I hope everyone's Yuletide preparations are going well! I have a handful of seasonal items to talk about: The ghosts of parties past, candles, and theYule gas log.

In the last year or two, the IAQ (indoor-air quality) industry has taken an interest in candles. It seems that all candles produce some amount of soot, and some of the newer 'liquid' candles produce quite a lot of it. You usually don't see the soot, but if you burn a lot of candles, it will start showing up in suprising places.

The inner surfaces of outside walls and ceilings of your home are cooler than the inside walls. That just makes sense, because no insulation is perfect, and heat is always being conducted from inside to out. (at least in winter). Most people aren't aware that the temperature of an outside wall is not even, but has cool and cooler spots. The cooler areas are where the drywall or plaster is in contact with a structural member, which is also in contact with the outside surface, or with the cold air in the attic. The less cool areas are in contact with the insulation. So how does this relate to ghosts? Let's go one more step.

The air in the house carries a certain amount of water vapor. At times (shower time, pasta cooking time, laundry time) there can be several gallons of water in the house air. When this vapor finds a cool spot, it condenses. Usually, there's not enough to see, no droplets or even mildew, but the cooler spots on the wall will be slightly damp for a while. Now, imagine microscopic particles of soot, too small to settle to the floor, just drifting around on the air currents. Where are they likely to stick? That's right, on the damp spots. Which are the cooler spots. Which are often straight lines, because they are along structural members. So you get a "ghost image" of your house's framing showing on the wall or ceiling.

Our great-grandmothers spent a lot more time washing walls than we do. They were heating with coal, oil, or wood, and the air was full of soot all the time. After a couple of generations of heating with natural gas, we have forgotten about this. So we bring in candles, and get mystified by the sooty ghosts that appear on the walls!

What if you have ghosts, and you don't burn candles? Think about other sources of floating carbon particles. A fireplace that doesn't draft well? How about a gas range that runs rich and acrid? Another possible source is a dangerously bad furnace, running rich, with a cracked heat exchanger. This will leave ghosts at the heat registers, especially on carpet. Remember, soot is often accompanied by carbon monoxide. If you have ghosts and just can't find any source, have your furnace and gas range professionally checked. And don't idle that Vovlo diesel in the garage!

One more ghost maker: gas fireplaces. These things are often sooty, because the yellow flames that make the fire look pretty are rich, dirty burns. A lean, clean burn produces a plain blue flame, and how romantic is that? ("A lean, clean burn, for a plain blue flame"..By George, Pickering, I think he's got it!) Of course, you open the damper whenever you have a fire going, so it all vents up the chimney, right? What about that pilot flame in the gas log set? If the pilot is on all the time, the damper has to be partly open all the time. The damper should have a little metal clip on one edge to keep it from closing all the way. Check yours, if you keep a standing pilot in the fireplace. (Or invite him in to sit down!) If you light the fire manually each time, or if it has some kind of electric spark igniter, this isn't a concern.

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In the literature: During some of my home inspections, I find rotten wood in trim items such as window frames and porch columns. Of course, I always recommend replacing the damaged wood if practical, but sometimes replacement would involve major surgery. In those cases, I recommend repair with epoxy compounds. My favorite has always been Git-Rot, but that's probably a prejudice from my days as a WoodenBoat devotee. There are now other epoxy repair products that are designed for use on shore. The December issue of The Family Handyman has a great how-to article on repairing and rebuilding wood with epoxy.

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Nag-of-the-Month: Yes, many of us use extension cords for Christmas tree lights. It's not the safest practice, but the worst part is burying the cords under fabric tree skirts, rugs or carpet. That's a fire waiting to happen, so keep your extension cords visible,and your fires in the fireplace. And double-check all smoke alarms before the holidays!

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In any event, we at Sherlock wish you all a very Merry Christmas. God bless us, every one!