To hold either a round or square post plumb inside a post hole while you pack dirt around it, make up a couple of wedges of 2x6 about 30 in. long. Cut to length, then make an angled cut from a corner of one end to the center of the other end. Insert a wedge on each side of the post; they will adjust in the hole for either post size or hole size.
Gas logs release a lot of water vapor when they are burning. You should be wary of mold and mildew, especially if you have asthma and respiratory problems, when using them for longer than a few hours. A CO detector is a great gas-log accessory. You can find one in many home-improvement and mass chain stores