One more Venting Question

Apologies if this duplicates previous posts…

I am finally going to set up my GF basic in the next day or two (recently moved, and there’s some stuff that has to be moved out of the way before I can unbox). It’s in a basement, and will be pretty close to a very simple overhead kitchen fan that has no big fancy housing on it - it’s just a circle above the stove with a van unit inserted into it.

Any thoughts on using that to vent (with the kitchen fan on or off), rather than running a longer tube to the nearest window until the filters come in? The basement kitchen isn’t being used as a kitchen, so it’s not getting in the way of that…


A lot of kitchen vents don’t have the CFM rating to handle the output of the GF. Conventional wisdom says that the GF does about 200 CFM, though i am not sure if that has been officially stated or tested. I’ll assume you won’t be able to seal it to the kitchen vent, so you’d want your kitchen vent to be WAY more than 200 CFM to be sure you suck up all the errant GF fumes.

Personally, I’m not sure I’d even do that, I am a proponent of cutting a dedicated dryer vent for it, because even a small gap will lead to a ton of smell. A dedicated vent is the best solution to keep the fumes from creeping back in around your window.

We’re so excited to see what you create with your new Glowforge! Thank you @evansd2 evansd2 for your answer, as well.

Your Glowforge is designed to operate with the included exhaust hose connected to the outside with a maximum of two 90 degree bends. If you configure your exhaust differently, the Glowforge unit may not be able to expel enough air, and it could cause smoke and fumes to enter the room. Because ventilation is complex and poor ventilation could cause smelly and even dangerous results, we can’t advise on exhaust configurations other than what’s described in the Glowforge Manual.

If you do want to configure your exhaust differently, there are some great resources on the forum that can help. I’m going to move this post to the Beyond the Manual section of our community forums to see if the community has suggestions. Note however that advice in this section is unsupported and is not reviewed by Glowforge.

The longer the tube, the greater the “pumping loss”. The tube presents resistance to the flow of air through it. The longer the tube the greater the resistance. Since the fan tries just as hard to push air regardless, higher resistance from a longer tube means higher pressure in the tube which means it’s more likely to leak. From your description it sounds like you could plumb in to the fan duct with one 90º bend. But if the run from the vent inlet to outlet is long, this may be a problem. If there’s a fan in the duct, running it would help. But most kitchen fans aren’t very high CFM so it might not help enough.

My vent setup is slightly longer than 8’. But I have a 220CFM fan in-line at the end of the 8’ duct, that discharges into the vent tube that goes through the wall to the outside. When I run the GF, I also run that fan. It’s sucking about as hard as the GF is blowing, so it does a good job of compensating for the long tube. It basically makes the tube “look” as if it’s much shorter.

I tried: Airflow measurements

From the part number and specs that @scott.wiederhold pulled in his tear down, it looks like the fan is actually rated at 190cfm (at the fan). As you mentioned in your post, your loss seems inline with that (and reasonable loss for the set up).