Can't find source of Laser Exhaust Smell

[Aaron Litten]

Pictures attached for context (pardon the mess as we just installed this recently)

Some background:
-Bought a 105w Boss laser (LS-2440) as an upgrade from a Glowforge Pro to cut 8mm Bamboo Plywood

-Used the 6 inch exhaust fan that came with the unit but smoke poured out of the fan housing so we bought a Cloudline S6 In-Line fan rated at 400cfm (give or take).

-That Cloudline fan also leaked smoke like nothing else so I silicone sealed every crack or opening in the housing and it no longer leaks as a source of smell.

-The current material (8mm Bamboo plywood) technically covers the whole cutting bed but our process is to cut one product out as a vent hole for the exhaust to pull through then batch cut the rest.

-Each time I cut anything on this machine, even if the bed is wide open to pull the smoke down, the exhaust somehow fills the room with strong smells.

-There is no visible smoke but our air quality meters are showing high particulate and VOC counts.

-The room this laser cutter is in is connected to large warehouse space with plenty of make-up air.

-The Exhaust has a vent cover to prevent animals from crawling into it while still allowing a large volume of air to be pushed out.

Main Problem:
-We are looking to scale up to using this laser machine for about 6-8 hours a day and need to track down the source of the exhaust leak.

-If I put my nose to every "crack" in the building I smell nothing being pulled back into the building.

-Regardless I've sealed every crack I could to prevent this issue and yet it persists.

-My next step is to get a 1000cfm+ blower and get a 15ft vertical exhaust stack outside because I'm at my wits end.


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[Kev Williams]

If the blower is INSIDE and not outside, if possible move it outside! The ductwork FROM and inside-blower to the outdoors is under POSITIVE air pressure when the blower is running, and if there's ANY place whatsoever between the blower and where the duct exits the room/building that's leaking even a little bit, smoke and smell WILL be pushed into the room. With a blower OUTSIDE, all air within the ductwork INSIDE will be in a vacuum condition; so if any leaks DO exist, they will draw room air INTO the duct and move it outside...

[John Lifer]

If the blower is INSIDE and not outside, if possible move it outside! The ductwork FROM and inside-blower to the outdoors is under POSITIVE air pressure when the blower is running, and if there's ANY place whatsoever between the blower and where the duct exits the room/building that's leaking even a little bit, smoke and smell WILL be pushed into the room. With a blower OUTSIDE, all air within the ductwork INSIDE will be in a vacuum condition; so if any leaks DO exist, they will draw room air INTO the duct and move it outside...

I'm late, but Kev is totally right. PLUS the cheap inline fans LEAK like a sieve themselves. They are NOT good to use for laser cutting at all. I've got a 6" that I have hooked up to my fiber lasers and the fan is outside. But they do NOT like any backpressure. And for a CO2, the chinese centrifugal blower or a harbor freight dust collector outside is the BEST option for pulling air and smoke out......

[Dave Garrett]

You'll want at least 1hp dust collector with solid metal ducting (no right angles) taped down every seam and junction. Theres plenty of threads on the subject here that helped me build my system. The in-line fan isn't going to do it.

[Mike Null]

I have been using a 6 inch inline fan for more than 20 years. If it ever dies I'll replace it with the same thing.

[Bill George]

Ditto to what Mike said, seal All the joints and exhaust outside very far from the building or to the Roof.

[John Lifer]

I have been using a 6 inch inline fan for more than 20 years. If it ever dies I'll replace it with the same thing.

I'll GUARANTEE that if your fan is 20 years old it is NOT the same quality (junk) plastic fan that it seems everyone is selling or providing with the new lasers.
These fans are cheap plastic MJ grow fans that only boost airflow. they don't work with any back pressure. I've a 6 inch one that I bought for use with my fibers. It works, but leaks like a sieve.
I ended up putting it outside and it will pull most vapors out. but it is NOT equivalent to the metal chinese blowers or a HF dust collector blower.
I see more complaints about smoke with laser use than anything else and 99.9% is due to lack of flow OUT.

[George Yetka]

The way your fan is right at the wall. The only way it would be the cause is if it were too week or if the seal to the wall was bad. You can hold a lighter to the joint and move it around to see if it flickers. If the hose before the fan were leaking it would be sucking air in not pushing it out.

The next issue may be the door seal on the garage.

[Mike Null]

The only place my USA made inline blower can leak is at the points of installation (top and Bottom). I installed it along with my SIL and it doesn't leak. I can also stand next to it and carry on a phone conversation.

[Kev Williams]

I'd still say that motor needs to be outside. AND, your vent exit is too close to the window and garage door, easy for smoke & smells to drift in...

Here's my jerry-rigged setup, which exhausts the 2 C02 and 2 fiber lasers in my garage shop, 1 C02 and 1 fiber each share a blower, separated by Tees and blast gates to 'steer' the suction...
Outside the garage window is this 'patio box', which I semi-unearthed for these pics, which are pretty grainy as it's pretty dark out, no flash so I artifically lightened them up, but oh well!
blwrbox.jpg
--note the 2 intake hoses coming down out of the garage window... also notice the 4" hole on the front-right side of the box, there's another one on the left side under the tarp, those holes are right next to the blower's motors cooling-air intake, so the motors never overheat. (I just make sure the tarps are away from the holes a bit.) Inside the boxes I've stuffed fiberglass insulation around everything EXCEPT the blower's motor's proper, for sound abatement...--the exit hoses come out the left side, not seen in the photo above, curl around and run behind the box along the ground, about 15' away from the main box and into these home-made filter boxes, which are just storage boxes with a securely lockable lid--
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air is pushed into the boxes, and exits the other side thru a 4" hole- note the old furnace filter standing next to the right side of the boxes- That's just for good measure

INSIDE the boxes--
chrcoalbox.jpg
Is some 1/2" square hole wire screen to hold everything in, a basic furnace filter on the left side, again just for good measure, and the rest of the box is filled with one of the large bags of el-cheapo charcoal briquettes Walmart sells. Those briquettes ARE as grungy as they look, I need to change them out, they've done their job!

It's not perfect, but not once in 8 years has a neighbor complained, or even noticed (and I've asked!), the teensy bit of hum coming from both motors, even late at night (the fiberglass works), and more important, no one has ever said they've smelled anything. If you're standing right next to the charcoal boxes, you can sometimes see a bit of smoke, or smell the Rowmark or wood or whatever burning, but once you're 20 feet away, you can't see, hear, or smell anything- unless you're trying to!

My garage shop does smell of what the lasers are doing a bit, but it's never more than minor, the smell never ends up in the house, because any and all air moving thru the vents is in a vacuum condition, meaning all 'static' air in the garage is also in a vacuum condition, which removes air FROM the house, rather than pushing air INTO the house... And once the engraving stops, any leftover smells clear within a few minutes.

[Aaron Litten]

I appreciate everyone's feedback. I'm going to see what actions I can take before diving deeper into moving my entire unit and cutting a new hole for a new machine location. I won't be able to take any advice with pictures because I'm weird about online payments for forums and security in general.

[Aaron Litten]

Alright everyone, I made the changes (to a blower fan on the outside of the shop) and it seems like the smoke is still escaping the enclosure. I smell it coming out of the cracks in the lid now. Are Boss lasers that poorly designed that it can't provide good makeup airflow to get rid of the smoke?

[Mark Sipes]

Go to MeterMall.com and purchase "smoke generators" Regin Smoke Emitters

$13.95 -- Dense white smoke for airflow and leak tests. Range of burn times and volumes..

Purchase smoke generator (best suited for your needs) and place in at furthest point on table where the laser would travel. Turn on laser as if to run a job. Fans "On". Light (fire) generator and close top of laser as in running a job. Check machine box for leaks ...mark with markers (blue painters tape) Check the entire exhaust system... pipes, connections and fan area. Might need a few people to help dependent on length of plumbing and smoke burn length.... Seal the leaks and repeat as needed.

Remember the further you move the fan from the machine the less efficient the fan becomes. This is due to the inner surface of the exhaust pipes placing surface resistance on the traveling air and slows the amount of air CFM permitted to exit the laser box........ Even with an efficient system the pipes should be cleaned weekly/monthly/yearly based on the materials being lased /cut. If the pipes have build up... so do the fan's blades....



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