Hi .do you have a real fire in your house that could be giving off soot?
Any smokers in the house?
Hi , it will be dust that circulates and then rises with the heat of the radiator. If you have your heating on constantly without windows open this can cause it too. It shouldn't be a concern . the only concern would be if it was soot from the boiler due to incomplete combustion . I'm sure the gas service guy checked for this , but you could always buy a carbon monoxide alarm for safety / peace of mind
I don't know what are you expecting . do you have your heating on constantly without windows open?
I have seen it many times . it is usually in homes where the heating is on nearly all the time and it is both ng too worry about . the only solution that I can think of that might help is to fit radiator covers which would disperse the hot air in front more and stop it running straight up the back wall . good luck , all the best with it
Thanks . I only tried to help you . is that bad?. Maybe you wanted to hear something bad, but there is nothing wrong