The military smoke screen was first used on this day in 1923 in a test off Cape Hatteras. It was undertaken to conceal ship and troop movements from enemy eyes. For land and sea battles, it works well. But in your own house, you want to avoid a smoke screen. Firing up the fireplace after it's been sitting all summer after last winter's use, can cause all sorts of unwanted problems. They range from red eyes and coughing to air pollution and carbon-monoxide poisoning. So, before you hold a match to any logs, be they natural wood, or natural gas, the Chimney Safety Institute of America urges homeowners to check flues and dampers for any blockage, debris or creosote buildup. This can be done by the homeowner or by a chimney pro (chimney sweep). This will ensure that everything is free and clear and totally ship-shape. Otherwise, you could be in for a military-quality smoke screen of your very own ? with explosive action and real live firemen. And that's the On The House tip for today.