[fantasy2]

Hi all,

Just relocated my laser to my garage with fume extraction to the outside but the smell is unbearable for my neighbors... So I build a fume extractor, based on results from others.

The size of the extractor is 700x400mm(27.5x16 inch) and contains a 5cm(2 inch) thick layer of active charcoal from the fish pond store.

For some reason, there is still a smell and visible smoke. Did I buy active charcoal that is too coarse? Or does active charcoal not filter the smoke out and do I need to add something like a hepa filter?

Anyone experienced with making a DIY filter?

[andrewmb]

Professional filters usually have a pre-filter for large particles, followed by HEPA for small particles and then the charcoal bed. Activated charcoal bed is usually 5+ inches deep. I've heard of several people trying to make a home made one and running into the same issues. So far as I know no one has made a home-made one that works well.

[Bec Weir]

I was lucky enough to be given an Austrian made HEPA filter by a special effects company who just waned to get rid of the bulky filter from their store room.

It has a large paper pre-filter which is about 20cm deep of corrugated paper and TWO carbon filters that are 30cm deep each. I replaced the carbon with 5mm cylinder activated carbon from an aquarium supply store. All up, I used 50kg of carbon for the filters.

The paper filters I just vacuumed and then blasted with compressed air (outside of course) to clean.

It takes a hell of a lot of oomph from the two blower/suction motors to draw the cutting gasses through such a large volu e of pre-filters and carbon, but the resulting air from the HEPA is just mildly scented of the activated carbon.

TLDR version: you need a pre-filter, more depth of activated carbon and strong motors to move the air through the filters.

[fantasy2]

I copied the idea from people at sawmillcreek that made a fume extractor. Took the same dimensions and thickness of charcoal that worked for them. Maybe there are still holes somewhere for the smoke to go through without going through the filter(I placed the charcoal in 4 bags and stacked them).

I do not have a HEPA filter(couldn't find one).

What is the exact function of this filter? Maybe the charcoal works and removes what it has to remove but without the HEPA filter it still emits smoke & smell?

[Bec Weir]

The paper filter is first topped with a synthetic fibre mat, which catches all the large stuff; It gets quite dirty. The paper filter, from what I was blowing/vacuuming out of it, catches the finer stuff, but does still let some particles through, as there is a VERY fine powder (and it is only a dusting after months of work) on the carbon filled boxes underneath the paper filters.

I think the carbon gets rid of the volatile gasses and the stink (which is probably caused by the same thing), and sweetens the exhaust, which I vent out of a window of my workshop.