Hmmmmm..... the third prong on the vacuum is the 'ground' wire, which connects the appliance directly to the earth. The ground wire minimizes the risk of electric shock if a fault in the wiring causes current leakage through an uninsulated bit of the vacuum. If you plug it into a 2 prong extension the leaked current doesn't have a direct path to earth, other than through you! Never a good thing! Especially if you are standing or kneeling in moisture. In those circumstances you can easily get a fatal shock without tripping fuses, or even sensitive GFI units.
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Hmmmmm..... the third prong on the vacuum is the 'ground' wire, which connects the appliance directly to the earth. The ground wire minimizes the risk of electric shock if a fault in the wiring causes current leakage through an uninsulated bit of the vacuum. If you plug it into a 2 prong extension the leaked current doesn't have a direct path to earth, other than through you! Never a good thing! Especially if you are standing or kneeling in moisture. In those circumstances you can easily get a fatal shock without tripping fuses, or even sensitive GFI units.