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post #1 of 55 Old 04-30-2008, 04:21 PM Thread Starter
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Exhaust Fans

These are the best accessory any indoor smoker can buy. Ozone generators, Hepa filters, Ionic breezes, etc are nice little add on's for freshening up, but there is no substitute for eliminating the smoke from your environment before the particulate can settle or stir around.

Exhaust fans are rated in CFM - Cubic feet per minute and sones - their relative loudness. These are the 2 important specs to consider when looking at one for your application.

CFM is the real issue in gettin the smoke out. If you have a 10 x 12 room with 8 foot ceilings that is 960 Cubic feet of air. My personal experience has led me to a simple calculation for this size rooms needed "actual" CFM.

1 smoker - 200-300 cfm
2 smokers - 450 cfm
3 smokers - 600 cfm
4 smokers - 900 cfm

Needed being defined as keeping the room from getting nasty.

A typical bathroom fan is 100-150 CFM rated. This can be deceptive as this is "at the fan". If you have long runs of exhaust lines it can dramatically reduce the capacity.

Larger fans can be loud so you need to consider this in your decision. Some of the best solutions are "inline" a fan that can be installed closer to the outlet and 4-6 feet outside of your room buried in a wall or crawl space. These can dramatically reduce the noise. It's important to pay attention to the duct sizing. Getting a high CFM fan (6-900) and installing it with too long a run/too small of pipe can drastically reduce the effective CFM exhaust you get.

Simple solutions can be cheap and very efficient. Window fans do a great job and you can pop them in and out as needed even in winter months.

One consideration seems counter intuitive but makes sense once you think about it, the need for make-up air. If your room is very tight, little egress area for air to get into the room from other parts of the house, you may get drastic reductions in the CFM performance of the fan. Assuming you get a fan with a large enough CFM, your room will go into a "negative pressure" state. This means it wants to draw air from any place it can. Typically this will be through your door cracks, outlets any openings in drywall or ceiling that go to open airspaces in your house. This is the desired state to prevent smoke from getting anywhere else in the house. Get a large enough fan and you will need to either have a damper to open to the rest of the house to get fresh air, or will need to leave the room door cracked a bit to ensure enough make-up air to keep the fan running at peak performance.

Another issue is the existing heating and cooling ducts. Cold air returns are the enemy of a good smoke room. The furnace typically has enough CFM to overcome most fans. What this means is when the A/C or Heat is running your room goes from negative pressure to positive on the returns sucking smoke back into the hvac and distributing it around the house. Blocking the return is a must when you are smoking. I use a garbage bag with a drawstring on the one in my office as it's easy in the drop ceiling. When running my exhaust and when the hvac is not running it inflates like a balloon (negative room pressure). When the hvac comes on it deflates (positive room pressure at the duct due to the cold air furnace power). Closing the heat/cool ducts and relying on the air from the cracked door for fan air make-up has been the "right" solution for me.

Anyway, think of a fan purchase like a humi purchase... it's pretty hard to buy one that is "too big".
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post #2 of 55 Old 04-30-2008, 04:37 PM
 
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Re: Exhaust Fans

Heck of a post, Dave. Any particular fan recommendations? Retailers?
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post #3 of 55 Old 04-30-2008, 04:53 PM Thread Starter
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Re: Exhaust Fans

Quote:
Originally Posted by croatan View Post
Heck of a post, Dave. Any particular fan recommendations? Retailers?
http://www.fantech.net/inline_duct.htm

I got the 750 cfm one for my home office/smoking room. On a variable rheostat so under normal circumstances it is very quiet at a lower speed.
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post #4 of 55 Old 04-30-2008, 07:08 PM
 
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Re: Exhaust Fans

Excellent post Dave. I have a 12x20 room in which my 300cfm exhaust fan is adequate for 2 smokers. It starts getting kinda nasty with 3 smokers but manages to keep any smoke from entering the rest of the house (the beauty of that negative pressure you mention).

I have sealed off my cold air return completely and rely on gaps in the door frame, closet and false ceiling for makeup air. Probably need to consider a heated makeup air duct for next year. I chose a relatively low cfm to balance my need for exhaust with the need to pay high heating bills.
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post #5 of 55 Old 04-30-2008, 08:19 PM
 
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Re: Exhaust Fans

Thanks for the info Dave. My roommate (next year) and I are considering building a smoking room in our dorm room to stick-it to the Indiana winters. This looks everything we would need to know about ventilation :tu Now it's just the insulation that we need to figure out.
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post #6 of 55 Old 05-01-2008, 12:35 AM
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Re: Exhaust Fans

I'm currently working on a room 15' x 12' and went with a 600cfm exhaust.
The reason being that I can get away with using >9" duct work. The 12" would have been imposible for me to use(common with larger exhausts). You need alot of clearance for 12" ducting.
http://www.ventingdirect.com/index.c...h&keyword=HLB6
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post #7 of 55 Old 05-01-2008, 11:38 AM
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Re: Exhaust Fans

Rudder,
That unit you have looks huge, what are the dimensions. I was thinking of going with the inline type unit, that looks much smaller and easier to install remotely.
Fantech makes a composit inline unit that can be installed outside. I was going to install it under the deck with the intake vent in the basement.

Dave

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post #8 of 55 Old 05-01-2008, 01:54 PM
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Re: Exhaust Fans

Quote:
Originally Posted by SouthsideCigar View Post
Rudder,
That unit you have looks huge, what are the dimensions. I was thinking of going with the inline type unit, that looks much smaller and easier to install remotely.
Fantech makes a composit inline unit that can be installed outside. I was going to install it under the deck with the intake vent in the basement.

Dave
12"x22"x12" It actually isnt all that big.
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post #9 of 55 Old 05-02-2008, 06:16 AM
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Re: Exhaust Fans

Just my here.

I have a room that is 12x15x9 and I have installed a 6" inline fan to extract the smoke in this room. One of the things I would like to add is that I have also added a 4" air vent with back flow protection.
So here is how it works. When I turn on my inline fan it opens fresh air intake and all stale (Cigar Smoke) is exhausted. One of the things I figured out this winter is it gets cold so I have found the cure. I installed a 1000 watt heater made by Omega that is 4" round AHF10120 and heats the cold air from outside. I don't have pictures of my set up seeing it is behind the walls and in my ceiling. But I will add pictures of the units and list the website information.
BTW that is not the only heat I have in the room. Also have a 240V Cadet wall heater.
This is just what I did. Not saying everyone needs to do that but fresh air is a must to make sure you can extract all stale (smoke) from your room.

http://www.omega.com/ppt/pptsc.asp?r...TER&Nav=heaj01 (Heater)
http://www.rewci.com/fa6392cfminc.html (483cfm 6" fan)

James
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post #10 of 55 Old 05-02-2008, 02:02 PM
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Re: Exhaust Fans

Would placing 3 300 cfm fans in a room be the equivalent of a single 900 cfm fan?

Now you know,
and knowin's half the battle.
- G.I. JOE [SIGPIC][/SIGPIC]
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