In general, the answer is No! The HOTTAP must be used outdoors and in a well-ventilated area.
This applies to houses, sheds, shacks, camper trailers, caravans, houseboats, bus and van conversions, etc. You might want to check on the specific compliance requirements of your vehicle but we always recommend to use the HOTTAP outside.
If you need to get hot water inside, to an existing sink or something like that, this is still perfectly possible (and quick common amongst our customers) by setting up the HOTTAP outside the vehicle and quick connecting the hoses to your internal water lines.