DIY air filtration unit for <$200

[Dan Hintz]

Thanks for the reply and your trying to help me with this. So you're saying that if I cut down on the bends in the ducting, that will increase the airflow. Are you then suggesting that with this increased airflow, the carbon will extract more fumes? I thought you said if air flow is too high, it can pass through the carbon layers too quickly. I don't have any issues with airflow, the smoke and fumes are being pulled from the laser just fine. It's the smoke and fumes not being removed from the air before it leaves the extractor that I'm having issues with.

As Greg said, if any smoke is making it past the HEPA, you don't have a HRPA (or a leak)... that said, if you have that level of smoke getting to the HEPA, it will be filled of particulate matter (and rendered useless) in a very short time. If you notice VOCs coming through, you have the option of making your carbon bed thicker or slowing down the airflow.

Also, if you don't sandwich the carbon between filters, you run the risk of levitating the carbon with high airflows, which will reduce cleaning efficiency. I chose to run the air downwards, letting gravity and the airflow work together to keep the carbon packed.

[David Somers]

Morning all,

Since this has been a long running thread I thought I might provide an update. I was checking on carbon prices recently as I ever so slowly prepare to buy a laser someday. I contacted sales at General Carbon, the source Dan Hintz originally mentioned. They said they no longer had the 3mm pellets in stock but felt the 4mm pellets would do just as well for this use. Part number C-40. $121 for 55b bag with about $53 SH from NJ to Seattle. (apparently too big for a forever stamp....sigh) They also said part number GC 4x8S at $90.75 for a 55 pound bag would perform equally in this case and was less expensive. Same S&H.

Also, not sure if this changes the pricing at all, but Dan had mentioned he bought his HEPA filter from Sears. All the Sears stores out here seem to be going out of business at the same time. Might be worth checking your local Sears store to see if you can get a filter at a better price if they are offering Going out of Business Sales. Prices for them overall seem to have gone down a modest amount since the thread started way back when.

Hope this helps someone! And thanks Dan for shepherding this multi year thread all this time!!

Dave

[Gary Hair]

Is all activated carbon alike? I found some that is marketed for fish tanks that is about 1/2 the prices elsewhere but it says it's for fish tanks.
Here is a link to the manufacturer:
http://www.acurel.com/index.php?opti...d=17&Itemid=75

[David Somers]

Gary,

The variance is in the size of the charcoal and the material it is made from. What gets used in fish tanks is often a finer material than what gets used for air filtration. the finer particles makes it harder to move a volume of air through it. The size of the particles in the stuff I mention above is 4mm cylindrical pellets. Stuff used in aquariums tends to be crushed into a much smaller grit.

Although it is not the case with the Charcoal I mentioned above, many air system charcoals have chemicals added to them to help remove certain types of gases as well, depending on the needs. In HI I used one that had specific additives to remove Sulphur Dioxide from the Volcano. I used to maintain a big salt water fish tank and noticed the big differences between what got used there versus what was used in air systems.

Don't know if that helps. Others here may be able to provide more in depth differences as well?

Dave

[Glen Monaghan]

My first attempt was with a batch of stuff reported to be made from coconut husks, pieces that were on the order of 0.5-0.75" cupped/curved shapes, and it was not particularly effective in a 4" thick layer. Probably just too coarse. Better than nothing but insufficient for use when cutting acrylic. I'm currently using GC4x8S, two 4" thick layers, which works quite well for me. The pieces are NOT cylindrical, but generally are approximately 4 mm x 8 mm x 2 mm, with considerable variation in each dimension.

[Gary Hair]

So here is the scenario:
I have a DCS UV printer and print on a lot of anodized aluminum. This requires an adhesion promoter and it is VERY stinky! There is no way to do this outside and it's intolerable inside and takes a while to dissipate even with two window fans drawing it out of the room, that's not really an option in the winter, I'd like to keep the heat inside where it belongs... What I'd like to do is have an air filter running to scrub the smell. I have thought about a range hood with a carbon filter, one over the printer and one over the application area. I thought about a "grow" filter but I'm not sure how well they work. I also thought about building my own filter like the ones in this thread.

My questions are about the effectiveness in general and also how enclosed I would need to keep the printer and application area so that it actually works, no use having the fumes escape around the sides of the filter. Has anyone here done something similar?

Thanks for any suggestions and advice.

[Dan Hintz]

My questions are about the effectiveness in general and also how enclosed I would need to keep the printer and application area so that it actually works, no use having the fumes escape around the sides of the filter. Has anyone here done something similar?

Throw a blanket of plastic over the whole mess, with the intake to the DC/filter at the rear, leaving the front uncovered for access and makeup air. Literally, just a piece of painter's plastic thrown over it all, nothing fancy. The high airflow of the DC should prevent anything from escaping to the side. It's a short-term setup, right?

[Gary Hair]

It's a short-term setup, right?

This is, hopefully, a very long term setup. I run parts almost every day that need to have adhesion promoter. I ended up buying a filter from Costco, it has a hepa filter, a silver nano filter, charcoal filter and something else I can't remember. It was $180 and for the time and materials to build something else I had to give it a shot. If it doesn't work then I'll return it to Costco and continue with the build.

[Brandon Tippets]

First and foremost I want to thank Dan for posting his filter build project here. We recently purchased an Epilog 120 watt Fusion Laser Engraver. Great piece of equipment. Having never owned or operated a laser we quickly found ourselves in need of a way of removing the smell and harmful vapors from our exhaust, which is routed outside. I contacted the company that sold us the laser and they sent me some information on the BOFA filtration units. I couldn’t stomach the replacement filter costs, but it was suggested that I may have to build ‘pre filter’ before the filtration unit anyways. Then I was forwarded a link to this thread.

The company that I am in partial ownership of also has a Komo 508 Mach 1 cnc router. I found an old scrap sheet of a vinyl coated plywood and start doing the layout in ACAD. My goal was to build a box that would sit behind the laser, be easy to access, and to quickly see what was going on inside the unit. We just hooked it up today and the filter is working perfectly.

We vector cut .118" thick clear modified acrylic sheet about 1 to 2 hours a day and our neighbors from nearby shops were starting to complain about the smell. (The modified portion of the acrylic sheet is the additive of rubber to make the sheets/parts stronger. And also makes it very stinky to cut.)

Here are some pics from along the way.


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I hope the pics come through okay. this is my first post. Awesome community you guys (and gals) have here. Lots of good information.

[David Somers]

Brandon,

What kind of fan are you using to move the air. Looks like it is located outside that room somewhere?

Dave

[Brandon Tippets]

Brandon,

What kind of fan are you using to move the air. Looks like it is located outside that room somewhere?

Dave

Dave,

Its a 10" in line fan that is rated at 1000CFM. When we bought the laser it came with it. The exhaust behind the laser goes straight up and through the roof (about 20 feet up). The air is being pulled through the filter and is noticeably slower in removing the smoke from the cutting area, but I have a layer about 3" thick of activated charcoal in there now. My next charge I am going to go 2" and see if that is a better balance.

Brandon

[David Somers]

Thanks Brandon. Looks like a nice job! Good luck with the new Epi too!!!

Dave

[Jacob Davalos]

Brandon,

what you need is a blower with more static-pressure "moving power". While inline fans are rated at 1000 CFM, they have very weak static pressure capabilities.

The filter adds a lot of pressure to a system that the relatively weak inline fan fails to overcome. You also have a lot of running duct. You could buy another inline fan and put both inline. While this will not increase CFM, it will increase your static pressure capabilities. Or you could buy a dust collector type of blower and easily triple your static pressure capabilities. When i say triple I mean that your inline fan will do no more than 2.5" WC while a dust collector does 8" WC. If you look up "atmosphere vortex" doing ye ol' googlefu they have a good graph in their showing you the declining CFM relative to the Static Pressure. For a 12" inline fan that at 0" WC pulls through 1000+ CFM, at 1.5" WC it only pulls around 388 CFM. I do not know how to calculate your static pressure, but there is a way - I am sure you have more than 1.5" WC of static pressure with all that piping and 90* bends and the filter.

You do not want to decrease the filtration, as in making your carbon bed 2" instead of 3" - you want to increase the ability to pass air through as thick a carbon bed as is logical for your given application.

Your design is awesome, and with a better blower, you will be good to go I believe.

[Dann Ernstsen]

Could a vacuum cleaner be used as a fan?

[Brandon Tippets]

Brandon,

what you need is a blower with more static-pressure "moving power". While inline fans are rated at 1000 CFM, they have very weak static pressure capabilities.

Your design is awesome, and with a better blower, you will be good to go I believe.

Thanks Jacob,

I have been skeptical of the inline fan since I started designing this unit. It was already in place so I gave it try (and we own it). Having never built a unit like this I wanted to make it sure it worked before I started modifying ducting and fans/blowers, ect. And I am by no means an expert when it comes to air flow so your information above is very much appreciated. I am confident that we aren't done modifying this set up.

It sounds like with a blower it would be easiest to vent back into the shop?