ICC EXCEL Installation And Maintenance Instructions Manual page 9

NOTE: Excel is required to be enclosed (framed in) when it passes
through an occupied area in the building. In the event that Excel passes
through an unoccupied area and is not enclosed it should be installed with
ERS radiation shields instead of ERSA radiation shields. If the chimney is
not enclosed then the ERST of ERSF radiation shields are not required.
See drawing above.
Please note that Excel may be used to vent a factory built fireplace,
an oil burning appliance, or a gas burning appliance. The ERSF or
ERST radiation shield tubes are not required when venting these
appliances, even when the chimney is enclosed.
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EXCEL Canada Owner's Manual