A carbon dioxide monitor in our house, but we all carry a sensor called a nose and you know if you are in a space that smells fresh or if it is stuffy and it is a good last result centre and we should be using it rather more than perhaps we do. i am using it rather more than perhaps we do. iam not using it rather more than perhaps we do. i am not suggesting we have a howling gale blowing through the dining room and spoiling a christmas dinner. i am suggesting however that we crack as many windows open, high—level ones in particular, because you won't get a cold draft as easily with high wind...