I never iron sheets or duvet covers, but I have ironed pillowcases and hankies since I went on a Red Cross First Aid Course in the 70s, and the instructor told us that the only practical treatment for burns in the home was lots of cold water, then either cover with a clean, ironed hankie or, if the burn covered a whole limb, put it (the limb) inside a clean, ironed (and therefore sterile) pillowcase for the journey to hospital - he went on to say that this was practical because it could be found in every home. Judging by the expressions on the faces of the female pupils (including me) I'd say he was wrong there, but I've tried to do it ever since.