Smoke smell in house with oil boiler

At this point I detect the odor in all of the downstairs rooms at various times, and also upstairs. Upstairs I "think" it's mainly when the furnace is running.

The strategy I'm using currently is to turn the thermostat down to 50 overnight so the furnace doesn't come on very often. In the morning I turn it up to 60. When the temperature in the house hits 60 I turn it down a couple of degrees. After awhile the smoke smell dissipates and then I have a few hours of decent air quality. I also open a window in the basement during the day and close it at night.

I'm thinking that the variations in the smell and the smell suddenly starting when the furnace isn't even running is due to changes in pressure in the chimney according to the weather and wind and residual odors in the chimney when the furnace is off. It does seem better when it's warmer outside.

I recently spent several hours in the garage, which is connected to the basement by an open doorway and other air passages, and the smell wasn't present even when the furnace was running. I don't really smell it in the vicinity of the furnace either.

I haven't had the damper installed yet. We've been getting snow several times a week here and I've had to shift my attention to snow removal.

I don't foresee getting a chimney liner until spring, if I go that route. I have wood ready to burn if the problem gets worse. I'll see if the air purifier helps in my small office.

Well, it's been 3 weeks since you flossed but you don't see me pointing that out publicly because I can imagine so many reasons why you've neglected that life-saving task. Fun exercise for you: list 10 reasons why someone in a major snow zone would be slow to get a damper installed. Floss first, though.

When I first detected the smoke smell I immediately had the fire department check the house for CO. None at all was present. I have CO detectors on all three levels.

HVACNUT, can you say more about this?: "You have a positive pressure boiler without a draft regulator."

According to google AI, "A 'positive pressure oil furnace' refers to an oil furnace that creates a slightly higher air pressure inside the combustion chamber than the surrounding environment, essentially pushing the flue gases out of the chimney; while most positive pressure oil furnaces do not require a barometric damper because they already have a controlled positive pressure, it's always best to consult the manufacturer's instructions as some situations may still necessitate one depending on the specific design and chimney configuration. A barometric damper is . . . typically used on furnaces with negative pressure venting systems to prevent backdrafting. . . . In some cases, even with a positive pressure furnace, a barometric damper might be recommended if the chimney design is particularly problematic or if there are significant fluctuations in outside air pressure."

From google AI's original source: "Barometric dampers are installed only on boilers with negative venting. Boilers with pressurized vents would spill flue gases out of the barometric dampers into the room." https://www.pmmag.com/articles/105790-the-misunderstood-barometric-damper#:~:text=Barometric%20dampers%20are%20installed%20only%20on%20boilers,of%20the%20barometric%20dampers%20into%20the%20room.

I found the installation instructions for the Smith 8 series oil burner:

"The 8 Series boiler-burner unit . . . is rated for natural draft firing with -0.02" W.C. over the fire draft."

"For energy conservation, the boiler can be vented directly into a chimney without the use of a barometric draft control, unless required by code or in instances where the chimney can develop excessive draft. Overfire draft greater than -0.05" WC, with the burner in operation, is excessive (normal draft is -0.02 to -0.04" WC) ."

On the printout from the technician the draft was -0.188 mbar. Apparently that's .075 water column inches. EdTheHeaterMan also stated previously, "That would translate to about -.0.05" wc over the fire. I believe that HB Smith recommends no more than -0.01" wc over the fire for efficient operation. Did they take an over fire draft?"

I don't know the answer to that question, but from Ed's calculation of -.05" wc over the fire, it seems that the draft is just barely higher than Smith's maximum spec.

Q1: If smoke is being drawn from the chimney into the basement—I have now confirmed that this is the case, contrary to what I said earlier—doesn't that indicate low draft, rather than high?

Q2: In that case, how can a barometric damper help?

Q3: I think y'all are saying that regardless of the manufacturer's specs and test results, this is a problem situation where a damper should be installed. Is that correct?

A couple of details I didn't mention earlier. The house is on a slope with pine trees over 100' very close to the rear of the house. The chimney is located on the back of the house. The prevailing wind of the south-facing house is toward the front of the house. Two things have changed in recent years: (1) Much more frequent wind storms with higher winds. (2) One of those tall pines fell, opening up a space. I don't know if either of those things is relevant.

What do those do, please?

OK, I made an appointment to get the damper installed next week. I'm probably going to start heating with wood until then.