I installed a range hood in my garage for my HotTop and it wolrked well enough with the standard grease trap filters but it canāt keep up with the Bullet.
I have ordered some Merv 8 furnace filters from Amazon that will cover the Grease filters and am planning on holding them in place with some angle aluminum and some Brush seal weather stripping so that I can just slide the furnace filters in and out as needed.
if your range hood is made of steel or magnetic stainless steel, you might be able to creatively use some magnets on the filter to hold them in place when you are roasting coffee and then remove them when you are not roasting coffee and want your kitchen to look normal.
I posted some photos of the range hood getting clogged without extra filtering in the āCombination venting and cooling setupā thread.
The new filters will arrive on Tuesday. Iāll take some photos and post them here.
I use an air filter on my exhaust to catch some of the particles before it hits the S4. Havenāt looked at the S4 since I installed it and itās working fine. I roasted s lot more than 5KG.
FWIW, I cut a new piece of filter every 8-10 roasts as it gets clogged.
Hereās a post where I shared the filter : Feedback on New Ventilation Set Up - #9 by lgd
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Mine keeps up well enough since itās rated at 900 CFM.
I was thinking the similar, to get a pleated furnace filter or a sheet of the similar type of filter as the one in the cooling tray and āhangā it off the baffles using wires or paper clips 
Unfortunately my vent hood is not magnetic stainless steel.
And actually post pictures I took scissors and cut off the cardboard X to improve airflow. I do find I have to turn the fan up about halfway to get good smoke extraction. The filters definitely impede the airflow but if it keeps the fan motor clean itās ok.
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Here are a couple of photos of the pleated air filter that I was able to install on my Range hood in the garage. I was able to slide a couple of magnets under the cardboard. (I pulled them part way out for the photo)
The discoloration on the filter was from one roast: 450g, 410 drop, 2.49 minutes after start of first crack. I could not detect any impedance of the air flow. There is a lot of surface area.
Some of my other hacks are visible in the second photo:
Stirrer
Clip on bean deflector
Extended door handle and magnetic catch to hold the door open.
Blue tooth microphone so I can hear the beans cracking.
Red paint line painted on the funnel and the bullet to verify alignment when charging beans.
Letters on the buttons painted red.
Half of the handle of the tryer painted blue, so the orientation of the tryer is obvious.
The Bullet is mounted on a lazy Susan so that I can rotate the bullet to easily access the chaff collector for cleaning.
It is still a work in progress. I currently have a mocked up cardboard shroud and need to add a dedicated receptacle for the power so the wiring is cleaner.
It never endsā¦
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Yeah, Iāve been thinking a lot about this filter issue lately.
I did my second three indoor roasts under my vent hood last weekend. I had a sheet of 3M āhammock filterā that I cut a piece out of. The hood vent suction is good enough that I just place it, and the suction will keep it in place. The Bullet exhaust was just below this, and the vent hood seems to catch all the smoke just fine.
I did 450g x 3 to about a City+ level, and you could see the brown oil stain on the filter, and even on the vent hood filter/baffle afterwards. It makes me a little nervous that this will eventually gum up the hoodās fan motor over the long term.
Iāve ordered some of the 3D printed 4" al tubing adapters for exhaust and cooler fans on Etsy. I think Iām going to rig up a portable flexible vent to go out my kitchen window. Itāll be cheaper to sacrifice my cheap 4" inline fan (which I will try to protect with those 3M filters) than potentially have to repair my vent hood fan down the road.
That looks interesting to use for my purpose to try out - Iām going to see if I can get some from either Lowes or Home Depot tomorrow. I too have sometimes noticed brown stains on my baffle filter but not every time I roast, interestingly enough esp since I roast to just second crack.
If you donāt mind, who on Etsy did you go with to 3D print the exhaust and cooler fan adapters? I definitely can use the cooler fan adapter. Thanks in advance.
My kitchen range hood (which I use for food, not bullet) takes these metal+charcoal filters. Wont catch on fire, and maybe better at dealing with oils than a paper filter?
The pleated filter that I chose is rated for MERV 8. Amazon has higher rated MERV filters in the same size.
I wasnāt aware of the MERV rating system.
From the epa.gov website:
What is a MERV rating?
Minimum Efficiency Reporting Values, or MERVs, report a filterās ability to capture larger particles between 0.3 and 10 microns (Āµm).
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This value is helpful in comparing the performance of different filters
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The rating is derived from a test method developed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE).
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The higher the MERV rating the better the filter is at trapping specific types of particles.
| MERV Rating | Average Particle Size Efficiency in Microns |
|---|---|
| 1-4 | 3.0 - 10.0 less than 20% |
| 6 | 3.0 - 10.0 49.9% |
| 8 | 3.0 - 10.0 84.9% |
| 10 | 1.0 - 3.0 50% - 64.9%, 3.0 - 10.0 85% or greater |
| 12 | 1.0 - 3.0 80% - 89.9%, 3.0 - 10.0 90% or greater |
| 14 | 0.3 - 1.0 75% - 84%, 1.0 - 3.0 90% or greater |
| 16 | 0.3 - 1.0 75% or greater |
HEPA is a type of pleated mechanical air filter. It is an acronym for āhigh efficiency particulate air [filter]ā (as officially defined by the U.S. Dept. of Energy). This type of air filter can theoretically remove at least 99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (Āµm). The diameter specification of 0.3 microns responds to the worst case; the most penetrating particle size (MPPS). Particles that are larger or smaller are trapped with even higher efficiency. Using the worst case particle size results in the worst case efficiency rating (i.e. 99.97% or better for all particle sizes).
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I bought them both from this guy. Just received them in the mail today. Havenāt installed either yet, but looks to be a good solution:
I had some quotes locally, and, for a single piece, were higher than both the pieces together, shipped to Canada from this seller. The exhaust adapter is a little tight on some semi-rigid aluminum duct, but Iāll pick up a flexible one, and it should work just fine.
I didnāt notice brown staining on the hood vent filters on my first three roasts, but those were pretty light, just to city.
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Thank you! I just looked at his listingā¦ heās Bullet owner too, he says 
Iām looking for the cooling tray adapter and he has it too. Awesome!
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Hi Bill what is the blue tooth microphone you have there.
from Amazon:
With it, I can easily hear first crack. Second crack, not so much. (But I have hearing loss and seldom venture into the second crack)
I also use a piece of 1/2 ID by 3/4 OD silicone tubing to adapt to the trier hole.
I had to taper the end of the tube with an exacto knife.
It has recharable batteries via USB
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Thanks, Bill. I think Iāll give that a try especially for the softer beans, I have some Brazil that I have never been able to hear first crack just go on temp and smell.
Iāve found this thread very helpful for setting up my exhaust solution. Hereās my V1 and V2 setups. The V1 was using the 3D printed exhaust adapter, but I found that more smoke was escaping than Iād like, so I went to a hood type setup. That one is better, but a little smoke still escapes if I go to a fan speed of F4 or greater.
I do have a bit of 3M hammock filter in the line to catch dust and oil before it hits the fan, which does restrict the airflow a bit. I will probably try some of that pre-filter material some have been using, and maybe that would restrict the flow a little less. The real solution is probably to move to a more powerful 6" fan (my 4" fan is 150 cfm and not quite as powerful as an S4, which I do also own, but am using for something else). But Iām going to try and make this work with what Iāve got. Worse comes to worse, Iāll remove the filter completely, and just clean the fan more often.
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Pretty impressive. What about using your range hood there at low speed to pick up stray smoke?
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Thanksāyep, I am doing that, but, I kind of just want the other system to do it allāno reason especially, other than I want to solve the problem. Also, I find 1C kind of hard to hear on the Bullet, so the less fans I have running, the better. But, for now, the hood fan runs to pick up that stray smoke.