DIY temporary filter ideas


#1

Hi all, I ordered a Pro in December 2015. I will choose to get it without the filter when I get the “email”!
But the only place I can put it is not near a window so I am looking into making a cheep temporary filter to use until the real one arrives. I found one that looks like I could make but I don’t know if it will do the job. Does anyone have a better plan. Here is the link:
https://www.420magazine.com/forums/do-it-yourself/115176-diy-high-flow-carbon-filter.html

It looks like it will work but as you can see it is not being used for a laser cuter.


#2

I know nothing about the mechanics of air flow and particulates but I do have experience in these matters with a Glowforge. The exhaust consists of volatiles that you don’t want hanging around in your house and particulates that are significant and clog up the screen at the opening of my exhaust hose going out the window. So any filter will need to address both these parts of the exhaust air.

Also, all the discussion around air flow and filters in relation to the Glowforge’s ability to push air out the exhaust port seems to indicate that attention needs to be given to not have backflow into the laser and its internal exhaust setup. The filters that we used at Bay Area Maker Faire had active airflow fans in them. It wasn’t just a passive filter through which the Glowforge was connected.

Discussions of filters and exhaust setups can get into safety concerns and I would be hesitant to recommend any home made setup at this time publicly on the forum.

Here is a link to a topic that explores some of the issues with exhaust and venting.

Here’s a link to another discussion on a DIY filter:

And another one with some sustained discussion:


#3

A more viable idea might be to just get a cart with wheels that you can use temporarily for the Glowforge so that it can be rolled near enough to a window to use it with a vent. :relaxed:


#4

one thing to consider: a filter constructed to hide a grow room has a single issue to take care of, which is smells or odors. filters for laser cutters need to remove odors, VOCs, toxic fumes, pm, pm2.5, etc. it has more serious consequences for failure that you may not notice for a while. venting is the best solution, but you might also see if you can rent a filter from one of the bigger companies. lasers are rented so the filters may be, too.


#5

I also agree that if you’ve never built a filter before and haven’t read at least a few hours of articles from professionals to get acquainted with background research – don’t trust your health and safety to someone else. Caveat emptor: I’m a pretty tech-savvy dude with OCD tendencies to dig into details, but I’m not a professional HVAC engineer.

Edit: Also, in that linked post to mine… what I realize months later that’s not explained is that the top-half of it will be packed with a LOT of activated charcoal.


#6

I was briefly a professional hvac engineer. I wouldn’t build my own filter. You can get a good hepa filter for the particles and carbon for the smell and then you don’t seal it quite right and you’ll end up spewing that crap right into your enclosed space and as it’s been said the fumes and laser by products are not something you want to be sucking in. Professional filters have to go through so much testing and certification to prove they’re not going to kill you… just my thoughts on the matter


#7

Another vote for nuh-uh. There are air filters for woodworking that could probably (!) handle the particulates, but you’d still need the carbon side, and that kind of airflow is just darn loud.


#8

See? There you go. :grin:

I will point out that my design fits my needs, in that I’m not going to lase anything toxic to start with. If I would be putting it in a place, like a school, with other lives or there was more of a chance someone would put a material not properly researched in for burning… there’s no way I’d do it.

If I get a bit of smoke from wood, paper, maybe only leather in my condo… I wouldn’t be upset. Chlorine gas, however… no. Hells to the bells no.


#9

There is absolutely no way that I would trust a 5-gallon bucket of charcoal and some plastic aquarium filter material to deal with the smoke, fumes, gas, and particulate that laser cutting will produce. That might just_barely_ work to filter the smell from a few plants… and not for very long.


#10

I disagree. Those types of filters are common in the agriculture business. I’m not a grow-op custodian, but it’s just a DIY plastic bucket version of this commercial version. But “how long” it lasts is academic… filters need regular replacement depending on workload.


#11

I was a -legal- grow-op custodian/compliance officer for a few years. We used the 4’-tall ones with a 10"duct opening. They were heavy, expensive to buy, expensive to fill, and didn’t work that great.
I wouldn’t trust it for a laser. YVMV.


#12

I don’t doubt your experience, and that’s cool and all, but it’s also two different industries. Filtering for plant odor/pollen versus smoke particles would produce different results because the micronic size of what is being filtered. Plant smell should be easier to filter out, I admit… but the filter design also typically depends on at least charcoal AND a fabric filter. The fabric could have been lackluster.

Helpful chart: https://www.coloradoci.com/bin-pdf/5270/ParticleSize.pdf

Would I risk lives on an agro filter for lasering either? No. But in the basic principle of operation, using charcoal + HEPA is the generally accepted practice for filtration.


#13

Yeah, I agree. The chat you posted shows that plant smell requires 0.1 micron filtration, and coal/tobacco smoke (maybe closer to what we would produce with the GF) requires 0.01 micron filtration.

The tighter the filtration level, the harder it is to push air through. So you need more CFM. Which puts more pressure on all your ducting, increasing the potential of a failure.

I don’t think the blue aquarium filter media that was used in the DIY article above would rate as a HEPA filter. I could be wrong. It being in a home depot bucket isn’t the bad part per se, just limits the amount of activated charcoal that you could load.

Meh. not really. That industry is in a constant state of worrisome flux. By the time I got myself out of it, I was owed $20,000 in backpay (uncollectable), and had to cut relations with a lot of people who got greedy and turned into total scumbags. Best part was doing compliance walkthroughs with the chief of police and the fire captain.


#14

Well I am very glad to have this forum! Thanks to all for all the helpful information.
I think the advise I will take at this point is to put wheels on the table and roll it to a window.


#15

Thank you Jules, looks like that is my best bet. I hope the filters come soon!


#16

Not really. You need more pressure to maintain the same CFM.


#17

A few folks have supplemented or replaced the 8 foot length of the supplied exhaust hose with an extended exhaust setup that has appropriately powered and ducted assistance to go longer distances. No in line filters, just longer duct work to get the exhaust of the room and outside. I think the booster fan idea has some merit for some folks and then obviates the need for a cart.


#18

It’s been argued that you don’t want denser filtration for particles which would limit airflow to capture small diameter particles, you want to increase the amount of filtration material in general to be more effective.

http://www.tandfonline.com/doi/pdf/10.1080/027868290503109

To pick apart the posted filter, the blue aquarium filter media (likely a polyester) alone isn’t good enough. It causes the incoming particles to slow down their kinetic energy by presenting a “random path” before striking the charcoal. Those slowed particles would have more chance to be absorbed by the charcoal. Adding a pleated HEPA filter would capture any smaller (or stray) particles that makes it through the gauntlet of coal, but the filters dramatically reduce airflow.

Really, if maintaining airflow is a high concern, it’s better to recirculate the filtered air a second or third time rather than trying to filter everything in one single pass.


#19

Maybe we’re looking at this all wrong.

Maybe conditioning the exhaust to accommodate human needs isn’t the way to go.

Maybe humans need to adjust in order to meet the requirements of the exhaust environment, in which case this has a very easy solution:

Have everyone in the house just wear Personal Protection Equipment, ie: respirators or fresh air supply hood systems like those used by automotive refinishers.

:stuck_out_tongue_winking_eye: Of course I am just being felicitous. :smiley:


#20

Filtration by diffusion into the filter rather than deposition onto the filter… you are right. That had slipped my mind.

My takeaway from that article is that industrial HEPA filters create more pressure drop than standalone residential air-cleaners, and that residential air-cleaners could be improved by being less like HEPA filters.
The comparison is a little weird though, since when I think of industrial HEPA filters, I think of something connected inline with ducting, while when I think of room air-cleaners, I think of a standalone device of some kind.
The pressure drop in a stand-alone device results in increased power draw for the fan (?) minimizing efficiency, while the pressure drop created by an in-line filter not only affects the efficiency of the fan, but also the pressure in the ducting; the results of this would depend on the length and type of ducting, and the location of the fan in relation to the filter and the ducting run. Might vacuum-crush flexible ducting if you have created negative pressure in your run, or blow out taped seams in you have created positive pressure.

Eh, whatever, looks like @nancielaing is going with the much easier and safer solution of rolling the GF to a window and venting outside.