If you are getting soot in the house, it can be caused by several things. A blocked flue passage(s) between the combustion chamber and the breach, blocked chimney, improper air setting on the burner, or a dirty nozzle end.

These are some of the major causes and it can be one of them or a combination of more than one. You also need a hole somewhere in the flue or furnace heat exchanger to let the soot out.

Carbon monoxide is not a major problem with oil heat because you'll probably be drive out of the house from the smell before CO gets you.

If you have no odor, you probably have a small amount of soot leaking out and it takes 8 months to build up around the house.

Have someone check for a bad heat exchanger, in combination with the first paragraph's possible causes.

Hollan,
I was having the same problem when i first bought my house.
Curtains were black around the registers by the end of the winter. After the unit was thoroughly cleaned and the nozzle changed, it subsided drastically but i think oil is just a dirty fuel and soot can't ever be eliminated 100%, especially with hot air heat. Because my unit was older and because the utility company was giving a rebate I converted to gas heat last September. I know its not an option if you do not have gas lines in your area, but if you do its worth consideration. The new gas furnace is 75% quieter, smaller, no more tank in the basement and there is no soot anymore.

Yes the soot in your house is from your furnace!
While it is true that an oil furnace can be set up properly, the number of mechanics that know how or will take the time to are dwindling. More than likely, barring a hole in the heat exchanger or poor draft due to a partially plugged chimney, if your furnace has been cleaned, the combustion is incomplete or ignition is delayed due to improper adjustments. Check around the smoke pipe to the chimney especially around the barometric control (the floppy, flippy damper like thing on the smoke pipe) Soot exiting there is an indication, usually of delayed and incomplete combustion. A partially plugged nozzle, cracked or out of adjustment electrodes, a broken or deformed firing head, misset nozzle assembly, a fuel/air mixture that is too rich or too lean can all be causes of this. When asking for a service man make sure he is familiar with oil furnace service and tell them of the chronic misery you've been experiencing. That alone will scare those unfamiliar away. Even if there is not a LOT of soot evident near the furnace or laying around, a little soot goes a long way when it's air borne and distributed through your house via the duct system. If gas is near you - go for it! Contrary to many fine people who stand on the benefits of oil heat ..... it's an antique. It was designed for houses that the wind blew through.

Any dirt produced from any type of fuel should stay inside the furnace and vent to the outside. If you are getting dirt inside the home it is getting out of the heat exchanger or vent pipe somehow. First make sure the unit is set up with a combustion analyzer and have the contractor do a heat exchanger inspection. Verify there is enough combustion air.

Here is a link that might be useful: Comfort-Calc - Combustion Air Calculation

Thanks for all the information. It's true that it is very hard to find people to service oil furnaces. The man that cleaned ours said the black was because it was so dirty and it would go away. Later in the season, I asked him to come check why it sounded like it was turning on and off several times while the blower stayed on, but he would never come back.

Gas is available in our area. If someone has recently converted from oil to gas, I would be curious to know how the price of heating compares. Actually, it would be worth more to not have soot in my lungs.

HereÂs a Âround about idea of comparative prices - fuel oil vs. natural gas - from a gas bill that I dug up from 2008.

For 9 CCF of natural gas I paid (including delivery charges and taxes and blah, blah, blah) - $14.54
That does NOT include the "availability charge" that I pay for the stupid meter hanging on my building, but itÂs a commercial account.
But eliminating that, it comes out to about $1.61 per CCF. (CCF = approximately 100,000 btu)
Right now that same amount of gas would cost me approximately $17.56 or about $1.95 per CCF
WeÂll go with that.
A gallon of #2 fuel oil right now, looking around, IÂm finding to be about $2.49 per gallon for my area, which is northern Michigan.
I donÂt use fuel oil so had to search it.
Fuel oil will give you about a 38% bigger bang per gallon as opposed to a CCF of natural gas.
So then, to end up with that same BTU content I would have had to spend $2.69 per CCF.
However, if my oil furnace were running at AT BEST 70% efficiency ( which unless yours is a fairly recent model IÂm guessing it isnÂt) things change.
But letÂs give it the benefit of a doubt and say it, as it is, is running at 75%.
That would mean that you are getting usable heat with oil worth about $1.86 per gallon
A natural gas furnace running at 95% efficiency will give you that same usable heat for about the same amount -
$ 1.85
Lower the efficiency of your oil furnace, which IÂd be willing to bet realistically isnÂt much better than 68%, and things change again of course. Now for every $2.49 youÂre spending youÂre getting about a $1.69 worth of usable heat. A nearly 10% difference on the down side from natural gas.
Higher efficiency oil furnaces are out there which would save you money and you may be able to up that oil efficiency to 80 or 85%. Then youÂre going the other way. BUT - keep in mind, once again youÂre dealing with a fuel that few are conscientious enough to service properly, has more variables in terms of things going wrong and, like it or not , in my opinion will always give you that olfactory reminder that itÂs in your house.
ThatÂs for now. But if our government and this current whacked out administration has itÂs way weÂll all be paying a fortune to keep our butts warm anyway according to our "carbon footprint". Relative to which yours may be larger. To spare you my opinion on that and to keep my blood pressure down, I'll stop right there!
Hope that was some usefull information.

Snoring cow, I think you should go back to sleep. Your obvious bias against fuel oil and the ridiculous comments about it are just over the top.

Fuel oil and natural gas are competitive. Sometimes they are out of whack but they are pretty close. According to the Penn State calculator, their chart uses 80% efficiency for fuel oil and 85% efficiency for natural gas to compare the fuels. If oil is currently $2.49 a gallon, then it's the equivalent to buying gas at $1.90 a therm (100,000 BTU.)

Anybody in the business knows that oil is now producing over 90% in a condensing boiler system and in the mid 80s in a furnace. Gas is also producing over 90% in a condensing system.

The OP seems to have a leak in the heat exchanger and the second poster does not. Blackness on the curtains near the register is from dirt in the air, not a leaky furnace. In that case, there would be blackness everywhere in the house and also the smell of "diesel fumes".

If a new system was in order, and natural gas was nearby, I would consider gas. If a new system was NOT in order and considering the lengthy payback based on oil to gas savings, I would not NOT switch until my furnace was shot. Many rural people have no choice in the matter as there is no gas.

To state that oil is an antique and designed for houses that the wind blew through is just a patently ridiculous statement.

Are you burning candles or any of those oil lamps?? I've seen it. Especially w/ the cheaper candles. Just something else to cross off the list.

Baymee -
Yawn, I just woke up! Thanks for the rebuttal. If you'd have read my post apart from maybe your bias against other posters - you'd have seen that I did state that they are comparable. In fact, you'd have seen that I stated quite clearly that a high efficiency oil furnace in good repair and well maintained would actually save money, albeit my question is and will always be - is it worth it.
Been out here bumping into oil furnaces installed by every Tom Dick and Harry for 32 years. Followed up by people who change a nozzle and walk away thinking they fixed something. Half of what I've run into isn't installed properly from the get go, chimneys that won't draw, barometric controls that are apparently just for decoration, oil line systems and tanks that are a joke, and by now most of them are 50 yrs old. Fortunate if you can even find an oil filter on some of them. They all have a pile of six to ten old nozzle laying next to the burner, and a healthy oil stain on a saturated floor out 2 ft. in front of the furnace.
Sure a well maintained high efficiency oil furnace can be satisfactory. And if a dealer/installer is willing to back up his installation with the know how that's just dandy.
If I'm out of touch with the latest in oil heat technology it's because I will not sell them unless a customer demands it or it is a last resort. I would just simply never recommend such a headache to a customer if there were another way. And we are talking, I believe, about a forced air oil furnace here, not a boiler. Although I'm acquainted with those from back in the day as well. More than a few times I came in ahead of a clean-up crew that had to clean an entire house. Yes! I'm biased in favor of an alternative to fuel oil. You betcha. And last I checked - I can be.
And I don't know what kind of dust you have in your home, but the dust in mine is not BLACK, on the curtains, windows or elsewhere. But maybe you have an oil furnace.
I don't do argumentative forum stuff, if that's your game. If I have a difference of opinion it's generally directed and with respect to someone elses. So this will be the end of this.
Have a great day!

Hollan,
doug199 makes a very good point. I once had a call back on a gas system I installed blamed for soot throughout the house. Turned out that's exactly what had occured. The homeowner burned candles quite frequently.
And my apologies if my habit of interjecting a bit of candor into my posts may have been offensive. My comment suggesting that fuel oil was an antique and designed for houses that the wind blew through apparently offended someone. But many of the houses that I run into with the old girls in them are nearly exactly that, old farm or village houses built back in the day when a gallon of fuel lost up the chimney was no big deal. My only point is, if you have an old oil furnace it is probably less than efficient by today's standards. If it's giving you problems it's probably also costing you money, has served it's purpose and it may be a good idea to think about moving on. Perhaps I should have asked you more questions rather than to go on assumptions.
Good luck with whatever you do!

I'm still here, unoffended, apparently not catching on to candor.