I don’t understand…seems to always be 2 steps forward 1 step back with ventilation for me! After having got to the point after many attempts where I was able to roast with almost no backdraft and no air quality spike it’s now just suddenly returned to the extent I need both doors open to avoid massive smoke build up in the roastery.
The only thing I’ve done is clean the roaster and the Airwave. All the positioning and everything else is the same, and I can’t understand what I could have done during the cleaning process to have changed the setup! I cleaned the chaff filter baskets, the chaff collector box on the bullet, brushed inside the exhaust track and ran the self-clean cycle on the Airwave. I removed the face plate like normal and cleaned the IBTS sensor and vacuumed around the drum.
Any creative thoughts about what might have caused this would be appreciated as I’m totally stumped!
After I read your other post and this one, my initial reaction was, ‘are you creating a vacuum in your roastery, what type of clean air do you have coming into the space?’
I’m no expert on this, and I’m still trying to fine tune my roastery and getting as much smoke out as possible myself; but I printed off the 3D parts that attach to the cooling basket as well as the top exhaust fan. Those pieces meld nicely into my ductwork. Around 3 feet from the exhaust fan, I run an inline exhaust fan which pulls around 400 CFM’s. Even with this setup, I still get smoke lingering around where my own air purifiers show a dreaded red light, aka - air is bad. My roastery is in my detached workshop on the second floor and it doesn’t have any windows/vents up there outside of the 6 inch exhaust vent I have connected to my inline fan. A friend of mine who is in HVAC shared I’m essentially creating a massive vacuum in my roastery. The problem I have is I am evacuating bad air, but I’m not replacing it b/c this room has no windows or vents bringing in equal or greater than 400 CFM of fresh air. As a test case, I bought a cheap VEVOR Portable Ventilator with 30 foot hose, which can pull 2,000 CFM into my room. I figured the fan would bring in fresh air from the downstairs open window and pump fresh air which would break the vacuum and allow the bad stuff to get pumped out quickly. I’ve roasted 4x and I see no noticeable difference except it being loud from the fans. I was going to open up my roof to install windows or a mechanical eave, but if this test didn’t work then I’m at a loss myself.
I’m just as lost as you are 
Old home roaster, new Bullet user. “Old” means I have had a variety of solutions to ventilation over time. The range includes roasting outdoors in a non-windy location, roasting next to an open garage door, roasting on an elevated stand below a small commercial hood, and this, which works best of all:
I’m still in the garage, this time with a cheesy $20 box fan in the window, set to its lowest speed. The 6” to 3” adapter works great for the drum ventilation, the decrepit looking 3” pipe is direct connected to the bean cooling tray with the rest of a 1m piece of 75mm heater flex duct.
The fan keeps all but light whiffs of roast smell away, the ducts are very effective at evacuating virtually all the typical smoke, including the heaviest parts of the roast.
I think my problem this time may actually be excess smoke being produced by the roaster itself…I noticed smoke still coming out of the exhaust tube even when the roaster was empty and the chaff box was off. I’m now trying to investigate whether there is some smouldering which has resulted in an increase in the smoke. Still struggling with exactly where to start though…
are you getting chaff buildup surrounding the drum? sometimes chaff builds up and then it just burns to a char.
usually more often with naturals. i used to blow air through the rear vent to expel the excess chaff after a roasting session, but currently in need of a new one, since the old one was too powerful.
Prior to moving upstairs to a dedicated space, my setup was identical to this and the CFM’s the box fan was able to move was exceptionally better.
After each roast, I use a vacuum to clear the drum/exhaust tube/ and if it’s a ultra chaffy bean I pull off the chaff locater and clear that as well. I suppose it’s possible there is some oil build up somewhere that is causing the smoke. Is the duct work getting hot by chance? I replace my ductwork once every few months b/c of oil copious amounts of buildup in there. Thus, I use disposable flex tubing instead of rigid ducting.
ah, sorry, @md19600.IwXw i was replying to @adam.cTfR
i can’t really say for sure about your situation. but because there is no seal between the main drum and the insulation fiber, you have to be careful if you blow air into the main drum. tech support said it was fine, but now having taken it apart myself and seeing it, i think they may have misunderstood my question at the time.
but more directly back to smoke and airflow, i did notice smoke coming from the tryer and that prompeted me to remove the drum and look inside, and it is important to vaccum or softly blow out the chaff surrounding the drum. with washed coffees, this isn’t usually as much of a problem, but i recently started roasting naturals more frequently and so this was my first experience with chaff build up outside the drum causing airflow and smoke issues. because smoke was comingnout the tryer at F3. which had never been an issue before. but yeah. i skimped on it a couple sessions and so important part of maintaining. as it can also lead to ventilatikn issues if the smoke isn’t fully exiting at the rear impeller.
note: this is note an issue with the machine, but more so a brief maintenance oversight on my part.
as for backdraft in general, airpressure in the room in important. i recent roasted in a room with only one window, and i used that window for the airflow exhaust, but it created a vacuum of sorts, and did not ventilate efficiently. the Aillio bullet, as many home machines seem to be, as closed system. whereas a roasting machine is acutally integreted with the airflow normally. it would be interesting to see Aillio develop an airflow solution that integrates with their app and settings, but for now it is easy enough to just make sure there is sufficient airflow in the room.
How often do you change your flex (in terms of KG roasted?). I have a small amount of flex going into my airwave and I’m wondering whether I’ve not changed it in too long and it’s causing static build up / resistance.
So I just discovered this this morning. I didn’t remove the drum but I tipped up the roaster with the faceplate off and a giant pile of ash just came out onto my workbench. I thought that vacuuming around the drum every few roasts would be enough to keep it clean but evidently I hadn’t appreciated this build up!
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I think there’s an extent which I might be coming a bit too obsessed with the real time metrics. In production health and safety terms, my spike is still within acceptable limits and I am able to get it cleared and the levels back down even on a smoky natural within 30 seconds to a minute or so. It’s difficult to know when being conscious of it and seeking to constantly improves goes too far and I feel like I could be at that stage and I’m never going to fully eliminate a PM spike when I drop 1kg of relatively dark roasted smoky natural…
@adam.cTfR
sometimes that obsession makes one a better roaster.
yeah, there may never be a truly healthy way to roast. but as long as it is minimal and only coffee fumes, it has to be better than typical smoke. right? or at least if your room is not a vacuum. i felt it a bit unpleasant the couple times i roasted in small rooms or rooms with little airflow to conpensate the exhaust flow
I change it whenever the inside tubing resembles brown fur, like I’m petting my shorthair lab 
