# Paint Fume Extraction



## cstrang (Sep 22, 2009)

Hey guys, and gals. I am going to be preparing my finishing room for spraying finishes, I am going to make a filter box with ducting going to the next room, and then it will attach to a blower like the one pictured below. From there it will go through more ducting and then outside. My questions are where is a good place to shop for a blower like this? Cost and quality being taken into consideration. What are some good filters to get? And do any of you have a different, what you would think better way in mind? I have considered some different options and this is the best that I could see but I could have overlooked something, there are many ways to do one task.


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## davidpettinger (Aug 21, 2009)

You may want to go to your automotive paint supply store and look into the filters they use for auto spray booths. They are specifically designed to remove particulate matter from the air. They are also designed for efficient air transfer.


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## lew (Feb 13, 2008)

Just a thought, will this be the most efficient type of air mover? Usually a squirrel cage fan will move more air to evacuate airborne particles.

Lew


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## Sawkerf (Dec 31, 2009)

How big is your paint booth, and what's the flow rating on those blowers? They don't look like they're big enough to move enough air to be very effective in a paint booth.

A 10' x 10' x 10' booth is 1000 cubic feet and you'll probably need at least 1000 cfm to be sorta effective.


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## cstrang (Sep 22, 2009)

UnionLabel and Lew, ill look into those ideas

Sawkerf, My booth is 12×8x7 so 672 cubic feet, that blower is rated for 892 cfm

Thanks guys.


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## wisno (Feb 26, 2010)

You need to find spray booth supplier.
For your reference how to make finishing room you can view my articles about finishing room in :
- Finishing room
- Spray booth for furniture finishing
- exhaust fan for furniture finishing

good luck

wisno


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## eastside (Jun 21, 2009)

PENNSTATEIND.CO iTEM #DC250SEMB or DCSUP35MB The first one looks like what you want looking at your picture.


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## Sawkerf (Dec 31, 2009)

I don't think that you have nearly enough blower capacity for your booth. If the blower inlets are 4" in diameter, the air velocity at the inlets is ~9900 fpm, or ~110 mph. That sounds pretty good, but the real issue is getting enough air velocity at the entrance (i.e. open side) of your booth to move the spray droplets into the blower. If the open side is 12'W x 8'H, your blower will only generate ~9 fpm (~0.1 mph) at the opening.

Those are rough numbers for a wide open, unobstructed, system. Adding an exhaust line will reduce that rated flow, and any filtration on the inlet side will really drop it. There will be even more loss as the filters load up.

You have a great idea, but I would suggest a visit to a paint shop to tour their setup before you spend much money on something that probably won't do the job you want.


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## cstrang (Sep 22, 2009)

I have a picture of the paint room now and some sketch-up drawings to give you guys a better idea of what i have in mind, thanks for all the input so far.




























***Both rooms are approx. 8' wide


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## Gofor (Jan 12, 2008)

Your drawing suggest you will be exhausting all the clean air coming in the lower vent and doing nothing for the fumes. You have little air flow across the room.

First, I would suggest you blow air into the room,and filter the exhaust out. This would eliminate the exhaust duct (use filter panels in the window), and move the inlet into the room over the entrance door (providing a fresh air flow across the room) if you use the proposed blower.

Second, there are two standards for paint rooms/booths. Booths are usually graded on feet per minute airflow over the object being painted. (minimum about 60 fpm and design around 100. This allows for the filters to restrict air flow as they load up). Rooms are graded on total air volume changes over a longer time period. Your design calls for volume air changes rather than feet per minute (volume changes are usually easier to achieve which is in your favor,) I think its about 12 or 15 per hour, but it has been over 10 years since I worked with OSHA specs on this.

Larger window box fans in the openings by the door will give you more volume input, eliminate the need for explosion/fume proof motors as they will have fresh air going over them, and will increase the volume with smaller hp.

If you use your design as posted, you need to eliminate the air inlets under the window.

just a thought

Go


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## cstrang (Sep 22, 2009)

Gofor, this gives me something to ponder, using box fans would be a more cost effective route, since I am only going to be in this location for another couple of years or so, cost effectiveness is an issue. My only concern about venting out the window is my neighbor's house is relatively close, if I vented out the rear like the picture shows (air coming in from main shop in the front of the booth and getting pulled out by the blower) then exhausting out the rear of the house via duct and an exterior vent. As for the inlets under the window, these are not inlets; the blower motor would be sucking air through these and out of the house. Thanks for the input.


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## Gofor (Jan 12, 2008)

My bad, I misread your design. I still think blowing air in and maybe increasing the exhaust duct size (or diverting the window exhaust sideways through an outside duct maybe using one window if you still need the light?) would be less expensive and more efficient. Don't know what the walls are made of and how hard it will be to make your exhaust hole. A larger exhaust duct behind where you have the chair on the finish bench in your picture would be the optimum position providing you can let enough air out. For most furniture spraying, you won't need to go to production booth standards. The best scenario is where you don't have to wear a respirator, but that is always an option.

Go


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## cstrang (Sep 22, 2009)

Gofor, you've got me thinking now, its almost midnight and my mind is going a mile a minute lol. I think that having a few box fans and blowing air in may be the way to go. Even if this didn't work out I wouldn't be taking much of a loss, I still need to cut the holes in the wall for the air intake and I will probably try the window exhaust first, see how bad it is and if it doesn't work out I can always duct to the rear of the house if need be. I will be wearing a respirator regardless of the air flow, I just want to channel the overspray in one main direction and exhaust the fumes to eliminate them spreading to the rest of the house. I am currently away from the shop but will be flying home on Friday evening, I think ill give this a try next week. By the way, do you know the avg. cfm of a 20" box fan?


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## Sawkerf (Dec 31, 2009)

I hope that you get along really well with those neighbors. I operate my cabinet/furniture business out of my garage shop and shortly after I started up, I got a visit from a city inspector. His only real concern was how I used and stored my stains and finishes. As it happened, I was loading some cabinets on the truck for the trip to my finish guy, and I told him that my only in-shop finshing was on small pieces using using brushes or rags and small containers of stain/finish - just like hobbyists all over the city.

He either didn't see (or ignored) my HVLP rig, and I didn't call attention to it. He gave me the standard speech about commercial finishing shops needing approved spray booths, and went on his way.

I've never thought of building a spray booth, and have only "shot" a few things in the driveway when the weather was perfect (i.e. ZERO wind). I've gotten along great with my neighbors, for over 30 years and don't want to do anything to mess that up. - lol


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## cstrang (Sep 22, 2009)

I do get along good with the neighbors, I will consult with them after I do a bit of spraying to make sure they are not botherd by the exhaust location, if they are I will have to move it.


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## roman (Sep 28, 2007)

make sure the unit is explosion proof.


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## cstrang (Sep 22, 2009)

Any exhaust fan that I use will be explosion proof, I have viewd some booths in industry and want to get mine "up to snuff" for spraying. Safety is a big factor in my shop.


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## Sawkerf (Dec 31, 2009)

Sorry, but I just don't think that your planned blower capacity (972 cfm) will be anywhere near enough. That rating is across the inlet and exhaust of the unducted blower, and your drawing shows ~ 10' - 12' of straight duct, three elbows, and filters.

Find a reference book that gives head losses for smooth walled pipe and fittings and calculate the losses you'll get with your intake and exhaust ducting. Straight sections will have head losses of X ft/ft of run, and the elbows will have "equivalent lengths" that are multiples of the straight sections. Typically, a 90* elbow will cause a loss equivalent to 3' - 5' of straight pipe. Your filters will introduce additional losses which will increase as they load up.

My finish guy had to shut down his spray booth last year for a couple of months and built a temporary booth about the size of yours using 2×4's and sheet plastic, One end was completely open, and he had ~10 sq ft of filters in the other end. He used a 36" floor fan outside the booth at the filter end to draw air thru the booth and filters. I don't know the cfm rating of the floor fan, but his temporary booth was only marginally effective. The air flow at the open end was barely noticeable and much of his over spray wound up on the floor.

His "real" booth is much larger, and has a wall of filters on each end When the fan(s) are running, there's enough air flow to make it difficult to even open the entrance doors.


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## cstrang (Sep 22, 2009)

After doing come calculations I have the same fear Sawkerf, I need a different solution to my problem. I may try the box fan idea Gofor suggested as a temporary fix until I get some more money to better my booth. When I move back to this shop during the summer I will be buying a new jointer and planer, which will without a doubt eat up some funds.


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