I have long been a proponent of banking coals under ash when it is too warm to put on more wood but you know in the next few hours you are going to want to start a fire. And it also keeps a stove and flue warm for a long time. Well, not anymore. Today has been in the forties and raining all day and the house was at a comfortable temp so I banked the coals from the morning fire after noon for a late afternoon restart. Later I did a good bit of cooking in the microwave oven that is across the house in the kitchen which for all intents and purposes is one room with the family/stove room. A little before I was ready to uncover the coals and restart the fire I walked past the Kidde Nighthawk CO detector over the kitchen counter top and, as I do often, hit the button for the highest stored reading since the unit had been reset. I have never seen anything other than "0" displayed. This time it showed a reading of 20 parts per million. Not a dangerous level or one that would set off the alarm but I wasn't happy to see anything but zero. I went over to the stove and uncovered the coals and put some small pieces on to get the fire going in the warm stove. And had a heck of a time getting a draft going. I am convinced that I know what happened. The coals were sitting there under the ashes giving off CO which was supposed to be going up the chimney. But between the high pressure right over us with the rain and that microwave oven, which happens also to be the range hood, running there was a flue reversal and the hood was sucking CO out of the stove inlets. The draft is back up to speed and no new CO has been detected but I just wanted to tell you folks that I no longer recommend something I have done for years. Banking coals in a wood stove. And shiver a little when I think about how many times I have done it and then gone to bed for the night.