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View Full Version : Getting a lot of fumes, need some troubleshooting advice.



Jacob John
01-06-2018, 12:51 PM
So I've read through multiple threads on how people vent, and my current setup should be more than enough to not have fuming in my garage. Granted I have the HF 2HP dust collector, but it's rated at a high enough CFM that it should have no issues pulling fumes. Whether its acrylic or wood, we're getting heavy fume smells coming into the garage. I checked for leaks, and made a few adjustments which helped a little, but we're still getting fumes. When the extractor is running, you can see it drawing smoke, but it isn't as impressive as I think it should be.

Is it possible for fumes to be escaping the dust collector motor? Any other suggestions on what to check? I cleaned the extraction ports on the laser so I know that isn't an issue. I'm scratching my head.

Oh and for understanding, we vent directly outside.

Keith Downing
01-06-2018, 1:04 PM
Does the Trotec have air filters that need to be cleaned on the machine? Are all the fans on the machine running properly so that it's able to bring in enough air?

Are you using the correct size hose for the blower you're using to vent the fumes? Any potential leaks or tight corners that might be impeding the airflow?

Finally, where are you drawing your clean air from for your shop space? Is it possible the fumes you're venting are getting sucked (or blown) right back into your workspace?

Keith Downing
01-06-2018, 1:09 PM
Also, what CFM is your blower rated for?

Jacob John
01-06-2018, 1:10 PM
Does the Trotec have air filters that need to be cleaned on the machine? Are all the fans on the machine running properly so that it's able to bring in enough air?

Are you using the correct size hose for the blower you're using to vent the fumes? Any potential leaks or tight corners that might be impeding the airflow?

Finally, where are you drawing your clean air from for your shop space? Is it possible the fumes you're venting are getting sucked (or blown) right back into your workspace?

As I typed this, both of these stood out. I never looked at other people's setups, but in looking at a few videos, I see that the tight turns might be restricting airflow. Now, I'm not 90 degreeing the hoses all over the place, but I have a several 45 degree turns before it goes outside. How much does each turn affect the efficiency of the HF extractor?

To your second question, that's another potential issue. The laser is on the back wall, near where the fumes are being sent outside. the genius that owned the home before me sheet rocked the garage, but didn't insulate, so I guess it's possible that a small amount of fumes come right back through the wall. Should I consider venting on the opposite wall from the laser?

Jacob John
01-06-2018, 1:11 PM
Also, what CFM is your blower rated for?

I'll have to check but I think it's the 660 CFM from Harbor Freight. https://www.harborfreight.com/13-gallon-industrial-portable-dust-collector-31810.html

It is , it's this one. This might be part of the issue too. I might need to upgrade. I wonder if my local Rockler has a few options.

John Lifer
01-06-2018, 1:35 PM
OK, so I'm assuming you are using flex to the blower and hard pipe going out? My blower is outside and that is my first suggestion.. That eliminates leak issue. If you can't or won't, then have you sealed all of the joints and if using snapped piping, sealed the snap joints. I'd use an aluminum tape for this, cheap and adheres well. The fan itself usually has seal on both side plates, should not leak. Intake air is needed, I'd bring that in on opposing wall as far from exit as you can. Fan should be plenty strong enough

Keith Downing
01-06-2018, 1:44 PM
Seems like you've checked all the obvious pitfalls, and nothing stands out as a potential problem. Maybe several little things are adding up to create a problem, but I don't see any one thing from what you're describing.

I have a hard time believing that the fumes would be coming back through properly installed drywall, I was more thinking that maybe the exhaust flowed down the wall towards a vent or window you used. EDIT: As John mentioned, a separate clean air intake on the other side of the shop will probably help a LOT if that is a possibility.

And tight corners in the exhaust can impede air flow, but 45 degrees done properly shouldn't be a problem.

That blower is commonly used with decently sized lasers from what I gather around here, and I've seen few complaints. But I do have the 6" blower that's a size larger so that might make a difference. IDK how much though, or if it's worth the additional cost.

One last thing to check: if you're lasering something that gives off a reasonably noticeable odor, and you check your exhaust point outside, are you getting plenty of flow and a strong odor outside (much stronger than inside the shop)? If not, I'd say that you have something restricting the flow of your exhaust; either in the machine or along the way to the blower. If so, then you may be able to fine tune things to be more palatable, but you're probably doing most of what you can with that size blower and 4" hose.

Jacob John
01-06-2018, 2:47 PM
Thanks John and Keith, it looks like I'll be going back to each seam and resealing them just to try and narrow it down. Keith, I've gone outside, especially when we're engraving wood, and there's no doubt it's being pulled outside (heavy smoke). There's no visible smoke inside the garage, just the smell. Now I know some of that smell is coming from the wood itself once it's removed, same as the acrylic, but I worry that it's too much. I might have my industrial hygiene buddy come and run the meter too. It's really the acrylic and metal engraving I worry about. The Chromium and Nickel fuming is a pretty bad thing from a health standpoint.

John's suggestion is a good one for running a separate clean air intake. And yes that fan should be good, it sounds like a damn freight train. I really need to invest in a similar CFM, lower decibel unit.

Re Wood
01-06-2018, 4:25 PM
The Harbor Freight blowers are cheaply made, chinesium. They are not sealed. Trotec recommends Penn State Industries blowers.

I guess you could get a welder and try to seal it up yourself.

John C Cox
01-06-2018, 4:44 PM
Can you post a few pix and a sketch of your setup... Include distances if you can.

A few pitfalls...

1. Fan output on these units is rated for the fan alone - no inlet/exhaust ducting and no filter bag... If you have a copy of the fan curve - you can see how it drops off at various inches of water column (back pressure). Typical commercial and industrial fans are rated at 1/2" Water column back pressure. Often HF fans are pretty horrible - they drop off really fast as the system gets any restriction - like say the ducting and bag and safety grating over the fan inlet and exit to prevent fingers... Yes - this stuff comes from the factory.... But they don't include it in the ratings...

2. Ducting. Flex duct is horrible for back pressure/friction losses. A 10 ft run of flex can cut your CFM in half... And that doesn't count the losses from the filter bag...

3. Are you trying to vent the whole space or pick up the fumes from your machine? These things work WAY better pulling the fumes directly off the machine as close to the point of generation as possible. It takes a huge amount of ventilation if you are trying to vent "The Room"....

4. Outside air source? Whatever blows out has to be replaced with something. This has already been mentioned - but it's critical to have a source for fresh air to come into the area. And it's critical that this source is far away from the discharge so it isn't sucked right back in.... For example - open a window on the opposite wall?

John C Cox
01-06-2018, 4:51 PM
The next thing to think about is how long it takes to get an "air change" for your space - and how long you are running your fan...

Say you measure an actual 200 cfm in your duct (filter bag, ducting, and everything else)...
A hypothetical 20'x20'x10' garage is 4,000 cubic feet...
That means 1 air change = 20 minutes.... Or 3 air changes/hour... You are going to smell a LOT of fumes!!

That's honestly ineffective if you are trying to ventilate the whole space.

If you put that same duct onto an enclosure covering your machine - say 6'x6'x6'.. That's 216 cubic feet - or about 1 minute to vent the whole thing... You will be much happier....

Kev Williams
01-06-2018, 7:04 PM
I have several of the 'green' (or gray) HF blowers. They'll draw all the smoke you could ask for. The problem with smoke extraction isn't the blower or ducting.

The problem? IMO it's the machine the blower and ductwork are connected to.

I have no idea how a Trotec is set up.

My Triumph, exhaust is just a big hole in the lower back wall beneath the work table. Most of the smoke is above the table, just drifting around until it finds some air moving toward the big hole...

My GCC, it set up very similar to my LS900, it uses a plenum with a long narrow 'air slot' at 'focus level'- should work great, but some clown in Taiwan thought it would be a good idea to put a diverter plate in front of the 4" exhaust hole, which totally messes up the airflow's 'focus'...

My old ULS has a great setup, which is almost identical to my LS900, which is even better...

I just now shot this video. You'll see that I'm running a plain old HF green blower and some of the worst ducting you'll ever find.
But watch how the smoke moves-- all because Gravograph made sure it would :)


https://youtu.be/5PO7EToUDsw

As to the fumes problem, THE BLOWER MUST BE OUTSIDE, simply because they DO move a lot of air, and the ducting between the blower and the outdoors WILL be under pressure, pushing smoke into the room...

And FWIW, 3 of my 4 HF blowers are over 12 years old... :)

John Lifer
01-06-2018, 7:05 PM
Wood, the Penn state fans, along with almost 100% of everything they sell is Chinese made. Fans are identical to the HF and at least my fan has foam sealant on both side plates. I very well doubt it is the fan. I would bet a lot of the odor is burnt adhering to the laser. And there isn't much you can do about that. Especially if you are smelling after shutdown

Matt McCoy
01-06-2018, 9:02 PM
Wood, the Penn state fans, along with almost 100% of everything they sell is Chinese made. Fans are identical to the HF and at least my fan has foam sealant on both side plates. I very well doubt it is the fan. I would bet a lot of the odor is burnt adhering to the laser. And there isn't much you can do about that. Especially if you are smelling after shutdown

Kinda -- PSI dust collectors, and maybe more, are manufactured in Taiwan in a ISO9001 facility. They're well made.

Dave Sheldrake
01-06-2018, 10:23 PM
Kinda -- PSI dust collectors, and maybe more, are manufactured in Taiwan in a ISO9001 facility. They're well made.

ISO 9001 is meaningless Matt, it just means you are conforming to your own set of procedures :) I have it and it's nice on paper but worthless :)


I just now shot this video.

Ok, now I know I'm tired, the first thing that came to mind was "Wow , Kev has an American accent".......doh!

Glen Monaghan
01-06-2018, 10:26 PM
It is often best to have the blower outside (in a weather-protection housing) so all interior extraction parts will be on the blower's inlet side and therefore will have negative internal pressure. That way, any leaks in the exhaust system won't push fumes directly back into the room. It also reduces noise in the room! You might also want to either extend the exhaust out of the blower away from the building more, or raise it up higher, to help disperse odors away from the building and lessen chance of re-infiltration. Then allow for makeup air into the building as far as possible from the exhaust. When a laser job finishes, leave the lid closed with exhaust fan running long enough to ensure at least a complete turnover of air in the machine. Close the machine back up as soon as possible after removing the workpiece(s) because some residual smells can still come from the inside area that was exposed to the smoke/gasses while lasering. Likewise, things like wood and acrylic that you have lasered will continue to give off odor for some time so, if possible, don't leave them lying around in the open...

Gary Hair
01-06-2018, 11:26 PM
The green HF fans are fine, that's not your problem. I have used them for years and with three machines on one fan! The problem is likely where you have the blower - inside or outside? If it's inside then that is your problem. With the fan outside then leaks don't really matter because they are merely allowing shop air into the ducting that is being drawn out of your laser. When you push air through the ducting then every leak will expel the nasty stuff you are trying to get rid of. No amount of sealing will eliminate every leak, putting the fan outside takes that problem away. Yes, turns will decrease airflow efficiency as well as long runs. However, I had a 90 from my laser to a vertical run (about 10') then another 90 to a "T" that connected to my fibers, then 6' to the blower. All that connected to my Speedy 400 - it worked fine!!! If you want the best efficiency then exit straight out the back of your laser, through a wall, to the blower - that setup will bend the acrylic lid and draw out every bit of smoke. Don't fret the details, get your blower outside!

Jacob John
01-07-2018, 12:40 AM
Sounds like I need my blower outside. My neighbors don't care about it right now, but I wonder if that blower will be too loud. I have a tree filled neighborhood so there's some natural noise elimination because of that, but I'm not sure it's enough. Any suggestions to building that outside?

I had a crazy out the box idea. I have this guy that sits around doing nothing --> https://www.harborfreight.com/8-inch-portable-ventilator-97762.html and a closed hole that used to be an AC vent hole. I added a wall AC so this hole is just closed up (4" hole). Could I theoretically reduce 8" to 4" and use that as a supplemental vent with bendable duct? :eek::D This thing is nasty and circulates air like you wouldn't believe. It's rated at 1590 CFM, and I've run 20 feet of duct and the thing doesn't even hiccup. How stupid is this? ;)

Doug Fisher
01-07-2018, 3:04 AM
You can buy mufflers to help with the noise exiting the end. Check Amazon.

Like John said, you are going to get stuff deposited inside your laser and then the ductwork too. That will smell for days. If it is something like extruded acrylic, it will smell for long while.

Another thing to check is back draft from the outside through the ducting back through the laser's cabinet and into the room when the laser is off. That combined with the left over residue will smell up a room for quite some time. Installing a "blast gate" can minimize the backdraft.

Gary Hair
01-07-2018, 7:30 AM
Sounds like I need my blower outside. My neighbors don't care about it right now, but I wonder if that blower will be too loud. I have a tree filled neighborhood so there's some natural noise elimination because of that, but I'm not sure it's enough. Any suggestions to building that outside?

I had a crazy out the box idea. I have this guy that sits around doing nothing --> https://www.harborfreight.com/8-inch-portable-ventilator-97762.html and a closed hole that used to be an AC vent hole. I added a wall AC so this hole is just closed up (4" hole). Could I theoretically reduce 8" to 4" and use that as a supplemental vent with bendable duct? :eek::D This thing is nasty and circulates air like you wouldn't believe. It's rated at 1590 CFM, and I've run 20 feet of duct and the thing doesn't even hiccup. How stupid is this? ;)

Typically those type of fans are made to move large volumes of air but don't have much power behind them when you restrict them. Think of a box fan - tons of air but if you restricted it down a bit you lose most of your airflow. It may help, but it won't be very efficient.

Bill George
01-07-2018, 9:08 AM
Any type of propeller fan does not do well with restriction. Having worked in and around commercial HVAC/R work for 30 years or so, Yes you can seal pressure side ductwork so it has No leaks. Do a search for Hardcast.

Gary Hair
01-07-2018, 10:02 AM
Any type of propeller fan does not do well with restriction. Having worked in and around commercial HVAC/R work for 30 years or so, Yes you can seal pressure side ductwork so it has No leaks. Do a search for Hardcast.

I don't have any experience in HVAC but I'm sure you are right that ductwork can be sealed, the blower, at least the HF blower, is another story. How much time and $ would it take to seal the ductwork and the blower to a point where it doesn't leak at all? Would it not be easier, quicker, and cheaper, to just put the blower outside and be done with it? I used 4 - 2x6's to build a stand, and a rubbermaid tub to cover mine and it stayed nice and dry even in the PacNW weather. It could have leaked like a sieve but I wouldn't know it nor would I care.

Bill George
01-07-2018, 10:27 AM
Oh I don't know an hour or two putting screws in the SM joints and sealing with the proper Hardcast material for the job and all the work is inside. Beats building a dog house outside with a cover and stand, cutting a 6 inch or larger hole, running up to Code wiring and switch, and here in Iowa it was a balmy -7F last week outside.

Now if your doing a large commercial job with lots of exhaust ducts, put all your fans on the roof out of the way and keep the duct at negative pressure.

The same material for the ducts can be used to seal the fan housing. Once that stuff is on correctly, nothing gets by it. Goes on with a paint brush and special tape.

Jacob John
01-07-2018, 11:38 AM
The fan I posted was designed for ventilating a room and would not be restricted at all. I would direct line it outside. Its bigger issue is it's LOUD. :D

That's why the advice for placing it outside is under consideration right now.

Kev Williams
01-07-2018, 1:43 PM
My solution for the outdoor blower problem:

I bought a plastic patio bench/storage box from HD about 3 years ago, cheapest one I could find, about $50-

Now don't laugh, this is a work in progress, but it works great! - My problem is finding time to finish the job ;) - I just did this last summer...
375718375719375720
The duct comes down from the garage window, into the back side of the box thru a 4" hole, connects to the blower, exits out the left side then enters my experimental 'smell' box, which is semi-filled with cheap charcoal briquettes, then exits the other side of the box. The charcoal helps a lot, but I need more of it. The box, which I though would resonate and make the blower more noisy, does just the opposite, it cut the noise by half. The exit air makes no noise. I have the blower sitting on some pink insulation which I assume helps. At 1am, standing 25' away you can barely hear it. From 50' away it's near dead silent. Neighbors say they can't hear it :) I ran it all summer, no heat issues, the motor gets the air it needs from the hole in the side of the box, and the box is anything but airtight so warm air just gets pushed out.

The other blower sitting there is also going inside the box, as there's plenty of room for both of them. That's why all the excess ductwork, it'll get trimmed up when I get the other blower put in the box...

Keith Downing
01-07-2018, 1:53 PM
I've always wondered: is there any issue with putting an insulated box around the blower? Do they need room to displace heat or any airflow for the motor?

Dee Gallo
01-07-2018, 3:47 PM
I have had an insulated box around mine for years and it has never had a problem. Originally it was just a square box made out of blue board built around a rubbermaid box for critter proofing, but later I added an A-frame to shed snow. I installed a flap dryer vent to allow the flow out. There are blast gates inside the house.

kyle bonnell
01-13-2018, 9:38 PM
Are you sure the smell isn't coming from the exhaust getting reformulated back up through the eaves of your garage?

Jason Alan
01-30-2018, 11:52 PM
My solution for the outdoor blower problem:

I bought a plastic patio bench/storage box from HD about 3 years ago, cheapest one I could find, about $50-

Now don't laugh, this is a work in progress, but it works great! - My problem is finding time to finish the job ;) - I just did this last summer...
375718375719375720
The duct comes down from the garage window, into the back side of the box thru a 4" hole, connects to the blower, exits out the left side then enters my experimental 'smell' box, which is semi-filled with cheap charcoal briquettes, then exits the other side of the box. The charcoal helps a lot, but I need more of it. The box, which I though would resonate and make the blower more noisy, does just the opposite, it cut the noise by half. The exit air makes no noise. I have the blower sitting on some pink insulation which I assume helps. At 1am, standing 25' away you can barely hear it. From 50' away it's near dead silent. Neighbors say they can't hear it :) I ran it all summer, no heat issues, the motor gets the air it needs from the hole in the side of the box, and the box is anything but airtight so warm air just gets pushed out.

The other blower sitting there is also going inside the box, as there's plenty of room for both of them. That's why all the excess ductwork, it'll get trimmed up when I get the other blower put in the box...

How about rain resistance? Is the box pretty waterproof? I live in WA and we get a lot of rain.

Tim Bateson
01-31-2018, 9:08 AM
I eliminated the smoke/fume issue by throwing away the flexible metal piping that I tried in vain to seal. I moved to the green sewer PVC piping. Not only did I get rid of smoke and fumes, but the draw has greatly improved.

Jason Alan
01-31-2018, 9:40 AM
Does white pvc pipe not work?

Kev Williams
01-31-2018, 12:07 PM
How about rain resistance? Is the box pretty waterproof? I live in WA and we get a lot of rain.
Yes, the box is a 'patio bench/storage box' and no water seems to get in. It has drain holes so if any water does get in it'll get out too. The box on top is just a basic storage box. So far it's all survived a full year outside, the blower seems unaffected running all day inside the box in 100° heat (the box is on the north side of the garage so it's mostly shaded all day), and we had a foot of snow last week, the excess hose didn't suffer, the box tops got wet but that's about it. I'm HOPING to finish the setup this weekend, with 2 blowers in the box all piped decently :)

Misty Smith
01-17-2019, 11:37 PM
So in theory Blower 1 pulls air from the laser and pushes it into the charcoal pit. Blower 2 pulls the air from the charcoal pit and pushes the air outside?? How many lbs of briquettes are you using?

Misty Smith
01-18-2019, 12:09 AM
I'm having a similar issue
Did you find a solution?