume)
Cloud
Concentration
(ppm)
LFL-m
ppm-m
per ISO/NFPA 497
per IEC
Methane
1
100%
5.0%
4.4%
50000
1
50000
Methane
2
100%
5.0%
4.4%
50000
2
100000
Methane
3
100%
5.0%
4.4%
50000
3
150000
Methane
4
100%
5.0%
4.4%
50000
4
200000
Methane
5
100%
5.0%
4.4%
50000
5
250000
Propane
1
100%
2.2%
1.7%
22000
1
22000
Propane
2
100%
2.2%
1.7%
22000
2
44000
Propane
3
100%
2.2%
1.7%
22000
3
66000
Propane
4
100%
2.2%
1.7%
22000
4
88000
Propane
5
100%
2.2%
1.7%
22000
5
110000
Butane
1
100%
1.9%
1.4%
19000
1
19000
Butane
2
100%
1.9%
1.4%
19000
2
38000
Butane
3
100%
1.9%
1.4%
19000
3
57000
Butane
4
100%
1.9%
1.4%
19000
4
76000
Butane
5
100%
1.9%
1.4%
19000
5
95000
Table 1—LFL-m to PPM-m Conversion
NOTE: “A” (FM/CSA) variant is factory calibrated to ISO/NFPA 497 and the “E” or “B” (IEC/
ATEX) variant is factory calibrated to IEC.