You are right - and I know the rules. But these are very weird, one day yes and two days no, no matter how much I use a vacuum cleaner. I use a special "duvet" made of pure sheep wool, my daughter bought this and a pillow in a special producer, it is anti-allergic. But I suspect that I miss sleeping with my balcony door open, or at least a window open. I never have a heating on. Unfortunately opening anything is out od the question in severe freezing these days.