Cheap alternative to carbon filter??

I have seen people talk about things you can put in your duct to neutralize the odor of the air going past it from your inine. Has anyone heard about anything like this, that could be a cheap alternative to a carbon filter? If so, what is the life expectancy compared to the average carbon filter (which I heard was about a year and a half depending on brand)? I need to get rid of the smell of about 6 or 8 strong plants from a grow tent, I wana blow the air straight out my 3rd floor window.

thanks man

carbon is your best bet, other stuff masks, carbon doesnt just mask

yea im seein that carbon is the only way to go, now its about finding the cheapest one that is effective for any amount of time, any suggestions? The very cheapest one for the 6" 530 cfm inline im getin is around 80.

You could always check out this thread here. Very cheap carbon filter for smaller grows and if it doesn't completely mask the odor just install a second one. The OP of that thread claims he made his for $10 so that's a very cheap alternative to commercial filters.

im considering a diy, but if i bought a good one and used it the 2 years or so, couldn't i just replace the carbon with cheap refill and change the prefilter?