Somebody has said there is a smell like fish oil coming from her hot press (not sure if the term 'hot press' is used worldwide: the airing cupboard / the cupboard with the hot water tank in).
Her house doesn't have mains gas.
She's checked for anything visible that it could be -- no fish oil tablets in pockets of clothes; nothing like that.
What might this be?
And how might this be dealt with?
(Firstly, I want to check that it's not likely to be some kind of poisonous gas or something. And secondly whatever it is, to try and sort it, to improve the space -- so she can use the cupboard.)