Earlier this year, the Health and Safety Executive issued a Safety Alert about Welding Fume: http://www.hse.gov.uk/welding/fume-welding.htm
The key message is that
So if you're welding at home, without sufficient ventilation, make sure you're wearing a suitable mask.New evidence shows exposure to mild steel welding fume can cause cancer.
The current guidance on mild steel welding is out of date and will be updated as soon as possible to take account of this new evidence.
If you think you're too old to worry about it, consider those about you that might have a lot longer to be affected, perhaps children or grandchildren.
If you think 'The smokes gone, it's safe', think again.
The smallest, most dangerous, metal fume particles that will get into your lungs are only visible with an electron microscope and recent research has shown that they can remain suspended in still air for up to 41 hours. If something is 'Inhaleable', you can breath it in, but also out again; if something is 'Respirable' it is small enough to get right into the smallest passageways of your lungs and won't come out. I'm not posting this up to generate some "Elfn'Safety" debate, just highlighting it for people's information, so they can make an informed choice.