Getting a lot of fumes, need some troubleshooting advice.

[Glen Monaghan]

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]

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]

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...tor-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? 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]

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]

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...tor-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? 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]

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]

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]

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]

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.

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

[Kev Williams]

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...
odb1.jpgodb2.jpgodb3.jpg
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]

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]

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]

Are you sure the smell isn't coming from the exhaust getting reformulated back up through the eaves of your garage?

[Jason Alan]

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...
odb1.jpgodb2.jpgodb3.jpg
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]

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.