spray booth explosion

[Guest]

Pace Spray booth ( www.pacepaintbooths.com ) for me! I don't remember the cost (it was a gift) but I know it was under $200. (now the price is $225.) and less $$$ than MicroMark booths. Also I can buy replacement filters at any hardware store. Stainless steel is easy to clean up, but I cover the inside with Glad "Press 'n Seal".

forgot the pic! Lol.

[58 Impala]

I went looking around the Grainger website and found several shade-pole squirrel cage blowers. They had external 115v motors,100-200 cfm,and were $50-$100.I wonder if these would be sufficient and safe? I'd really like to build a booth to the dimensions I want,but I don't want to build anything dangerous. Any comments or opinions out there?

[Art Anderson]

I genuinely feel bad for the guy, and hope he makes a full recovery.

I'll continue to use my homemade booth, thanks. I hate to say it, but his choice of equipment was the cause of the accident; a kitchen exhaust fan isn't normally subjected to flammable vapors, so their exposed windings are not an issue. A brushless fan motor will help prevent such an an awful thing from happening to anyone else

Kitchen exhaust hood fans surely are exposed to flammables! Try grease fires, for example. Exposed windings of an induction (brushless motors) are almost never the issue here. What is the issue is, static electricity--which causes more exhaust system explosions and fires than sparks from electric motor brushes.

The answer here is to keep your system clean, by vacuuming it frequently. The overspray from your airbrush is very finely divided particles of a very flammable substance--dried enamel or lacquer burns readily. So, vacuuming the booth, AND the exhaust ductwork is highly advised, on a frequent basis, AND washing out the filters as well (or replacing them if they are replaceable.

I learned all I want to learn about flash fires and explosions when I was 12, back in the summer of 1956. It was one of my chores to burn trash (back then, everyone had a burn pile or burn cage out at the back of the yard for that purpose it seemed). Unbeknownst to me, Dad had tossed an empty turpentine can in the trash, cap off, and when I lit a match to start that fire, it when WHOOM! Right in my face! The flash fire ruined my eyeglass frames (plastic) even though the lenses were glass, burned away my eyebrows, and all the hair on the front half of my head, left me with first and second degree burns all over my face, neck and upper chest (no shirt to catch fire, the weather was too hot for that!). I've never forgotten the tears in my parents' eyes when they got home in response to my frantic phone call to Mom at her office, nor will I ever forget the intense pain of those burns. Fortunately, I fell back onto the ground when it happened, so I didn't inhale any of the flame, back then that would have been crippling, if not fatal. (After a month or so, it all healed up, I didn't have any scars to show off when I started the 7th grade, but the experience has stuck with me ever since.)

So, be careful, keep your spray booth and its filter clean as much as possible, OK? And, be sure to ground your motor AND the booth, if it's metal.

Art

[Aaronw]

I went looking around the Grainger website and found several shade-pole squirrel cage blowers. They had external 115v motors,100-200 cfm,and were $50-$100.I wonder if these would be sufficient and safe? I'd really like to build a booth to the dimensions I want,but I don't want to build anything dangerous. Any comments or opinions out there?

The rule of thumb is to have 100 feet per minute for a cross draft, or 50 feet per minute for a down draft booth. To find this figure take the square footage of the face (the opening) and divide into the cfm of the fan. Just to make it easy lets take a 24"x18" opening which is 3 square feet. If this was a cross draft you would need a 300 cfm fan, if it was a dwon draft you would want a 150cfm fan. You also have to factor in your ducting, if you look at the ratings you should see something like 300 cfm @ 0.000 in SP, 290 cfm @ 0.100 in SP, 275 cfm @ 0.200 in SP etc.

Cross draft = air goes out the back or side, down draft = air goes out the bottom.

To put it simply each 0.1 in SP = 10 feet of ducting (or equivelant, 1 fot of that flexible dryer ducting = about 3 feet of smooth metal duct, small diameter duct adds more than larger diameter, and turns add considerably to the effective length).

There are charts you can look up to give you this figure or you can just eyeball it and give yourself a good bit of extra capacity, if you are just going 3 feet out a window look at the 0.1 or 0.2 figures, if you are using flexible dryer vent maybe go with a higher 0.3 or 0.4. That 100 or 50 fpm figure is just a target point, many of the commercially produced booths fall short, on the other hand you really can't have too much air flow either (short of sucking the model into the filter ). When I designed my booth I calculated that I needed a fan in the high 300- low 400 cfm range, but got one rated at 485 cfm just to make sure I had enough fan.

I bought the Dayton 1TDR7 485 cfm, which was $144 last year. Most of the blowers Grainger sells assumes they are going into a fixed system so don't include a cord. They sell a heavy duty 8' cord that is easy to wire in for about $7 (#1FD82). I built the actual 24x24x20" booth from 1/2" plywood, the whole project came in right around $200 which is a bit less than where most of the smaller commercial booths start.

Edited February 20, 2010 by Aaronw

[Scott - Elm City Hobbies]

Mine is homemade booth, 100cfm bathroom fan, that pulls everything through a furnace filter and then extracted outside (see pictures)

Mind you, most of what I spray is Acrylic, I do spray lacquer for car bodies, however I also decant any spray cans into an AB bottle.

Not sure if lacquer is any less dangerous than enamel, but I am willing to bet that what actually ignited was the spray can propellant, and not actually the paint.

As well, not sure if the furnace filter has anything to do with somehow changing the paint fumes so they wouldn't ignite in the motor....who knows.

[CAL]

Could have been anything, gasoline vapors if he was in the garage. We just don't know and are assuming it was painting with the wrong fan/motor.

[AzTom]

Brush-less induction motors like those in bath and most hood fans can cause fires. If you have used one ten years, you are at a higher risk. The windings are exposed to the paint and over time the built up paint causes the motor to over heat and can cause the windings to short out. I have see many bath fans that have caught fire just from dust build up and hood fans from grease build up.

Get a fan that has the motor outside the airflow and use Metal vent piping to help contain a flash if you should have one.

I'm going to say a prayer for poor fellow that had the mishap as well as one for you guys that don't think it will ever happen to you.

AzTom

[Guest Johnny]

I have a friend that had a homade booth. He used blower motor and cage from an old car powered by deep cycle battery. Had it mounted into an air box above the booth. The filter slid in at the top of the booth just under the blower box. Was a pretty neat setup.

[beefheart22]

More importantly, people should be using respirators and safety glasses.

Second that. Even outside. Learned that the hard way when a gust of wind came out of nowhere and I ended up painting my face instead.

Horrible news. Best wishes to him and his family.

Edited February 22, 2010 by beefheart22

[cruz]

I have been using mine for over 5 years without any issues, I bought an inductor at Home Depot and built a wooden box around it, hopefully it will never catch fire or anything. I do want to invest on a squirel type fan later.

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Hopefully our friend can recover quickly, I will be praying for him......

[LO51 MERC]

I've had an airbrush for years and never used it. I'm currently giving serious consideration to using it, and using water based acrylics. I looked at the Pace paint booths...nice! I'd surely like to look at the one in the current issue of "Model Cars", but didn't find it in the ModelExpo site. Can anybody help? BTW, reading this entire post has been very interesting! Gary

[oversteer]

I got a spraybooth from ebay for $238 with FREE SHIPPING!!!!!!

It's a Paasche.It was delivered from the company in Chicago I believe.

Its rated at 240-280cfm,is this sufficient?

After reading this I figured cleaning it once a year would be a good idea?

Model #is HSSB-22-16

I will be using a respirator,saftey glasses and rubber gloves.

[Jantrix]

Another horror story. On trip to my local hobby shop I spotted a fellow in a full hip to toe cast speaking to the manager. When I was checking out I'd asked him what hapened to his friend. He said that he'd been using his old metal cased shop vac as exhaust for his spray booth. When the canister blew, it broke his femur, destroyed his knee and get this..........ruptured his testicle.

I have seen some squirrel cage style fans at my local used appliance store (from AC units) where the motor is out of the air stream. I was going to see of I can get one of those on the cheap and see how that works out. Opinions?

[Modelmartin]

I have been using a bathroom fan on my booth for almost 30 years now. Yes, The same one! I should think there was some other factor going on for your friends explosion. One can only speculate and I won't. Best wishes for his recovery.

[Chas SCR]

I got a spraybooth from ebay for $238 with FREE SHIPPING!!!!!!

It's a Paasche.It was delivered from the company in Chicago I believe.

Its rated at 240-280cfm,is this sufficient?

After reading this I figured cleaning it once a year would be a good idea?

Model #is HSSB-22-16

I will be using a respirator,saftey glasses and rubber gloves.

You should clean it more then that! I have a Pace what ever the middle one is that he sells, and I also lay down a sheet of celo foil on the pan to help with clean up.. I Clean mine after doing primer spay or even some times just after the color coat is down just depends on how dirty it is. Cleaner it is the least that the dust is blown up onto what you are painting. Also always keep a spray bottle of water next to it to spray in the air. The water collects the dust that you an not see and and brings it down and then you can paint with out the worry of dirt or ###### getting into you paint.

[59 Impala]

I built mine out of scrap plywood and a squirle cage exhaust fan that the company was throwing away because it was frozen (not working, locked up, bearing froze). I took apart the motor and oiled the bearing and it works just fine. Cost to me--------Zero. I use furnace filters and drier duck tubing to exhaust the fumes. Here is a pic of what it looks like.

Excuse the poor pic, it's the only one that I have at the moment that shows the whole thing. Dan

[envious8420]

i really wish this was a must read sticky. harry, pat, gregg???

[VVhiplash]

Am I missing something here? Since when is spray painting a model car a huge danger? I did these models as a kid and used to spray in my bedroom!

Now I just spray (maybe 10 minutes/week) in my workshop (basement room). Is there really a need for that much ventilation? I usually open a window and run a large standing fan. It's not like anyone smokes in the house...

I'm definitely uneducated on the matter. I do have young children so I want to make sure I'm not doing anything unsafe. Does this apply only to rattle cans or also airbrush?

Edited August 12, 2010 by VVhiplash

[Dave Ambrose]

I hope your friend makes a full recovery. Painting explosions are very scary.

Lacquer solvents are particularly flammable.

You need a certain minimum concentration of solvent fumes to get ignition. This usually happens in the exhaust duct, which is why the fan is so important.

Exposed brushes and paint vapors are an accident waiting to happen. Explosion-proof motors may have brushes, but their cases and bearings are well sealed to prevent any ignition from propagating outside the motor. Brushless motors should be fine. But just having a 12 volt fan is no guarantee of the motor being brushless.

Better yet, use an engine compartment ventilator for a boat. These are inline blowers, and ignition protected. They're intended to remove gasoline fumes from the engine compartment before starting the motor provides an ignition source. They run off 12V, and only cost about $35. West Marine has a couple of interesting candidates here.

I would take a second precaution of putting a metal screen between the fan and paint booth. This will prevent any flames in the exhaust duct from propagating into the paint booth. The screen must be metal, and preferably made from copper.

Aluminum or brass might be OK, but I'd test it first in a propane torch. Hold the screen over the flame. If the flame stops at the screen, it's working.

Be aware that the above steps will be of little to no assistance if you ignite something on the model or in the shop. Be mindful of your water heaters and furnaces. Personally, I wouldn't want either one in the same place I'm spray painting.

Edited August 12, 2010 by Dave Ambrose

[tbusch]

Let me add another issue of spray booths. If you have it in a basement and a older style furnace when you turn on the fan you need to have an outside air source, open a door or window,

A few years ago a friend of mine suddenly died, while this was not the cause of death the autopsy showed a high level of CO in his blood stream. The gas company was called to look at his condo and the first thing they pointed was the air booth, It was stated without an outside air source the fan is pulling air down the flue pipe.

The new high effiency furnaces I think do not have this problem

[mredzadventure]

I work in the Hazardous waste industry and we load some very flammable waste loads. Methanol, Acetone, MEK, Octane and the like. Some things we worry about are proper grounding during loading and vapor recovery. A static discharge can ruin your whole year. I know of 2 HUGE explosions over the last 4 years that were caused by that. Vapors are nothing to take lightly. We will use a compressed Nitrogen blanket during the loading process and purge the tank before. A little mix in the vent will reduce the chance of a explosion. It might be something to think about if you are using an old bathroom fan. I'm not sure how much a bottle would be to get filled .Just an Idea.

[VVhiplash]

I'm still interested to know if everyone here use a paint booth or not (casual modelers). If not, what precautions do you take?

[crazyjim]

I built a spray booth with plywood, furnace filter and a bathroom exhaust fan. Maybe I like living on the edge - I smoke and ride a motorcycle too!

[DRG]

I just recently got back into modeling and have been collecting all the different tools I will be needing. One of those was an Air Brush package. I figured I would build a paint booth using plywood, furnace filters and an exhaust fan. Admittedly I was thinking of using two bathroom type exhaust fans but after reading this post I will get an exhaust fan, (Dayton) from Grainger.

It may be a little more expensive but a whole lot safer. Thank you for posting this article.

[Don Wheeler]

I don't want to get into the discussion on fan types. But, if you keep the concentration of vapors below the LEL (lower explosion limit), you can have all the sparks you want and it won't explode. Here's what I think might have happened to the poor guy. He started spraying without the fan running. Maybe he was just intending to do a little touch up. Then he decided that, boy the fumes are getting a bit heavy. So he flips the power switch. The switch makes a spark, and Boom, explosion. Another possibility is that the fan wasn't moving enough air to keep the concentration low enough, maybe a dirty filter or no opening for incoming fresh air. In that case, static discharge could have set it off. You always want to have good ventilation before you start spraying.

Don