Black stains on an indoor ceiling (C) Daniel FriedmanOil Burner Puffback FAQs
Q&A on the cause & prevention of puffback explosions

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Oil Burner Puffback questions & answers:

Frequently-asked questions & answers about the cause, cure, and prevention of oil burner puffback explosions that can blow soot and oil burner fumes throughout a building.

Oil burners, used on heating furnaces, boilers, water heaters, calorifiers, cylinders, or other heating appliances can, improperly serviced or adjusted, cause puffbacks that can be dangerous, as well as expensive.

This article explains the cause, cure, and prevention of potentially dangerous and sooty oil fired heating equipment puffbacks that can occur at an oil fired boiler, furnace, or water heater.

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FAQs on Sooty Puffbacks at Oil-Fired Heating Equipment

Black stains on an indoor ceiling (C) Daniel Friedman

In this article series we explain oil burner or oil heating system puffbacks: what happens, and what causes them.

Watch out: if the reset button on your heating equipment has popped, you might press it ONCE to see if the equipment will run and provide heat (or hot water) while you wait for repair service.

But do not keep pressing the button repeatedly as doing so, particluarly if the burner does not run for 10 minutes or more, risks a dangerous puffback explosion when un-burned fuel in the heater finally ignites - causing a puffback explosion.

At AQUASTAT RESET BUTTON we list the location of all of the various reset buttons and controls found on heating equipment.

Questions & answers about oil burner puffbacks & puffback explosions posted originally at OIL BURNER SOOT & PUFFBACKS

On 2017-04-08 18:28:25.295270 by (mod) re: dangers of chimney leaks into a building structure are serious


If a heating system chimney is leaking anything - including exhaust or fumes - into the building, the chimney and heating system are unsafe, risking fire and (particularly when gas fired equipment is being vented into a flue) fatal carbon monoxide poisoning.

I can't diagnose your situation by e-text but from what you describe there are serious, possibly fatal safety hazards in the building - the management, occupants, etc. need to know that immediately.

On 2017-04-08 15:59:47.594018 by john niemela

My Super,Last Summer Fired Up The Boiler,My Sisters Apartment is on the 5 th floor,She Has Holes in Her Ceiling,The Entire Apartment,was Filled with Boiler Fumes,Now,The Fumes shoot out of the chimney,before this genius,the fumes were 1 ft above the chimney,now,they re 10 feet in the air,Did something go on the 5 th floor as far as the chimney,a plate or something else?

On 2017-03-30 19:14:53.837192 by (mod) re: turn off unsafe heating equipment immediately


LEAVE THE BOILER OFF right away to avoid a puffback explosion.

Most-likely the automatic oil line shutoff valve/check valve in your fuel unit (oil burner pump) is sticking open. Sometimes we make a temp fix by adding an oil delay/stop valve on the line between the fuel unit and the burner nozzle oil line inlet.

On 2017-03-30 19:10:31.044019 by Gary

Why is there oil going into the boiler when the oil is turned off . When turned back on it sending out a lot of smoke and smell

On 2017-01-20 04:27:57.085894 by Isaac

We have a oil burning furnace with two large tanks in the basement. We randomly hear a very loud bang coming from the tanks of furnace when the system is not running. I see no signs of a puffback. Do you know what this could be?

On 2016-12-17 by (mod) re: obtaining outdoor air supply for an oil burner

You can certainly obtain an outside air supply for the oil burner - as some systems provide a duct that brings outdoor air to an enclosure around the oil burner. You need about 1 of un-screened air intake opening per 1000 BTUH.

On 2016-12-17 by K Purcell

I have an oil-heated hot water tank. We have a workshop in the basement and dust gets into the burner. My oil-heated furnace has a metal cover over its burner. Can I get or make a cover for the burner for my oil-heated hot water tank? It is a Brock.

On 2016-11-28 by Joe

I have a bekett furnace and I get a big puff back the chimney I pipe is clean and the flame looks good the furnace starts good and shut off ok but sometimes I get a bang in the furnace and it blows the damper off the pipe.

On 2016-02-01 by Joe from Brooklyn


On 2015-12-01 by (mod) re: inadequate combustion air causes smoky oil burner flame

Good going, Rob; indeed inadequate combustion air will give us a smoky flame; at this point a worry remains that the nozzle assembly is sooty and dirty; keep an eye on how the system is running.

On 2015-11-30 by Rob

found the air intake was packed with lint and dust. looks like it was never cleaned.
cleaned it out and reset the air
everything seams to be going well...time will tell
thanks for the reply

On 2015-11-30 by Rob

also getting allot of black smoke from my chimney

On 2015-11-30 by (mod)

Perhaps your system has an air leak in the oil piping

On 2015-11-30 by Rob

I just cleaned my boiler chamber and removed jacket and cleaned sections and chimney base. Also replaced the filter, nozzle and electrodes just because I was in there and they looked a little caked up. Everything appeared to be running great but now I am getting a tiny puff back on ignition. I have no leaks so I don't think any air is trapped and I have good draft so no blockage in chimney.
Any ideas on what could be causing this?

Question: Help with an oil-flooded water heater that caught fire

I have a oil fed hot water heater, the primary ignition relay malfunctioned , causing the hot water heater to have excessive amount of fuel inside furnace chamber.

I cleaned as much of it. replaced the primary ignition ,When restarted the hot water heater spews dark gray smoke from chimney, also noticed when I shut hot water heater off,

I ck'd access hole to furnace(hot water) there was a fire inside. I put out fire with water. I need help - Matt

Reply: flooding the water heater ignited unburned heating oil and risked a "puffback" - clean or R&R oil-soaked combustion chambers before re-igniting the burner

Matt, fresh out of oil burner school we were always terrified about lighting off an oil burner into a previously flooded combustion chamber and flat wouldn't do it if we hadn't cleaned the system and even removed/replaced oil-soaked combustion chamber liners. And if the chimney was of unknown condition we'd have it inspected (Chimscan, the works) - even so, it was not unusual to call the fire department and have them on stand-by: that's what we were taught to do.

The first time I called the fire department to ask them to go on stand by while we fired up the boiler, the fire department operator said "maybe you should get someone in there who knows what they're doing" - which didn't inspire much confidence.

Now that you've had a fire you really cannot safely turn the equipment back on before an expert inspects the chimney and flue for safety;

A modest oil residue in the combustion chamber can be burned off. But a really flooded chamber deserved to be disassembled and cleaned or replaced.

Question: soot blamed on power vent and chimney, reappears after clean-up

(Dec 5, 2014) Amy said:
I had a problem this past spring with black soot throughout my home. We had 2 different companies plus a mechanical engineer come in to determine that the furnace was fine and that the cause of the black soot in the house was from the power vent. We got the house cleaned by a fire cleanup services company and all the rooms were painted because they couldn't get the soot all out. We replaced the power vent with a chimney.

I am beside myself that I have again found the black soot coating white plastic containers in my kitchen cupboards. I have contacted a materials lab and was told that I would need a good amount of the soot in order for them to test it. This could take a very long time to collect because it's a black film that smears. I don't know what else to do or who to turn to for help. I can't go through what we did this past spring. Do you have any thoughts and or recommendations as to what I can do? Thank you for your time!


Sorry to read about this soot Amy - perhaps the original diagnosis was erroneous. After all, a sooting-up oil fired heating system can clog a power vent just as it can clog a flue vent connector, heat exchanger, or chimney.

You need help from a trained and experienced heating service tech.

Let me know what you're told.

Question: diagnose oil smell in a NYC Building with Gas boilers but oil burner next-door

(Feb 21, 2015) Landlord said:
Is it possible for a malfunctioning oil furnace to be the cause of an oily smell in an adjacent building that has gas boilers? I own a brownstone with four apartments. The building has four gas boilers but the attached brownstone next door has an oil furnace. There is a smell of oil particularly in the ground floor apartment that is worse on very cold days. The smell began with the very cold weather about six weeks ago. The fire department and gas company have ruled out a gas leak and the boilers have been inspected.There is also a smoky looking streak on a wall where
a wall and floor come together but it is not on a wall adjacent to the building with oil heat. The smell has been described as oily, a chemical electrical smell, and a burned out candle smell. Any advice would be greatly appreciated.



It's a fair question but not one that I think we can diagnose from just an e text. A thoughtful onsite inspection may help. Start at the oil storage and piping system, oil burner operation, and possible fuel or fours gas pathways.

(Feb 24, 2015) Landlord said:
Thank you for your response. Given that I do not own the oil furnace in question or have ready access to it, an inspection is not easy to do currently. The question now is this: given the information in the first message, is there enough evidence to inform the neighbor with the oil furnace that the furnace may need attention? Could there be a danger to my tenants from this oil furnace? If so, Is there a city/ government agency (in NYC) that follows up on a situation like this? Thank you for any advice you can offer.



I really would like to help but with no actual information about the property I can't buy enough liability insurance (don't have any at all) to bet your safety or that of others by speculating when I am flying so blind.

It's fair to say that if there are gas odors in a building most people can identify that accurately as the odorants in natural gas or LP gas are rather recognizable - and that'd be enough to raise a safety concern. You say there have already been expert inspections, leaving me confounded.

NYC agencies involved include the fire department, building department, and the NYC Housing Department

Question: is a puffback dangerous to your health?

(Mar 17, 2015) Joan Thorson said:
We had a puffback in our home is this dangerous to our health? Ins. co being notified.


Joan it's a fair question to ask but not one that can be assessed by an e-text. Sure, breathing oil burner soot is potentially hazardous - it depends on the dose and exposure duration as well as individual health and vulnerability. If you or any occupants have reason to feel concerned I'd check with the family doctor first.



And of course any explosion can be quite dangerous.


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