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DYI Odor Control System

ww4727

New Member
Today is just an overview:

I am starting this thread as I build an affordable Do It Yourself Odor Control System. I have done this on large scale for wastewater treatment plants there are basically three primary methods to scrub odors out of air. 1) A Carbon Filter, 2) A Wet Scrubber, and 3) A Biofilter. All three have their place and can do a formidable job.

A carbon filter adsorbs (not absorb google the two words to see the differnce) the odor onto the surface of activated carbon particles. As the carbon fills up, the ability to adsorb becomes less and less. This is one two primary reasons a carbon filter fails over time. The second reason is that the air passing through filter develops a preferential path, a short circuit so to speak. When this happens much of the filter is left unused. The small fraction that is used gets blinded as noted above and the filter fails. One problem with carbon is once the surface area is consumed through chemical adsorption, the filter can no longer stop odors. Unless a regeneration system is used, the carbon must be disposed of and replaced. I dont recommend most people try to regenerate their carbon as it involves the use of acids and can be dangerous if not handled properly. So toss it and buy new, it will be less expensive than the hospital bill for chemical burns.

A wet scrubber is very different beast. It takes various liquids and uses very small droplets to absorb and disolve the odor causing characteristics. Depending on the chemical makeup of the odors the liquids used are plain water, sodium hypchlorite (liquid bleach), and caustic soda (liquid draino). Often times these are multi-stage units that are operated in series to significantly reduce odors. The liquids are sprayed over a plastic media that breaks the water dropplets into smaller drops creating more surface area to absorb the odor chemistry. This type of system is good for very large volumes of sufide and ammonia based malodorous gasses, but is of limited value for volitial organics. It is also very expensive to build, operate and maintain.

A biofilter is unique in that it uses mother nature to scrub maloderous gasses out of the air. It consists of an organic mass (such as peat) that is kept damp at all times. The organics are effective at absorbing and adsorbing the malordous gasses. The biggest drawbacks to this is 1) it takes a large space, and 2) if it does not stay damp, it does not work. It would be a good choice if you had a large space in a very humid environment. But if air in your region gets below 50% humidity, it will struggle. I cant use it where I live.

I think the ideal odor scrubbing system for a grow room will actually be a combination of a single stage wet scrubber followed by a two stage carbon filter. My logic is as follows: The single stage wet scrubber would use water only. Water is a great cleanser. For comparison, remember what the air outside smells like right after a good rainstorm as compared to what it smelled like before the storm. The air smells clean and refreshing. Well a single stage wet scrubber can achieve part of that in a very short time. The wet scrubber will likely reduce the odor by 30 to 70% depending upon the chemical make-up of the odor and the size and quantity of the water dropplets. By using this, approach, the life of the carbon filter will be greatly extended, maybe by 100% or more.

The next component should be a carbon filter. I would recommend two filters in series as I intend to build. The first filter will collect most of the malodorous characteristics and second filter will further polish the air to make the smell even less noticable. The first filter will fail first and the second filter can still accomplish the job allowing you time to replace the filter before full odor breakthrough occurs.

I am going to describe the construction of an affordable carbon filter here because it is cheap to do and can be done relatively quickly. I am 4-weeks into a grow and my wife already smells the skunk so this weekend I am going to get it built and operational. I may add the wet scrubber in the future if it is needed or I just get creative, but for now I am just building a carbon filter.

My grow box is a cabinet in that is 18" x 36" x 36". This is 13.5 cubic feet. The fan I purchased is a low end bathroom vent fan that runs at 50 CFM. Using this fan, that will change the air in my grow box 3.7 times every minute. That much air transfer will likely be too much so I will build in a regulating valve into the scrubber. I have sealed 5 out 6 sides of my grow box. That way air only enters the box from one side and I can maintain a negative air flow on the grow box. A negative pressure is criticle to ensure all the air that needs scrubbing gets scrubbed.

I have buildt a small wooden box around the fan 8" x 8" x 12" to serve as my scrubber. I have put a small 1.5" PVC pipe in the side of the box at the bottom and connected the fan to the top. The pipe will also penitrate my grow box on the back side as air enters past the doors on the front. I have purchased 22 ounces of activated carbon from Pet Smart (find it in the fish department).

This weekend I will craft 2 screens to hold the carbon beds and a sealable access door to allow changing the carbon beds. I also intend to install a second pipe at the top of the carbon scubber to allow me regulate down the amount of air flow that I pull through the filters by letting some air from outside the box bypass the filters into the fan. This second pipe will have a small valve on it to permit regulation. The thought is that 50 cfm may be too strong on the 64 square inch carbon filter and suck the carbon out. Also 3.7 air changes per minute will wear out my carbon quicker than necessary. By opening a top valve, I can reduce the effective suction through the carbon bed to just enough to rattle the carbon bed. The reason I want to have the carbon jump slightly is to cause gravity to continually block each short circuit as it occurs. I want just a little vibration, not much more. The valve will allow me to regulate flow to achieve this.

Right now my total cost of this is: Fan $13, wood for box $0 as it is scrap, 22 oz of activated carbon $15, two tubes of silicon $5, PVC pipe $0 as it is scrap, and small regulating valve Estimated cost $5. So my total cost will be about $38 plus my time to build it.

Next week I will update this blog on the progress, sucesses, failures, and problems. I hope this helps those of you wanting to create an affordable means of odor control.
 

ww4727

New Member
Update.

Finished carbon filter. The odor was gone from room in a few hours. I used 3/4 lb in the first stage and half pound in the second stage.

The good: it works, actual cost $33, did not need regulating valve.

The bad: 50 cmf will not vibrate media. Therefore, I will stir carbon every couple of day to make sure short curcuits dont occure.

I will post pics on monday. It was easy and quick.
 

ChicagoJoe

420 Member
Update.

Finished carbon filter. The odor was gone from room in a few hours. I used 3/4 lb in the first stage and half pound in the second stage.

The good: it works, actual cost $33, did not need regulating valve.

The bad: 50 cmf will not vibrate media. Therefore, I will stir carbon every couple of day to make sure short curcuits dont occure.

I will post pics on monday. It was easy and quick.
I think you just helped me extend the life of my carbon. A new rigging is in order so I can access the carbon easier, but it is in the works.
 

Box of Rain

New Member
Sounds like a Great inexpensive way to control the SKUNKS- Please send pic's soon!
Good Job!!


"One Man Gathers What Another Man Spills"
 

ww4727

New Member
Here are the pics. Sorry about the quality, camera phone in dark has limitations.

First pic is closed filter. 12" tall, 8" wide and deep. 50 cfm bathroom fan on top. 1.5" pvc foul air suction on right bottom.

Inside of filter. Two carbon beds making it a two stage filter. Two thiner layers will be more efficient than one thick layer because short circuiting can be better controlled and failures can be identified before a complete system failure occurs.

I used reminants from an old windo screen to hold the tiers. Then I used a cheap AC filter to catch dust prior to going through the carbon. The AC filter also holds the finer carbon where it might fall through the window screen.
 
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