ULTIMA X
®
Series
GB
61
7.5 ULTIMA XIR – ATEX Performance Approval
The lower explosive limits [LEL] of the gases and vapours in the following tables
were taken from EN 60079-29-1:2007. For gases and vapours not listed in
EN 60079-29-1:2007, the lower explosive limits [LEL] were taken from the Chem-
safe [Dechema, Frankfurt] data base. Local regulations may specify different LEL
values; always ensure the correct values are used.
It is recommended that the ULTIMA XIR zero is calibrated using clean air, free of
measuring gas, and calibration gas of approximately 50 % LEL in air of the mea-
suring gas. If it is not possible to calibrate with the same gas as the measuring gas
then the Propane [C
3
H
8
] reference gas concentration together with the relative re-
sponse factors shown in the table can be used. When using this calibration method
deviations of up to ±20 % of the true gas calibration can be expected.
These relative response factors only apply at ambient temperatures of 20 °C and
unless otherwise indicated.
Reference Calibration Example for Methanol when Using Propane:
When monitoring flammable gas in safety related applications the
ULTIMA XIR must be calibrated with a known concentration of the gas
being monitored.
(1) Relative response factor for Methanol from the ta-
ble in this chapter
= 0.70
(2) Propane calibration gas concentration being used = 0.89 Vol% C
3
H
8
(3) Propane volume concentration for 100 % LEL = 1.7 Vol%
(4) Propane calibration gas concentration in % LEL
% LEL = 0.89 Vol% C
3
H
8
x
100 % LEL
= 52.4 % LEL
1.7 Vol% C
3
H
8
(5) Gas calibration set point = 52.4 % LEL x 0.70 = 36.7 % LEL
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