Exhaust filter box in-line with 4" duct

[Billy Royse]

We will be exhausting through the roof with 4" metal duct with a HF Dust Collector. We are concerned about the smell outside from the Rowmark plastic we are engraving. My idea is to install a furnace filter box in-line with a section of the 4" Straight duct that we have access to. We could then open the box and insert either an off-the-shelf carbon furnace filter or a DIY Carbon filter. I would then seal up the door with the metal duct tape and just cut it open when the filter needs to be changed. I'm not looking for "smell free", just enough to keep the neighbors from complaining.


http://www.airclean.co.uk/1825_Duct_Mounted_Filter_Box.htm



What does everyone think?

Thanks for the help.

[Kev Williams]

I've been exhausting 2 blowers for 12 years and a 3rd blower for over a year in our neighborhood, no one's complained yet. Gets pretty smelly near our house, but it seems to dissipate quickly.

However, my exhausts are at ground level. My BIL vented his laser (he cuts only wood) thru his roof, and his neighbor told him he could smell it when he ran his swamp cooler.

Right now I have my 2 older blowers exhausting thru a pair of expensive furnace filters. They don't do squat for stopping the smells...

[Glen Monaghan]

I don't believe that any off-the-shelf "furnace" filter, carbon or no, will do diddly squat for the odors produced from a laser engraver. Too thin and nowhere near enough carbon to have significant effect, given the greater volume and speed of air being drawn from the laser compared with an HVAC system.

[Ron Philman]

True, I've been around 4 or 5 stage filtration / fume extraction systems with lots of carbon, HEPA block filters and
prefilters that worked. They had variable speed exhaust fans as well. Except laser cutting acrylic- there was still some smell.

[Billy Royse]

Thanks for the response!

[Dan Hintz]

Bill, see my blog post... air is moving fast, so you need some thickness/surface area to the filter.