Fan fire hazard

[Acuratechva]

I've been researching of different options for a home paint booth exhaust fan.

One of the things i have seen people say is having a brushed fan motor is a fire hazard. (I've yet to see a brushless duct or any other type fan so i guess that's implied)

Anyone agree with that? It kind of seems logical but these paint gasoline fumes were talking about...i mean, what kind of concentration of paint fumes would have to be present in order for it to ignite?

It seems like everyone i see uses regular fans when painting. Yet to hear a horror story.

 

[A_Pmech]

Most box fans are induction motors, as are most blower motors.

While the "correct" way to handle the problem is a fan designed specifically for the application, I've seen small grain dryer fans with a TEFC motors and a remote switches used in body shops.

An "explosion proof" motor isolates not only the motor and windings, but also the motor terminal connection space from the hazardous environment. Sparks originate from more than just brushes.

 

[joe_padavano]

Can't you just put the fan on the upstream side of the booth, in a "pusher" configuration instead of a "puller"?

 

[Acuratechva]

Can't you just put the fan on the upstream side of the booth, in a "pusher" configuration instead of a "puller"?

Pushing air in will just create turbulence. Idea is to **** the dry spray out so you can see and keep it off the parts.


Ultimately id like to use something like this

http://www.homedepot.com/p/Bodor-ve...-Mixed-Flow-In-Line-Duct-Fan-TT-200/204629635

Calls for " benefits of axial and centrifugal fans" does that imply its safe-ER?

 

[Falcon67]

If you are venting explosive fumes like paint or fuel, then you'd need a fan with an explosion proof motor housing.

>It seems like everyone i see uses regular fans when painting. Yet to hear a horror story.
Because most people smart but on the cheap recognize the fire hazard and use fans in a pusher configuration. I've used filtered box fans, but they were blowing into the space. At the very least you'd need a TEFC motor. You might get away without, but that one time would be a doozy.

473 CFM ain't much for a paint booth.

 

[LS6 Tommy]

Dust is an issue, too. Most airborne fine particles can be an explosion hazard. In the "real world" all spraybooth or dusty atmophere exhaust fans are required to be explosion proof...

Tommy

 

[Acuratechva]

Dust is an issue, too. Most airborne fine particles can be an explosion hazard. In the "real world" all spraybooth or dusty atmophere exhaust fans are required to be explosion proof...

Tommy

Well dust and dry spray is the easy part, i wanted to put a register with an air filter, it should get most if not all the flying ****.

 

[Jlbc212]

I can't remember a fire I responded to caused by a fan with spray paint or dust, but I've seen plenty of flash explosion/fires caused by other ignition sources. When such a flash explosion/fire does occur occupants in the affected space most often suffer serious burns, external (hair & skin) and internal (airways & lungs). Large spray painting projects should be performed in a properly designed and vented spray booth. Smaller projects should be performed in a well ventilated area that does not have any potential ignition source nearby.

 

[LS6 Tommy]

Well dust and dry spray is the easy part, i wanted to put a register with an air filter, it should get most if not all the flying ****.

True spray trap filters require pretty good flow rates. If you go that crazy, you're going to need a relatively serious fan setup.

Don't get me wrong. I'm going to put a gable vent fan in my garage eventually. I'm not saying the only way to go is a full blown spray booth setup. I'm just putting up what I know.

Tommy

 

[Cyberbear]

In older spray booth units, as well as dust removal systems, I've seen the blade or fan being powered by an outside the ducting motor and fan belt system. This takes the motor away from any concentrated fumes altogether, thus reducing a conflagration. This consists of a simple fan and pulley, driven by a remote motor and pulley. Pretty simple and does not require any expensive explosion proof components.

 

[Acuratechva]

Well, i am thinking ventilation is always good in the shop even if i dont use it just for paint. Huffing break cleaner isnt always a feel good trip lol. So if i have to invest 700 in it, i may as well have it be paint compliant and paranoia free.



This here is nice http://www.northerntool.com/shop/tools/product_200461050_200461050

Tell me if i am thinking righ. In order for it to pull air up it would have to be mounted with that big *** motor facing the floor right? (i knwo stupid question but i want to make sure i dont over look anything)

If so i'd have to mount it up in the attic since this motor hangs down, and then make piping up to vent obove the roof. So basically make a box enclosure above the joist and create a trap door (or just a large 12x12" home ac type register with those cheap month filters, they are pretty flow friendly)

Half the problem is that a lot of bigger 12+" fans are 230 volt, i just closed up my wall when i ran compressor wiring. Didn't think fan would need that much voltage so going back in is a major hassle. Also, most are 24" which is way too big to build and enclosure for which is why i was thinking an inline duct at first.


By looking at the fan above biggest pain would be making the conversion from square box to 12" duct and connecting it to an average Attic Fan shroud such as this one.

Ideas? Coments?

 

[dawgee]

why not mount the motor else where and use a pulley and belt system with the blade on a set of bearings?

 

[SeattleKent]

I went through the same debate and ended up getting an explosion proof fan.

Using normal fans would require pushing air, not very effective, or pulling and running the risk of an explosion. It is a small risk but really, really bad.

I got a Jenny Fan. Model D1633XV-A16 cost $600 from Summit Racing. I built a wood tube and mounted the fan inside. Picked up a couple of filters at the local auto paint store and mounted in front of the fan. Put one end of the tube in my PVC pipe spray booth and the other end by the garage door. Open the door a couple of feet. Turn the fan on. No more paint fumes.

 

[Acuratechva]

why not mount the motor else where and use a pulley and belt system with the blade on a set of bearings?

Just sounds like a big pain in the *** honestly. If you can recommend a ready to go fan with no ghetto rigging id appreciate it.

I went through the same debate and ended up getting an explosion proof fan.

Using normal fans would require pushing air, not very effective, or pulling and running the risk of an explosion. It is a small risk but really, really bad.

I got a Jenny Fan. Model D1633XV-A16 cost $600 from Summit Racing. I built a wood tube and mounted the fan inside. Picked up a couple of filters at the local auto paint store and mounted in front of the fan. Put one end of the tube in my PVC pipe spray booth and the other end by the garage door. Open the door a couple of feet. Turn the fan on. No more paint fumes.

Yeah my point exactly. Its not a horrible investment and best to just do it right.

I am looking to make this an attic-vent to above roof deal to keep neighbors from acting up plus once set up ceiling fan is there, just lfip a switch. No need to set up.

How would you personaly compare it to the one at Northern i linked to? They are both explosion proof.

 

[SeattleKent]

How would you personaly compare it to the one at Northern i linked to? They are both explosion proof.

The Northern Tool one is 12 which moves 1,640 CFM. The Jenny fan is 16" and moves 2,810 CFM. The Jenny fan is also variable speed.

How large is the room? Figure the room volume and divide by CFM and see how often the air changes. There is some magic number you want to achieve, something like 2 or 3 changes of air per minute. I don't remember the exact number.

Looks like the Jenny fan went up in price to $740.

If you are using to exhausting paint spray, you'll want to put some sort of filter over the fan.

 

[Acuratechva]

The Northern Tool one is 12 which moves 1,640 CFM. The Jenny fan is 16" and moves 2,810 CFM. The Jenny fan is also variable speed.

How large is the room? Figure the room volume and divide by CFM and see how often the air changes. There is some magic number you want to achieve, something like 2 or 3 changes of air per minute. I don't remember the exact number.

Looks like the Jenny fan went up in price to $740.

If you are using to exhausting paint spray, you'll want to put some sort of filter over the fan.

Oh its a small 250sqft. But i like Norther one better because its easyer to make an enclosure for you. quick 2x4 frame and bolt it right up without worrying about gaps and such.


Think its going to be enough flow?

 

[SeattleKent]

Oh its a small 250sqft. But i like Norther one better because its easyer to make an enclosure for you. quick 2x4 frame and bolt it right up without worrying about gaps and such.


Think its going to be enough flow?

If you are doing the whole garage then neither fan will really be enough. Say the ceiling is 9 feet high, then the volume is 2,225 cubic feet. The Northern Tools fan will change the air every minute and a half assuming everything is perfect. Probably not perfect so it is more like every three or four minutes. Is sucking 1,600 CFM enough to create a cross flow breeze?

For comparison, my spray booth is 8' x 10' and 8' high -- 640 cubic feet. When I turn the fan on, even half speed, I feel a breeze across the booth. The over spray is quickly sucked towards the fan.

Maybe install the fan as a standard exhaust fan and put up some plastic sheeting around it for when spraying.

 

[Acuratechva]

Yeah i just looked it up and it says 100fpm is optimal. Which means i need something like 25000 cfm fan lol.

Since i got you here how many air exchanges per minute are recommended? thats one thing i was not able to find solid info . most just refer to FPM instead of number of air changes.

 

[SeattleKent]

I could not find the number either. Something like 2.5 or 3 per minute is very good.

I probably run lower than that. I set the fan to a middle speed then start spraying. If I see clouds of paint I turn up the fan until the air is clear while spraying.

Good luck!

 

[Gerald O]

Lots of folks talk about "pushing" air into a paint booth as being bad, and "pulling" air out as good, but most of this is hearsay horseshit by people with no experience with doing it both ways. The fact is that what goes out must come in. Turbulence in the air is mostly a factor of inlet and outlet vent shape, size, and position rather than whether there is a east to west or west to east pressure gradient.

In a DIY spray booth in your garage you're not going to have a scientifically designed airflow system with laminar flow paths and pressure gradients. "Turbulence" in the air is going to be the least of your problems and is way overrated. Dirt in your paint, clear air to see, and fresh air to breath are going to be your biggest problems. My preference for a DIY booth is to have it under positive inside pressure so that dirt doesn't get sucked in through all those leaks you are guaranteed to have. This means you blow in, not **** out.

If you blow in the fresh air through a filter, and you must, then that is going to diffuse the airflow coming in so that there is no fan induced turbulence. As long as the inlet air isn't blowing directly and closely at your work you'll be fine.

 

[JCQuick]

Most good paint booths have explosion proof fan motors as well as lights meaning the lights are housed behind sealed glass. I use to sell paint booths

that being said I have seen many a home made booth with regular fans and nothing happen. But it could

 

[SeattleKent]

These discussion got me curious. Could I actually find any examples of spray booth fires?

In internet search quickly turned up this explosion from 2010:


From: MTDG at yahoogroups.com
On Behalf Of Anthony Oteri
Sent: Thursday, February 18, 2010 6:07 PM
To: MTDG
Subject: Spray booth story, sad story

I know this topic has come up in the past but it needs to be discussed again. I friend of mine built his own spray paint booth from a kitchen stove exhaust hood that he was using in his garage. Last night he was using it when it caught on fire. He has burns on his chest, arms, face and head. His wife told me he has no eyebrows, eye lashes or hair left on his head. He also wears contact lenses which melted in his eyes from the fire. He's in pretty bad shape and was transferred to a Shriners burns hospital in Boston. He was using Testors rattle can enamel on an airplane model that he was building. His wife told me she herd a boom sound then a scream. When she opened the door into the garage his shirt was on fire. Luckily there daughter's boy friend was there and he used a fire extinguisher on him to put out the fire. If anyone is using a home made spray booth don't use it anymore. The fan motor windings are exposed and will ignite paint fumes and vapors. You need to use a motor this is in a vapor proof or explosion proof case. This guy Dennis is 47 years old and is a pipe fitter by trade, ironically he installs fire sprinklers. I didn't intend to ruin anyone's dinner, but I hope it may help save yourself from getting hurt, or worse. Sorry for the gloom and doom, be careful!
Anthony

One explosion five years ago does not sound that bad. Then I dug a little deeper:

Fire in Easton High School spray booth

Faulty Spray Booth Sparks Blaze

New Jersey fire in auto repair spray booth

Fire in Syracuse Paint Booth

Fire at Western Star Trucks in Portland

Andy's Auto rebuilt after fire in paint booth


Anyway, enough said.

I was surprised at the number. Maybe the truism that these never happen may not be so true.

 

[JCQuick]

^^^ yep not surprised at all

 

[PCMusicGuy]

Does anyone make much smaller scale explosion proof fans, say like 6" in diameter? Can any of them run on DC voltage?

 

[Jlbc212]

Just about every fire regulation, such as the requirement for explosion proof fans and lights in spray booths, has been put in place because of a disaster that occurred somewhere.

 

[dave89iroc]

Does anyone make much smaller scale explosion proof fans, say like 6" in diameter? Can any of them run on DC voltage?

continuous duty bilge blower

 

[Acuratechva]

Well this has been productive and frightening haha

 

[kbs2244]

If you are a DIY type...
Any clothes dryer will have a blower with the motor mounted out side the air flow.
They do not want the lint to catch fire.
They move a pretty good volume of air, and come with a 4 inch duct.

 

[LS6 Tommy]

If you are a DIY type...
Any clothes dryer will have a blower with the motor mounted out side the air flow.
They do not want the lint to catch fire.
They move a pretty good volume of air, and come with a 4 inch duct.

The motor is not in the air flow through the duct. Depending on installaion, it may still be in the space where the spraying is being done...

Tommy

 

[DMaxRocks]

Lots of folks talk about "pushing" air into a paint booth as being bad, and "pulling" air out as good, but most of this is hearsay horseshit by people with no experience with doing it both ways. The fact is that what goes out must come in. Turbulence in the air is mostly a factor of inlet and outlet vent shape, size, and position rather than whether there is a east to west or west to east pressure gradient.

In a DIY spray booth in your garage you're not going to have a scientifically designed airflow system with laminar flow paths and pressure gradients. "Turbulence" in the air is going to be the least of your problems and is way overrated. Dirt in your paint, clear air to see, and fresh air to breath are going to be your biggest problems. My preference for a DIY booth is to have it under positive inside pressure so that dirt doesn't get sucked in through all those leaks you are guaranteed to have. This means you blow in, not **** out.

If you blow in the fresh air through a filter, and you must, then that is going to diffuse the airflow coming in so that there is no fan induced turbulence. As long as the inlet air isn't blowing directly and closely at your work you'll be fine.

Gerald, thank you for your post, this has been my thinking as well. If you are putting *** CFM air into the booth, that same amount has to be leaving the booth...albeit it may be through leaks in the walls which is far better than pulling dirty outside air into the booth. I thought a couple of fans with the correct CFM that have filters installed in front of them, mounted on one side of the booth, and a row of filters on the other side of the booth, should work about as well as anything in a homemade paint booth. This solution takes the exploding fan totally out of the equation.

-Mark