Exhaust hood options


Hi everyone! I guess we all have received the email from Aillio about recommended exhaust configurations for the Bullet. Until now I have simply placed the roaster below the stove exhaust hood, but I am considering getting a dedicated/more effective solution.

What do you recommend? I am looking after models available in the EU. But feel free to share your setups, even if it only serve me as inspiration.

Thanks in advance for your help.



I was glad to see some vent guidance from Aillio. We have seen damage to bullets from bad venting. The main issue is people connecting some tubing to the back and directing it outside- especially over distances more than a meter or two. What happens is that as the coffee dries out in initial roast phase, all that moisture being lost is retained in the vent tube and drips back down into the machine when roasting is finished. Or it might be condensation from outside. We see all these signs of moisture in the chaff collector, rear fan and back plate.
So whatever design in needs an air gap. I think just roasting under a stovetop type hood is ideal. Or some other way of venting the area around the roaster without connecting to the machine itself. The other issue is connecting a powered fan via a tube to the roaster. If the air draw is too strong I think you are going to change the thermodynamics of your roasts! Sucking heat out, literally.
Anyway in the US we have a tons of vent fan options. Dryer duct aluminum tubing is not the best but
Cheap and easy to work with.
Just a few thoughts !


What email would that be? When did you receive it?


But why? Under a stove hood appears to be the safest method for the Bullet. Works well for me. It lets the Bullet control it’s own venting pressure as opposed to hooking up to a tube that might cause too much back pressure or pull the exhaust out too fast, affecting the roast. Unless you are roasting so dark there is a lot of smoke to get rid of, I would stay with the stove exhaust.


You can sign up for Aillio’s email newsletters on the top of their homepage…


Thanks, unfortunately it doesn’t work here. Nothing happens when I click the button (even with adblockers disabled).


Try this link to get to the sign-up page for the Aillio n/l.

Or just go to the Aillio.com site and scroll down to the bottom of the home page to find the same link.



Still testing this setup but seems to work just fine. Cloudline S4 (200cfm on high). Roasted day before yesterday and zero smoke/steam bypassed the funnel.


I used the Cloudline S4 as well. Works fine, relatively quiet and uses minimal power at max speed. My makeshift “range hood” is an old 11" x 16" storage box with a 4" flange installed, dangled above the exhaust port as you have done. Mine is pretty ugly, but it gets it done. When my Bullet exhaust fan is at a high speed the Cloudline is hard pressed to keep up (I’m surprised how much air the Bullet is capable of moving!). The real bonus is the amount of brown oily residue clinging to the inside of the “hood”. Glad I’m not breathing that stuff!

Someone here used a large stainless mixing bowl for the collector… a really nice looking installation. However I could see myself missing yet another finger trying to cut the hole so I went the ugly route!



This is my solution for the smoke. After having contaminated a cheap bathroomvent, I bought a professional vent. They advised me to mount a filter chamber and that’s what I did. Don’t laugh about the strange S curve in my pipes. Had to rearrange them and didn’t want to drill a new hole. Hope this is not giving problems with condensing water.


Wow! That’s some studly looking plumbing! I understand completely about not cutting more holes in the house. :smile:

I prefer to roast outside, so I did the minimum for cold weather roasting-

Ugly, but it gets it done. These days the interior of the ‘hood’ is yellowish-brown. That would have been my lungs without this kluge.



Well, it’s not that bad at all ! The inline fan looks good. Perhaps you could install a simple filter. My former fan broke down because it was congested with coffee oil.


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My former fan broke down because it was congested with coffee oil.

Uh-oh… I thought you were concerned about chaff! Guess I’d better get something in front of the fan.



Here is my setup.
The exhaust divided, one for the roaster and the other to speed up the cooling process.


Nice solution.

There’s another issue with the cooling tray which your implementation addresses. Without something to grab the cooling tray exhaust, there’s a white residue which collects on the bottom of the Bullet. Dunno if that residue/smoke/dust (??) gets to the components but what you’re doing should keep that from happening. (I wonder if it might help keep the IBTS clean?!)



Curious about your set up and the guidance of keeping the exhaust less than 1-2 meters. I am designing a similar system where I’ll have the hood above the roaster connected to duct fan using about 2 feet of duct. I’ll then need additional duct from the fan to the exterior wall but this length is probably another 3 feet. What is the overall length of your exhaust solution? and do you know if the 1-2 meter (big range there) guidance is for the entire exhaust solution of just from the roaster to the fan?
Many thanks.


The Aillio limitation of 1-2 m was for an unpowered exhaust duct attached directly to the Bullet. Preferably that duct was to be straight (no elbows or bends). I have misgivings about a passive duct like this because of air drag in the duct as exhaust moves to the outside and because air pressure differences between the building interior and the exterior ambient pressure will directly affect air flow thru the Bullet. Make-up air for the room is critical for a passive system in order that the Bullet exhaust fan can operate unaffected. In addition, air movement outside the building can affect the passive flow rate. Now comes too much info…

An alternate is to add in-line, powered air movement with enough flow rate and connect that powered exhaust duct directly to the Bullet. In this case you run the risk of the external exhaust affecting the flow rate of cooling air thru the Bullet. Anything that alters the air pressure at the Bullet exhaust vs. the air pressure at the Bullet air inlet (lower rear of the Bullet) affects air flow thru the Bullet and consequentially alters the air flow for a specific F#. That essentially overrides the Bullet’s exhaust fan.

However, if you leave a gap between the Bullet exhaust and that powered ducting (the range hood you plan to use is a great example), the external system can sweep the air space without affecting air flow thru the Bullet because air pressure at the Bullet inlet is (probably) equal to air pressure near the Bullet outlet. Under these conditions the duct length can be whatever it takes to get to the outside to the extent the flow rate is high enough to move contaminants outside before they condense or attach to the inside of the ducting. @bertje1959 (above) suggests a filter to collect the contaminants which is a great idea.

Assuming you have a source of make-up air like an open window or door, a powered external exhaust system (range hood or a purpose-designed exhaust system) can keep the air fairly clean (it’s not perfect!) without affecting Bullet roasting profiles. Just keep in mind that after you shut off the roaster, oils inside the drum and the exhaust will evaporate and cling to everything in an enclosed space. That’s a vote for keeping the exhaust system running longer than just while you roast.

Also, an air-gap connection is the current recommendation from Aillio.



Here is my second evolution of an overly complicated exhaust. The inline fan is the Cloud S6 that so far I have only ran at half speed (there are 8 settings) and the cone has a filter material that seem so far to be doing an exultant job, no residue seems so far to get beyond the filter. There is a 6in gap between the end of the exhaust from the Aillio into the cone and the filter at the neck of the cone.