I plan to install venting from an existing cooker hood using flexible aluminum ducting (4" diameter).

Does this need 'earthing' in any way ?

If so, is this in terms of connecting it electrically to the earthed body of the cooker hood, or directly to the earth in the CU.  How do you make the connections to the aluminum duct sections ?

The hood is an electrical appliance - it is made as a single item (ducting excepted) with lights and/or fan, and an electrical connection.

If it has an earth connection, it will be earthed automatically and appropriately when it is plugged/wired in.

If it does not, then surely by "bonding" the hood to the earth terminal of the cooker you are earthing the casing of a Class II appliance - something not recommended?

Thanks for the replies.

I suppose what I was thinking of was the general thing of earth bonding metallic items such as gas and water piping ... is there something which distinguishes this from the vent ducting ?  (I think the cooker hood itself is a bit of a red herring).