Smoke Abatement Solution

[knormie]

My neighbor complained about the smoke from my WFO. I probably would have done the same in his shoes. Bribes of baked goods were ineffectual so I was forced to find a way to reduce the amount of smoke emitted by my oven, particularly during the first 60 min of warm up. I searched the internet and explored wood fired oven and baking forums but could not find a proven, residential solution.

Commercial systems use water to knock the smoke out of the exhaust, so I decided to emulate these in a scaled down fashion. My design uses the parts listed below to construct a mister on a stick that I can insert into the top of the chimney just beneath the rain cap. The first test was extremely encouraging. The WFO produced a small fraction of the smoke that it usually does, no more than 10% of the normal amount, perhaps less. The smoke that did escape dissipated very quickly and was invisible just over the fence line - about 10-15 feet.

During usage, the exhaust maintained a positive draw and the measured exhaust temperature did not exceed 200F. A metal tub was positioned beneath the chimney on the landing to catch any drips and drops that ran down the inside of the chimney, This is a .5 GPH nozzle so very little water reaches the bottom and once the tub heats up, it boils off any drops that reach it so there is no sooty water to deal with.

I ran the mister for about an hour and disconnected it just before the last bit of soot had burned off the dome. I?m very excited about these results and look forward to additional testing. At this point, I would not change anything, though my sample size is just one and the smoke control may be affected by variables that I don?t understand yet.


Mist Nozzle
Amazon.com - 10/24 Mist Nozzles -

Nozzle Thread Adapter
Amazon.com - Nozzle Thread Adapter -

?? Compression to Nozzle Adapter
Parker A-Lok 4FSC2N-B Brass Compression Tube Fitting, Adapter, 1/4"Tube OD x 1/8" NPT Female: Amazon.com: Industrial & Scientific

Garden Hose Valve
Amazon.com: Mintcraft GB9111A3L Garden Hose Shut-Off Valve, Brass: Patio, Lawn & Garden

Hose to ?? Compression Adapter
LASCO 17-8381 3/4-Inch Female Garden Hose by 1/4-Inch Compression Brass Adapter - Pipe Fittings - Amazon.com

Length of ?? copper refrigeration tubing (as needed)

Some pictures here:
WFO Smoke Suppression - Imgur

I'll provide updates as my sample size increases.

[david s]

Re: Smoke Abatement Solution

That's terrific. When ovens are new, or wet they smoke more. Also if you use the top down method of fire lighting you can have a pretty much smoke free firing provided your oven and wood are dry.

[Greenman]

Re: Smoke Abatement Solution

That is an excellent result. It may be able to help others with smoke problems as well.

The answer really is very dry wood and kindling and you will get very little smoke if you fire it up right. I don't have to worry about neighbours since they are well removed but even if I just build the usual pile with small dry stuff on the bottom grading up to larger material I only get a moderate amount of smoke for about a minute. It quickly settles down to emitting nothing more than a heat shimmer.

I guess some of us are lucky with plentiful good wood and have the luxury of having it under cover for an extended time even after it is what is considered to be dry.

[stonecutter]

Re: Smoke Abatement Solution

That's a creative solution, but - Any water going down a flue, no matter how much, is going to have a negative effect on your chimney liner and cause damage in a relatively short time....water needs to stay out of masonry structures, not introduced into them...even if you have a SS flue, more so if you have a clay liner.

I would rethink this if I was you. Have you tried charcoal briquettes or wood charcoal..something that smokes less than even dry wood at start up? What about a propane weed torch....they are cheap and you can preheat that way with no smoke at all.

Edit: just saw that you have a ss flue.

[Tscarborough]

Re: Smoke Abatement Solution

Page 153 Section 16 of the Residential Masonry and Chimney Handbook:

"During combustion, sulfur in the fuel will be converted to sulfur dioxide or sulfur trioxide, and hydrogen in the fuel will form water vapor. These gases will condense on cold walls of the chimney flue and react to form acids."

So adding water will make the problem worse. The solution is to keep the flue hot enough to eliminate condensation. In a house chimney this is hard to do, in an oven not so much of a problem. I would just recommend getting the flue up to temp with charcoal or a propane burner before firing the oven and injecting water.

[V-wiz]

Re: Smoke Abatement Solution

If you have problems with smoke and starting up the fire get yourself a weed burner like it was mentioned and make a draft door, the draft door will quickly start up the fire and keep it there.

[boerwarrior]

Re: Smoke Abatement Solution

Last year we had a party with a bunch of people standing around near the pizza oven, and I wanted to get it fired up without 'smoking everybody out.'

What I did: I started a wood fire in my Weber barbecue far away from the pizza oven and waited until I had a big bunch of embers, which I then transferred to the oven using a metal shovel. I left the embers in the oven for a while so that both the oven and chimney were able to warm up. Only then did I add more wood to the oven. The wood instantly caught alight and the smoke was quickly exhausted up the hot chimney.

Definitely not smoke-free, but resulted in a lot less smoke than starting a cold fire directly in the oven.

[jeeppiper]

Re: Smoke Abatement Solution

I can vouch for the weed-torch. Smoke is a result of insufficient combustion. Having that propane torch running during startup ensures that the wood is completely combusted until such time that the fire is hot enough to take over.

It is so easy to start too. I stack my wood in the entranceway, slide the stack into the center of the oven, light my weed-dragon and lay it on the oven floor and walk away. Come back in 5 min or so to smokeless blaze that can sustain itself.

Note: I store my week-dragon attached to a 20 gal propane tank under my oven. Extreme care should be taken to ensure that the tank is turned off at the source (not at the torch). The last thing you want is a slow leak in the closed area underneath your oven.....ka-boom!!!!

[V-wiz]

Re: Smoke Abatement Solution

FYI here is the draft door i built. Its very easy, and comes in use every time i fire the oven, whether its at the first start up or after the flames have settled down.

[deejayoh]

Re: Smoke Abatement Solution

FYI here is the draft door i built. Its very easy, and comes in use every time i fire the oven, whether its at the first start up or after the flames have settled down.

I think this is going to be on my summer chores list.

[MrGJH]

Re: Smoke Abatement Solution

Really interesting solution. I think you are onto something with this and the issues raised about water residue can be managed if the chimney is one with a right angle at the top. Mist is not going to run down the chimney and any runoff is right at the end and can be quarantined easily. Lots of options.

Really interested whether you did any more tests with this? Your estimate of less than 10% of the smoke sounds very promising. Smoke is a real problem in residential areas and this solution is very cheap to implement. I have been considering afterburners/catalytic converters, but this solution is not going to require any additional fuel or replacement parts.

Thanks for posting, interested in your subsequent results.

[v12spirit]

Re: Smoke Abatement Solution

FYI here is the draft door i built. Its very easy, and comes in use every time i fire the oven, whether its at the first start up or after the flames have settled down.

I was planning to consider something similar to your draft door for my indoor oven that I like to call: "smoke sentinel", it comes with a bigger air gap underneath. The major difference from your idea is that I see placing it before the vent (looking inward) will allow the oven to breath from the bottom of the door and the exhaust smoke will be channeled by the upper part of the door and forced to be driven inside the chimney.

[v12spirit]

Re: Smoke Abatement Solution

My neighbor complained about the smoke from my WFO. I probably would have done the same in his shoes.

that's an interesting idea. Never thought of that effect a nozzle can do! Interested to know the mechanics of nozzle effect on depressing smoke.

[knormie]

Re: Smoke Abatement Solution

An update:
After many firings, this solution is still working. The only thing I have to add is that the mister has such a fine hole that can be clogged and prevent the spray from atomizing. You can install an inline filter if you like or just unscrew the mister and blast it with a water-pik like I did. My neighbor has not complained since and my oven days are now stress free. Best of luck to you all.

[david s]

Re: Smoke Abatement Solution

Hi knormie,
I really like your idea and would also like to make one of these.
A couple of questions
1. What size diam flue do you have?
2. Where is the nozzle fitted to the flue pipe?
3. Is the nozzle angled down or aimed horizontally?
4. Does it run on mains water pressure or do you turn this down?
5. How much mess is collected at the bottom of the flue, assuming the smoke particles have to end up somewhere?