I share your concern here. I have one of those roof-mounted industrial exhaust fans that could suck the eyes out of a parrot (old Tim Allen comedy reference). I’m worried about pulling too much air through the exhaust port of the GF. I emailed the GF team early on with this concern and Dan responded, “I don’t believe it’ll cause any harm. We haven’t tested with it but eyeballing the unit there’s nothing that should cause trouble.” I might have to implement some sort of valve that I can adjust to draw in additional room air along with the GF exhaust to lower the suction on the exhaust vent. Thanks for the link. That was good reading.
Thanks for the info. I’m going ahead with the dust collector and will make it work. I’m not sure if your roof mounted fan is hardwired but if it’s a plug in harbour freight has this speed control which will make the air regulation easier. http://www.harborfreight.com/router-speed-control-43060.html
This industrial fan is intriguing to me. What kind is it? I’m interested in setting up ventilation for my basement lab/lair/office/cave, and in the event I encounter any parrots that need their eyes removed, I’d like to see what my options are.
I use a Nutone RF-40 roof-mounted exhaust, which was installed back in 1995. Here is a description: http://phacproducts.com/nutoneparts\RF-40.pdf I believe it is a discontinued model these days, but there is probably something similar available. It is rated 1000 CFM.
Cheapest IKEA kitchen ventilator is $69 and a replacement active coal filter is $10 I think. Who will do the first blueprint and print out an external filter? 
Edit: its $119 for a fan that can support an active coal filter.
Your typical bathroom fan only moves about 100 CFM. I have a dust collector for my wood shop that is rated at 1200 CFM. Similar to this: https://www.pennstateind.com/store/DC2V3.html
Rockler hardware and WoodCraft stores have dust collection for woodworking that would be more than adequate. If 1200 CFM is too much, you can put a “Y” connection on the intake to reduce the air flow.
IMO you don’t need to over-engineer this.
1000 cfm is serious overkill. We run ~750 cfm on a cutter 4 times the size of a GF. Remember, dust collectors need extra lift to move heavy wood chips and fine dust, typically upwards of 5+ feet up into a duct system against gravity. You’re probably moving mostly fumes horizontally out the door so 400 cfm should be plenty. Recommend a hurricane fan for exhaust…they’re powerful and very quiet.
I’m also interested in how much “suck” you can put on the exhaust fans of the GF (regardless of whether or not it feeds a dust collector). Someone mentioned setting it up on squirrel cage and then there is this photo from (http://www.instructables.com/id/How-to-Use-a-Laser-Cutter/?ALLSTEPS) that shows a similar set up for an Epilog.
At what velocity of external venting will the GF exhaust fans be damaged?
Speed control wil seriously reduce the life of your motor - I really would caution you to do a little online searching and you will see what I mean. You need to use some sort of mechanical air flow restriction - like an air gate - and it wont cost you any more than the speed controller would.(http://www.amazon.com/Dust-Collection-Plastic-Peachtree-Woodworking/dp/B000H555B2) You also are going to need to find out what the max air draw is possible without drawing to much air from the Glowforge. You should simply find out what the dust filter fan OUTPUTS. Then you will need an airflow meter - hold it in front of your draw and adjust your gate until you have the correct air draw.
Thanks Tennessee… I came to those same conclusions the last couple of days as I’ve been planning out my system. I need to install air gates anyway so it was pointless to install a speed controller. I found a couple of cheep sources for manometers and i’ll just mark the location on the air gate that works.
@Jamie Would you be willing to share you sources of cheap manometers?
@Tim I’ve had experience using a squirrel cage fan with an Epilog. Having the fan in the same room as the laser has two main problems. 1) It is extremely loud. 2) It develops a high positive pressure between the rotating fan and the outer housing that leaks quite a bit into the room. If you put your hand up to the housing, you can feel all the contaminated air leaking out. After an hour of cutting, it would get so bad that I would have to leave and air out the room. Two solutions are: 1) put the fan outside (probably not feasible), or 2) build a box around the fan and connect the vent hose from the laser to the box. A negative pressure will develop in the box to pull air through the hose, and also vent any leaking air from the fan. This will also help with the noise problem. Like this:
@tennessee_reid I wasn’t aware of the dangers of a variable speed control. I use Nutone’s CFVS-1N speed control with my roof-mounted fan. It’s the one Nutone recommended. (http://www.electronic-circuits-diagrams.com/store/Cfvs-1n-Nutone-Whv-20-Ventilator-Variable-Speed-Control_371455335446.html) Do you believe this one is dangerous to use as well?
I’m starting to plan the layout of the area where I will eventually put my GF. I haven’t seen any pictures of the location of the exhaust port. Does anyone know where it is located? I want to orient the GF so that I can pass long materials through the slot easily, but don’t want to have the exhaust duct in the way.
Just a word of caution, this type of speed control only works with a brush type motor, such as in routers, drills and angle grinders. Adding a “y” or “t” with a blast gate in your duct can also help control your airflow by restricting how much it draws from the Glowforge.
@Fan - I can’t speak to it’s effectiveness yet. I’ve ordered one and will post on here if it works. This is where I ordered from though - Aliexpress
When you face the front, it’s near the left edge on the back. I can take a tape measure to it when I’m back at the office.
I just wanted to add, that a dust collector will not filter the fumes from the laser. You still want to filter those fumes through a charcoal filter, or vent them outside.
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Here’s a good quality remote switch for a heavy duty fan (also available elsewhere):
http://www.leevalley.com/en/wood/page.aspx?p=67020&cat=1,42401,72660
@Mike_C makes a good point. about fumes. A further caution - my understanding is that charcoal filters primarily reduce odor, and depending what you are cutting, may do little or nothing in terms of reducing dangerous gases.
If we have a unit with an air filter can we run it with the hose as an option or are we going to be committed to using the filter unit?
It’s an option just plug in the hose and you’re good to go is the plan. Dan mentioned in another thread but I can’t find it quickly.