No, it isn't normal. It's normal to get a bit smelly on your hands if you are putting logs on it but otherwise all fumes should be going up the flue. How long have they had it? Was it fitted by a professional? When did they last get their chimney swept?
No that doesn't sound normal. How long have they had it? Was it installed by a qualified Hetas engineer? Do they have a certificate for it? We had to have the chimney specially lined for ours and the flue carries all the smoke away - there is no soot or smell. I would check out how the installation was carried out if I were you.
That will be because the flue isn't drawing enough. Mine draws the smoke up the chimmney even with the door open but if they have to leave it open all the time then it's not working properly - the flue could be blocked or installed incorrectly.
If your dad fitted it and he is not a hetas certified engineer then the local Building Inspector would check it for a small fee. It is a legal requirement to comply with building regulations and you shouldn't take risks with carbon monoxide...
they need to stop using it AT ONCE. Woodburners should never be used with the door open - you put the wood on and close up. There may be a bit of a smell with certain wood but certainly no black on the ceiling. Sounds like an installation foul up, a blocked chimney, a failed seal or something else WRONG.
Unless you dad has a HETAS certificate (and if he has, shame on him) they have invalidated their house insurance with this. But they are at reasonable risk of death RIGHT NOW. The black on the ceiling means incomplete combustion which produces carbon monoxide.
I thought you could use them with the door open. Ours came with a special grill for when you wish to use with the doors open. We sometimes have our doors open a bit to get it going. Only been in a year and was installed by HETAS.
There's something wrong with theirs OP, We've had one for 19 years and never had any soot on the ceiling and no one smells like a bonfire, you'd never know we had it. We have on occasion when it got really hot had the door open, as it draws air just fine all it did was make the wood burn faster.
as everyone has said, it is not normal and it is not safe. The black marks are soot stains. There is a leak somewhere in the stove or the flue, and/or the chimney is not drawing properly. Even with the doors open, it should suck all the POCs up the chimney, there should be no airflow possible INTO the room. It is possible that the room does not have sufficient natural ventilation to let fresh air into the room to allow airflow up the chimbney. Some people like to block ventilation because they consider it to be a draught.
If your dad is as pig-headed as me, though, he may resist suggestions that he has cocked up and put his family at risk.
You could start by getting an experienced local chimney-sweep to look at it, he will be familiar with all the common defects.