I was thinking of putting together my own carbon filter.. something along the lines of having a 2 furnace filters with powder carbon inbetween them.
Anyone done this before? Plans? Also, where would one be able to buy activated carbon by the lbs/kg in Canada?

The carbon is in pellets , not powder. I have seen such setups , and they do work , but the price of a filter is not much more than the price of the carbon , so ........

I like to play it safe , and use a professionally made filter.
Yes many stores in Canada carry 10 pound Boxes . I get mine at Jons Plant Factory , on East Hastings St. Burnaby ( Vancouver)

I've got to ask....
In what way "safe"?

I'm pretty sure that a bulk bag of aquarium charcoal and the homemade filter fix is probably cheaper.

i use a five gallon bucket with a six inch duct insert on the lid and holes drilled in the bottom.i buy a 3olbs bag of activated charcoal for 90 bucks.it has lasted me for over a year now and i still have over 20 lbs.works well!i would consider that pretty cheap!

Crap happy... where did you source 90lbs? Thanks..

Or you can use carbon filter that looks like a roll of felt and some type of reinforcement mesh like chicken wire inside the metal pipe and around the exit end. Cost about 70 dollard total setup

All you need is a couple of A/C parts to build a great carbon filter, and the cost is about 35 dollars to build it. After your initial cost its about 15 dollars to refresh it.

Here is what you need.

Purchase a 6" piece of A/C duct coupling material, and a 6" cap (you can even use PVC for this if you want even less expensive) a bit of that small wire mesh and an activated carbon A/C filter.

take the wire mesh and cut it into a strip about 10 - 15" wide and at least 15 - 20" long (you will need it to be long enough to wrap around the other pieces). Now, wrap the wire mesh around the A/C coupler or PVC so that it covers an inch or two of the coupler, secure it with duct tape or aluminum tape. on the opposite end of the wire mesh you will be inserting the cap you have as well and securing it the same way.

Now you should have what looks to be a tube with one end open, the other closed by the cap and the wire mesh all wraped around to make it a tube.

That Active carbon A/C filter you bought, cut it up. all you want from it is the carbon cloth that is inside, usually enough to make 3 - 4 of these things. cut the carbon filter material into a length that will completely cover the wire mesh and wrap all the way around the tube. Now all you have to do is take more duct or aluminum tape to seal off both ends of the carbon sheet on your tube. this makes it so that all of the air passing thru must pass thru the filter material and cant leak out around the edges.

And there you have it, one great carbon filter for about 30 - 40 dollars. Nicest part of this filter is that after 3 -6 months all you have to do is remove the used carbon sheet from the outside of the tube and replace it with the leftover material from when you built it or at the very worst go and buy another A/C filter. They only cost about 15 dollars.

No muss, no fuss and everything is readily available at your local home improvement store.

I guess what I mean by safe is....

A good pre made filter is about the price of an Oz or an Oz and a half , and smell is a good way to let the neighbourhood know what yer up to. I would rather trust the manufacturers specs , and know that I have a good year of useage , rater than the unknown life expectancy of a homemade filter. Another factor is that the filter may be effective when you are outside , checking for odour , but when you are in the room tending , and moving/bumping plants , they seem to release more of their perfume , but you don't know , because you are inside at the time (I'm speaking from experience here) . A good idea , is , if you have a partener , or wife , or confidant , get them to be downwind from your filter , while you are tending your garden ,just to make sure that it's effective....

http://www.hg420.com/showthread.php?t=14118

or

http://forums.mycotopia.net/showthread.php?t=8038&highlight=carbon+scrubber