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Thread: spray room filter and fan .

  1. #1
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    spray room filter and fan .

    i have finish room thats 5.5' by 12' that want to upgrade my homemade exast filter and fan to something more effecent. basically when done spraying a cabinet the room is full of overspray. loking to buy a fan and filter assembly that will keep up with overspray. i use hvlp gun. been dealing with for 15 years....

  2. #2
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    You need an explosion proof fan, and as I found out when building a spray room, they are not cheap. As for sizing, the standard has been 100 LINEAR feet per minute. If your ceiling is 8’ then that would be for you 5.5 x 8 x 100, so you would need a 4,400 CFM fan to achieve 100 linear feet per minute.

    OSHA has, from my research, updated its requirement for spraying liquids to 4 air exchanges per minute, ie enough cfm to replace the air in the spray booth four times every minute. That would mean, with an 8’ ceiling, that you have 5.5 x 8 x 12 = 528 CuFt x 4 cycles per minute = 2112 CFM fan needed to meet that requirement.

    The 100 linear feet per minute standard is what I had always been told was the gold standard in automotive spray booths. That is based on an empty room, but it gets complicated when you factor in a vehicle (using the automotive example) which takes up a lot of air space. For a furniture spray booth, you probably won’t have large volume pieces in there, so probably would be best to go with the higher estimate.

    I used a belt driven exhaust fan and swapped the motor for an explosion proof one I found on eBay. I made my spray booth too big and needed a huge fan. Lesson learned!

  3. #3
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    Do you still need an explosion proof [fan] motor if, like a lot of people, you hang up shower curtains from the overhead, or a PVC frame, forming maybe an 8x8 square and use a box fan or two?

  4. #4
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    I took the approach of installing an explosion proof fan, and couldn't be happier. One thing to keep in mind, is that you absolutely need makeup air with that setup. When mine is on, it literally rapidly swings the shop door open with serious force if you forget to open it.

    I initially had automated louvers installed outside the house on the fan housing. After they failed (they were installed backwards) my electrician suggested that the force of the fan would easily open them, and the spring close them without the electricity. He was totally right about that. Don't waste your money on those.

    I just think the ability to use lacquer is a huge bonus, as it the ability to worry far less about the dangers of volatile finishes. For me it was money well spent.
    - Its not that Im so smart, its just that I stay with problems longer. Albert Einstein
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  5. #5
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    An explosion proof fan is required if one is spraying materials that are, um...explosive. It's not "required" for waterborne finishes and I'd not be concerned with shellac, either. Using one isn't a horrible idea, however, and does present the flexibility should one need/want to spray something a bit more dangerous for a specific project, such as NC lacquer for a guitar project. For that, the venting has to go outside.

    Relevant to the OP's question, as long as the finishes being sprayed are waterborne, a capable fan combined with typical rectangular filters can be used to vent the space and clear the particulates from the air. And with waterborne finishes, the venting does not have to exit the building...the filtered air can just return to where it came from.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  6. #6
    I would be cautious about non-vented systems for waterborne finishes. The fumes are not flammable, but they are not necessarily non-toxic.

  7. #7
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    So, curious question. How dangerous are the fumes from spraying stuff like oil based polyurethane and lacquer when sprayed through a low volume HVLP? Is an open garage door enough ventilation? Would these fumes be really flammable? I'm not looking to create a shower curtain enclosure (that would keep the fumes closed in and dense).

  8. #8
    Quote Originally Posted by Aaron Inami View Post
    So, curious question. How dangerous are the fumes from spraying stuff like oil based polyurethane and lacquer when sprayed through a low volume HVLP? Is an open garage door enough ventilation? Would these fumes be really flammable? I'm not looking to create a shower curtain enclosure (that would keep the fumes closed in and dense).
    Depends on the solvents involved. They definitely are flammable. None of them are good for you. Positive airflow, filtration and exhaust keep overspray from settling on the work and surrounding equipment and escaping into the environment, prevent the buildup of an explosive gas concentration and reduce personal exposure to whatever is evaporating from the product.

  9. #9
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    I am currently using an Iwata LPH300 HVLP gun. This actually has a very small output and is very controllable with almost no overspray. I may end up changing to an LPH400 as this LPH300 seems to dry out the finish too fast as it is coming out of the gun. I always use a 3M P100 respirator. I'm really just concerned about fumes being explosive, but I generally have an open garage door when I am spraying.

  10. #10
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    Quote Originally Posted by Aaron Inami View Post
    I am currently using an Iwata LPH300 HVLP gun. This actually has a very small output and is very controllable with almost no overspray. I may end up changing to an LPH400 as this LPH300 seems to dry out the finish too fast as it is coming out of the gun. I always use a 3M P100 respirator. I'm really just concerned about fumes being explosive, but I generally have an open garage door when I am spraying.
    Aside form the "explosion" question methinks you should be using the 3M cartridges with the carbon filtering (#6001) that are meant for solvents ("organic vapours")
    I have two separate 3M half masks, one with the pink P100 (round) filters and one with the 6001 charcoal filters (kind of oblong shaped)
    3M does make a combo filter that has both the P100 material and the 6001 material in one cartridge. If that is what you are using on your respirator then you are fine.

    I read somewhere that a "quick and dirty" test of your respirator is : If you can smell the material your working with (e.g., wood, paint, metal) you are inhaling the associated particulates.
    Granted some really nasty stuff is odorless, but "the smell test" is generally a good starting point.
    Last edited by Patty Hann; 02-04-2023 at 9:38 PM.

  11. #11
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    One critical area that many overlook when attempting to ventilate a space. To move air out of a space, you have to let an equal amount of air in. Even an open garage door doesn't provide adequate ventilation if you are back away from the doorway. I've seen many instances in homes and commercial buildings where people place fans that are moving air, but not actually ventilating the space. A large fan placed several feet from an open window doesn't necessarily blow any fumes out the window, even if there is another open window somewhere in the room. Nor does a fan in a window necessarily draw air from one particular location in a room that is not on the path of least resistance to air flow.

    I was recently in our local shopping mall. One of the large clothing stores had experienced a significant water leak in their ceiling. This leak soaked the carpet on the floor, lots of clothing and display racks. They had dozens of fans running, pointing in different directions attempting to dry things. The humidity in the area was extremely high, but there was no venting of the air to the outside nor new dry air coming in.
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  12. #12
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    Patty - thanks. I have never "smelled" any sort of odor or scent when I am spraying with the P100 masks, but I'll switchover to the 6001's for sure.

  13. #13
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    the amish guy buy finish from has wood stove heating his spray area. has far run by belt sucking finish out though. ... was not in that area of his shop long...

  14. #14
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    Quote Originally Posted by Alan Lightstone View Post
    ... you absolutely need makeup air with that setup. ...
    That's FILTERED makeup air.

  15. #15
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    Quote Originally Posted by Wayne Cannon View Post
    That's FILTERED makeup air.
    I do this with a box filter in the window in the spray room. Made a small wooden frame for it. I also run my air cleaners on high when I spray. Seems to work just fine.
    - Its not that Im so smart, its just that I stay with problems longer. Albert Einstein
    - Welcome to Florida. Where the old folks visit their parents

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