Homemade Filter

OK, don’t blame me, Dan suggested it in the latest post XD

I wish I had the money to pay for the air filter add-on but even if I did I think the additional wait might put me off. Also, I live in the UK so that’s more import duty and VAT when buying new filters. So with all those excuses in my corner…

I was thinking of using a cooker hood extractor fan to pull the exhaust through a HEPA filter and then drive it through a charcoal filter to scrub the majority of the nasties. But that would still require a modicum of ingenuity. Then I saw this!:

I figure this will draw the exhaust and filter the particulate. I can then just use the blower function to particulate-free exhaust through a charcoal filter. And, it’s just over the same price I can find a good quality 4" inline extractor.

I hasten to add that the exhaust will still be being pumped from my :glowforge: through the partition wall in the middle of my garage, scrubbed and then left to make its way out under the garage door. There’s a PVC door between the section I’ll be working in and the section where the output ends up. Anyone else planning anything similar?

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No. Just… No.

a) A kitchen cooker filter will provide next to no filtration whatsoever
b) £162 for a mini shopvac to use as an inline fan is insanely expensive
c) Lots of other people have discussed this. https://community.glowforge.com/search?q=DIY%20filter


Ouch… thanks for that.

I wasn’t considering using the cooker hood to filter anything. If you’d actually read my post, I was thinking of using the fan from a cooker hood to pull the exhaust through a HEPA and then drive it through an activated carbon filter. Which would provide plenty of filtration.

A £162 mini shop vac might be expensive if the ONLY thing I was going to use it for was an extractor for the GF. But, it also has the small added advantage of being detachable from the exhaust line so I could use it as, um I dunno… a mini shop vac? In which case, It’s not that bad, and cheaper than the GF filter


Sorry, you’re right, I did misread parts of your post as I only glanced over it.

The cooker fan to do the first stage of exhaust pulling – the fan would be very weak. It’s designed for virtually no air resistance, because the filters themselves offer next to no air resistance. The layers of HEPA and charcoal needed to do proper filtration creates a significant back-pressure that the cooker fan would be horrible at dealing with.

Also, buried somewhere in previous threads where this has been discussed, the Glowforge has a pressure gauge that will shut down the Glowforge if you have too much backpressure.

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I’m thinking about building a similar filter, but I’ll probably gang up 4 or 5 120mm fans that I have lying around to use a larger surface area. I’ll probably go with a cheap filter for most particulates, then a MERV 13 filter for smoke, place the fans next, then a charcoal stage, then another cheap filter to catch the charcoal dust.

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Confirmed. The louvers on my PRU exhaust setup stuck once. The Glowforge spun the fan up to max for a moment, detected the back-pressure, and promptly shut down.


Although I don’t think I’ve seen any confirmation about the Glowforge being affected by too much positive pressure, like feeding it into 500-600 cfm suction. Not that I’d do that much, but there has been concern of having so much positive pressure that you effectively turn the Glowforge’s fans into generators by overdriving them, possibly burning the electronics out.


OK, to clarify, I WAS thinking of using the cooker fan unit but I decided that the mini shop vac would be a better alternative since it’s designed to filter particulate.

But I’m convinced that a cooker hood fan (which is designed to pull a large volume of air through a thin wall filter and then a carbon filter) would be adequate. I’m not sure if you think I’m talking about a little bathroom extractor fan (I’m not). This is the kind of thing I was thinking about (144 CFM):

With that said I see mention in old topics that GF requires 200 CFM… :astonished: so if that’s the case, the shop vac really wouldn’t do it (33 CFM).

I’ve just checked the history of the topic though - sorry I should have done that, my mistake! - and your first design proposes to use two 20 cm fans to pull it through both the HEPA / car filter and then the carbon. I’m less convinced in the ability of those fans to cope than the cooker hood extractor fan to be honest. I definitely think it’d be best to pull air through the filter material and then push it through the charcoal. In my experience systems like this are more capable of driving than pulling. But… that’s just my experience.

I’m in Canada, you’re in the EU. There’s probably different construction practices to keep in mind. My idea of a cooker fan is a simple 4" fan in a hood assembly. What you pasted isn’t anything I’ve seen in a hood fan assembly here.

I don’t even think my design is the best. I might build it to see if I was right in some of the details, but I’ve heard enough compelling arguments about other designs that I’ll be redoing it again depending on what my results are.

some of these filter solutions discussed in the thread are useful for one thing only: pre-filtering exhaust before directly venting it outdoors. none of these are safe to vent inside a room you’re also breathing in.

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Yeh fair point - all the ones I’ve ever had on cookers have made a hell of a racket and are designed to pull 100+ CFM through two filters over 12x12" so they’re pretty serious business.

After reading down that previous post a bit I see you’re relying on the :glowforge: to drive the air towards the filter and then relying on the pull from the two fans on the other side to encourage it. That makes more sense. I’d be a little worried about leaks dissipating some of that pressure but otherwise I’m just surprised by the CFM they’re producing!

I’d be interested in how well it works. Do you know anyone who works for a gas / oil refinery lol - odd question but you could bag the exhaust from your home mad filter and have them run it on a Gas Chromatograph for a rough estimation of how clean it is - and maybe even what’s in it if they have anything that sophisticated.

Yeh roger that - as I said mines going to be dragged through a sealed partition wall and vented into a small room I’m not using. That small room has a garage door with the normal slit at the bottom open to the street. It’ll be isolated from the workshop and I’ll just open the main garage door to vent that room at the end of a run. I could also add a small extractor fan to recycle the air in that little room but either way I WON’T be in it. I’m mainly worried about smelly fumes escaping under the garage door and annoying the neighbours.

i mean, i think it’s still a terrible idea to vent it in your own structure, at all. but regardless it needs to be said every time these threads pop up in case someone builds a terrible diy filter and vents it back under their desk.


Hmm, sadly I’m short on options that way :frowning:

I can’t drill holes in the front of the house and place an exhaust vent in it 'cos… restrictive covenants. I can’t take it out the back of the garage without going through the hallway, the kitchen and of course, my wife’s dead body first :laughing:

So, pre-filtered, pre-scrubbed, vented into the unused part of the garage it is. I might find a way of slipping a thin wide exhaust port wedged under the garage door but we’ll see.

I was also wondering if anyone had thought about carbonisation / heat treatment. If most of the nasties are VOC’s then they’re all combustible. I was wondering if some kind of heated mesh might burn them off but can;t find anything on the web about that approach. Finally, water treatment? Can you not bubble smoke through water to catch the particulate at least?

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Exactly this.

I expect I’ll have very modest toxic smells, mostly wood products. Maybe (MAYBE!) some very small quick cuts of acrylic. I’ve got table space reserved sitting beside a patio window which I intend to fit a few 6" planks and make a 4" venting hole for the winter. That’s my preferred solution.

you’ll get some filtration but nothing a decent filter isn’t going to catch, and water otherwise doesn’t work that well or a bong wouldn’t be so functional.

more interesting would be whether it could function to catch water soluble vapors as part of a ridiculous multistage trap that probably still isn’t worth diying but would be hilarious.

[quote=“jrnelson, post:16, topic:9397”]
well or a bong wouldn’t be so functional.
[/quote] Lol I wasn’t even going there.

See, what gives me hope is that Glowforge are clearly doing this. On a fairly small footprint and with a fairly low cost. So it’s possible. It just has to be well made and then well maintained. I’m very curious as to how Dan and co and planning on guaranteeing it’ll keep you safe without either testing the output or knowing exactly what you’ve cut and for how long. That seems impossible to me.

sure, and you could build your own filter now if you tracked down the filters they use in industrial laser filters, built a box around them, added booster fans, etc. where i think too many take a misstep is by hacking together things out of furnace filters to filter laser exhaust (vs a cheap box fan general room filter).

by all accounts the filter isn’t so revolutionary apart from fitting together in the same footprint, affordable, etc. they’re obviously getting quality filters but i don’t think the filters themselves are likely to be particularly magical - because if they were they’d stand to make more in that market than they ever would selling lasers. you might be able to buy their replacement filters at some point and try putting something together. but even then you’re looking at buying $200 filters, which is a far cry from most diy filter goals.

Guarantee? Uhhhhh… that’s hopeful of you. :slight_smile:
All they can do is make recommended filter replacement schedules and hope that you’ll follow it. If you fail to, guarantees go out the window.

This is quickly becoming a safety-issue related topic that I’m going to defer to Glowforge lawyers about.

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Lol OK, maybe not guarantee but I’m interested in how GF will handle this since the lawyers seem to be on pins about liability.