| Exception: | Where a mortar is to be used only once, such as for an electrically fired display, added support shall be optional and shall not be required. |
| Exception: | Where electrical ignition of unchained aerial shells six inches and less in diameter is used, there is no requirement for separation of mortars. |
| Exception: | Where electrical ignition is used, all mortars placed in drums or troughs shall be spaced at least two inches from the wall of the drum or trough. |