How dangerous is this.. who else does it?

[Bill Webber]

The thread down below on spray booths has me wondering who else may be skirting danger in a home made spray booth. And, how dangerous is it really?

I have (had) two spray boothes, both similar in design. Both are in outbuldings. Both use a pair of 1500 cfm attic fans. The fans are mounted low to the floor. In one case, directly in the floor with filters in front. In the second case in a 16" x 9' board that sets under a partly opened garage door. Both building are fairly large with the smaller one being 16 x 24 feet,. Both provide large inlet air openings. I always shoot towards the fans and filters. I have no special lighting or inlet filtering. I'm obviously at natures mercy when it comes to weather, heat, cold and humidity (and bugs). I use lacquer based finishes.

The fans are mounted low, because "Most solvent vapors are heavier than air and tend to collect in low spots." Curiously, many commercial spray booths have fans overhead, with both inlet and outlet overhead.

I've been using this setup for 15 years... hobbiest activities, with no problems. So how dangerous is this? Anyone have any stories about people that blew themselves up? Anyone else have a similar set up?

Be safe! :rolleyes:

[Al Willits]

Comm units exchange enough air that it probably doesn't matter where they are, where I used to paint at they were along one wall, in fact the entire wall was filters.
As far as safe, explosion proof motors would be a good start, but trying to make a OHSA approved spray booth might be more than what you want to spend.

When I was spraying motorcycles and such out of my garage I had the explosion proof blower motor and tried to use common sense after that.
No open flames, turning lights on or off, anything that might create a spark, I also made a paint booth design that allowed the exhaust blower to get as much of the flumes as possible.

Kinda depends on how much you want to spend.

Al

[Howard Acheson]

>> The fans are mounted low, because "Most solvent vapors are heavier than air and tend to collect in low spots." Curiously, many commercial spray booths have fans overhead, with both inlet and outlet overhead.


In fact, the newest thinking is for air to be moved into a spray booth from above and exitted from below. That way the fumes and overspray is directed downward away from the operator who tends to stay in cleaner air.

Just as with dust air filters, you always want the air pattern to be such that the operator in clean air. Avoid having the operator between the source of contaminates and the exhaust or air filtering device.

[Cliff Rohrabacher]

Tis prolly one of the reasons people go waterbased.

The tech is getting better.

I just tried some for the first time and liked using it and liked the result.

[Allen Bookout]

Like Bill I have always wondered how dangerous some of these setups are in reality. I have used all kinds of unapproved setups over the years with no explosion----yet. You would think that we would have heard more about actual exposions if they were as dangerous as the safety people make us feel. Anyone have any input with actual personal knowledge of accidents?

I am building a small booth now using an attic fan but am planning to only use water based products due to the fact that I do no know how dangerous using other products really is. To go with an approved booth you are looking at real big bucks that can only be justified with a full time paying operation that is out of the limits for a very small shop or hobby workshop. On top of that I do not think that they would be approved for residential areas where a lot of us work.

If I decide to use products other than water based I think that I will go ahead and use approved fans but will have to forgo the metal enclosure.

[Al Willits]

The idea for safety in a spray booth imho is to keep the vapor percentage below the lower explosive limit, old rule of thumb I heard was if you have to stop painting to see, your not moving enough air.
Make a pass and just before you start another one look up, see stuff hanging in the air, probably not enough airflow.
Not very scientific I know, but with most automotive finishes it seems to work.

Al

[Phil Pritchard]

I notice that no one has mentioned the need for sealed (i.e. explosion proof) lights, another commercial requirement.

[Allen Bookout]

Bill,

I failed to note that, like you, I have always had mine set up in a two car garage with a double door open on one end and a single door on the other end. I have sprayed enamel and two part urethanes but no lacquers.

[nic obie]

Bill,

I failed to note that, like you, I have always had mine set up in a two car garage with a double door open on one end and a single door on the other end. I have sprayed enamel and two part urethanes but no lacquers.


At the risk of getting the usual PC peeps here pissed...

I have sprayed many, many, many gallons of NC and CAB Lacquer in the same type of shop for more years than I want to admit. I do have a regular furnace squirrel cage type blower venting to two 8" ducts thru the roof. None of my lights are 'explosion proof' and I am sharing the space with a gas furnace and gas water heater. As I am lucky to live in a nice warm place, I just open everything up when spraying.

Listening to some here, you'd think just a couple of squirts with a rattle can will kill you.

:cool:

Folks have been finishing kitchens the same way for decades.

[Jim Becker]

Safety is nothing to joke about, Nic. Yes, many folks do things that are not ideal...that's an individual choice. But that doesn't discount the importance of talking about the right ways to do things that preserve your property, your health and perhaps even your life...

[Allen Bookout]

Safety is nothing to joke about, Nic. Yes, many folks do things that are not ideal...that's an individual choice. But that doesn't discount the importance of talking about the right ways to do things that preserve your property, your health and perhaps even your life...

Jim,

I know that you are talking about the ideal and safety which is fine but the problem is that some of us cannot afford the right way to do things all of the time. For us it is either do it the way that we can or not do it at all. No way could I justify the kind of money that a certified spray booth cost not being a professional unless there was a great deal of risk involved. I do not really know what the risk factor is. From my own experience I just get the feeling that the risk is not very high when having pretty good ventilation.

The other thing that I find noteworthy is that so far no one has come up with an accident report and I have never personally know anyone that has an explosive type accident while spraying.

I guess that it falls into risk management. So, thinking in these terms I would like to see some figures on explosive accidents per some figure and the circumstances behind each accident. Lacking this type of report I would like to hear from some members regarding some actual accidents and their evaluation of the situation at the time of the accident.

[Greg Funk]

For us it is either do it the way that we can or not do it at all. No way could I justify the kind of money that a certified spray booth cost not being a professional unless there was a great deal of risk involved. I do not really know what the risk factor is. From my own experience I just get the feeling that the risk is not very high when having pretty good ventilation.

The other thing that I find noteworthy is that so far no one has come up with an accident report and I have never personally know anyone that has an explosive type accident while spraying.


If you don't know what the risk factor is how could you 'feel' that the risk is not high based on your experience?

First hit on 'the google' http://www.texas-fire.com/blog/?p=851 a man badly burned spraying lacquer in a kitchen.

I think I'll stick with water based finishes...

[David Rose]

I think there is more hazzard from breathing the fumes than from explosion. A few years ago someone, I can't remember his name at the moment, tried to light paint fumes and even solvent as it was sprayed through a normal fan. There was not enought concentration for him to ignite it even with a propane torch. The residual effect of the fumes on the body is another subject. Lots of painters have quit due to various health problems that they thought were related to painting.

David

[Phil Pritchard]

I'm not really worried about explosions, but I am woried about fires. From what I've read using motors which are not explosion proof is the biggest fire hazard, and once a fire starts in a spray shop it has lots and lots of accelerant to feed it. The commercial requirements for lighting and static earthing is because volume sprayers are at much greater risk of an explosion than the small shop, but the cost of enclosing your lighting inside boxes is pretty minimal, as is the cost of moving your light switches outside so that the arcing can't start anything. Incidentally if your extraction is up to par you should never have enough combustable mixture in the shop to start anything. And how many people here do woodworking or spraying in a shop where they don't even have a fire extinguisher, I wonder? You don't have to buy the industrial rated stuff at all, but it's always worth seeing how the big boys do things and maybe copying some of the safety ideas.

As someone else has stated, the biggest single danger is breathing overspray - but then who sprays without an adequate mask?

Phil

[Al Willits]

I suppose every post should start with, You need a OSHA approved booth or you may blow up.
Everything after that would be your taking a chance on doing your self in, that should keep everybody happy.
Now not having the space or money to do this, some of us have to compromise a bit.
You can not have a explosion if the vapors are below or above the explosive limits, ain't gonna happen, ask any fireman about the triangle, oxygen, fuel and heat need to be at certain percentages to have fire.
Least wises in the real world.

If you move enough air, the only place (never say only...I know) your liable to get that would be at the exhaust fan, move enough air and it wouldn't even be there.
The only reason I bought an explosion proof fan is another painter buddy had one of the two 1/2hp basic exhaust fans short out and the paint in the squirrel cage blower caught fire.
He does automotive painting for a living and probably paints more in a year than most of us will in a life time.

I keep hearing ya can never spend to much on safety, well I wished I had the disposable income some must have, but unfortunately I don't, so like a lot of the other people I know, we have to do the best with what we can, or just sit in front of the TV, other than rotting the mind, it's pretty safe there...:D
imho, this whole thing can be summed up with the word, airflow.
Well...that and a good respirator..:)
Al.....who's off for his second cup of coffee and will come back and try to figure out what he just posted....

[Jim Becker]

I know that you are talking about the ideal and safety which is fine but the problem is that some of us cannot afford the right way to do things all of the time. For us it is either do it the way that we can or not do it at all.
Relative to this topic, I strongly disagree. You have the clear option to use finishes that do not have the explosion risk. The water borne finishes available today, especially when combined with hand application of oil and shellac as first steps for "grain popping and warming", allow you to spray durable finishes that have many of the same qualities that the more dangerious mateirals, such as NC lacquer, have without the risks. You still need reliable ventilation, but don't need to spend the money on expensive "explosion proof" fans, lights, etc.

This is a choice you can make...and one that I made several years ago since I also don't have the place nor the funding to put in a "pro" spray booth.

[Cliff Rohrabacher]

Listening to some here, you'd think just a couple of squirts with a rattle can will kill you.


Amen Brother.

The ratio of flammible vapors to oxygen must reach a threshold for a spark or open flame to do anything at all.

Which begs the question: How much spraying will you be doing?
If all it is is a piece or two every month and you have some ventilation you are probably golden.

Of course if you over do it and end up with a fire, you may have an insurance problem collecting and then, and you may find it tough if not impossible to ever get fire insurance again.

So ya gotta use yer noggin.

[Rob Blaustein]

Relative to this topic, I strongly disagree. You have the clear option to use finishes that do not have the explosion risk. The water borne finishes available today, especially when combined with hand application of oil and shellac as first steps for "grain popping and warming", allow you to spray durable finishes that have many of the same qualities that the more dangerious mateirals, such as NC lacquer, have without the risks. You still need reliable ventilation, but don't need to spend the money on expensive "explosion proof" fans, lights, etc.

This is a choice you can make...and one that I made several years ago since I also don't have the place nor the funding to put in a "pro" spray booth.
Along these lines--folks might want to check out Jerry Work's "Users guide to waterbased finishes" on the Target Coatings website (http://www.targetcoatings.com/manual.html). Jerry is a professional woodworker who only uses waterbased finishes now (and only sprays). He's also an avid Festool fan and has written excellent manuals for some of the Festool tools. Target finishes have been discussed here many times, and Jerry has been mentioned as well, but this looked like a good spot to bring it up again.

[Steve Jenkins]

A couple things regarding explosion proof fans and lights. You can make an approved spray booth by simply using two layers of 3/4 sheetrock all around.

the lights can be any kind as long as they are outside the booth. I used 8' florescents above the ceiling with a piece of wire reinforced glass sealed against the inside of the ceiling with closed cell foam weatherstripping and an aluminum frame to support the glass. The lights just layed on the ceiling.

If you look at the blower in commercial spray booths the fan (tubeaxial) is in the airstream but is belt driven and the motor is outside the exhaust duct and booth so it is in clean air. Also the fan is aluminum (non-sparking).

switches and any outlets need to be outside the booth.

This is simplified somewhat and you would need to check with your local code enforcement to get details but like many other things getting a homemade booth greentagged is pretty tough. A few years ago I built a spray room and had the devil's own time trying to get definitive answers on the requirements.
I finally just went to the local fire-inspector who happened to be a very reasonable type and asked what he wanted to see when he came by for his annual inspection.

In the past I have sprayed A LOT in a warehouse with a typical ceiling mounted gas heater running. the flames on the heater changed color a bit if I was spraying a lot and that's about all. It seems that most eplosions occur when you have an ignition source near the floor ie. pilot for hot H2O. You can't detect the buildup of vapors there and suddenly BOOM.

I agree that safety is one thing that should not be short-circuited and over the years many of us do things that we wouldn't recommend. Good "not so common sense" and that certain level of comfort in what you are doing are two things that go a long way toward preventing accidents.

[nic obie]

Relative to this topic, I strongly disagree. You have the clear option to use finishes that do not have the explosion risk. Oil and shellac as first steps for "grain popping and warming", allow you to spray durable finishes that have many of the same qualities that the more dangerious mateirals, such as NC lacquer.


Well Jim,

I have to disagree with you.

More houses have been burnt down because of wipe on finishes such as Watco and other oil based finishes like tung and linseed oil than anything sprayed.

Am I wrong about this?

[Jim Becker]

There are many hazards, Nic...spontaneous combustion on rags used with wipe-on oil finishes obviously qualify, so we absolutely agree on that risk. No brainer on that one!

I need to add to my previous...it's not just about "explosions". Home-shop situations also need to account for the real danger that fumes have to both the woodworker and others, especially if the shop is physically attached to or part of the house. Lacquer fumes, in particular, are nasty...

Folks who argue that they "have done it for years with no problems" are not teaching others (especially newbies) best practices nor acknowledging that there might actually be better ways to do things. For that reason I must continue to point out that there are choices available that mitigate the risk without breaking the bank nor giving up quality and capability. (I am certainly guilty of doing some things that I would not recommend to others, too...but that is the key point...I will not recommend them to others)

[Brad Olson]

You should be wearing respirators too with waterbased finishes.

They are just as hazardous for breathng, just not as explosive.

Because I am a chemist and understand how to mediate risks with solvent based finishes, this is what I prefer. I'm not sure that organic repsirators will work for the chemicals in waterborne finishes or not, of particular worry is the acrylic resins. The solvents too may be of some risk as well, but it is hard to say since the MSDS's are vague. You should note that the solvents for WB finishes are ether or alcohol derivatives (depending on the brand), none of which are good for you to breathe. I would aruge that in fact they are more toxic to you then the solvents used in conventional finishes, mainly because inhaltion risks are largely unknown.

From my perspective the only advantage of a water based coating is less risk of fire/explosion, not a "healthy" or "safer" finish to spray.

[Rob Blaustein]

You should be wearing respirators too with waterbased finishes.

I would aruge that in fact they are more toxic to you then the solvents used in conventional finishes, mainly because inhaltion risks are largely unknown.


Brad-I agree about the respirator advice. But I'm not sure I follow the logic of the next point. If the risks are unknown, how can you argue that they are more toxic? They may be, but they also may be less toxic. Or of equal toxicity. But if, as you say, they are ether and alcohol based, isn't there a pretty long history with these solvents and aren't the risks known?

[Allen Bookout]

You should be wearing respirators too with waterbased finishes.

They are just as hazardous for breathng, just not as explosive.


I am glad that you posted this as I am planning on using some water based finishes and because it gets so hot here I tend to not wear a respirator if I can get away with it. I know that I cannot get away with it with the dangerous stuff. I am sure that I had in the back of my mind that it really was not that bad using the water based products. Now I will approch the job with a new outlook.

[Brad Olson]

Brad-I agree about the respirator advice. But I'm not sure I follow the logic of the next point. If the risks are unknown, how can you argue that they are more toxic? They may be, but they also may be less toxic. Or of equal toxicity. But if, as you say, they are ether and alcohol based, isn't there a pretty long history with these solvents and aren't the risks known?

That is the way you treat something that looks bad with unknown risks.

The ether and alcohol derivatives are likely fat soluble and may have a long half life in the body (kind of like dioxins). Typical VOC solvents usually have short lives in the body because they are quickly oxidized by the liver into water soluble compounds that exit the body quickly.

As to the risks of the ether and alcohol derivatives, no the MSDS's clearly indicates there is little known toxicity information on them, likely because they were synthetically made specifically for the finishes or have not had a lot of use in products previously.

Since to me the compounds look bad and have unknown risks, I treat them as more toxic than things wtih known risks.

[Jim Becker]

Brad, my understanding is that the active solvents in the water borne finishes are not really that different than in other types of finishes outside of there being a lot less of them. (Remember this is "water borne" not "water soluble"--the water is used to carry the finish to the surface, but is not actually involved in the curing of the resins, etc.) That said, all of the water borne finishes I've used (outside of the rare MiniWax WB Poly in a pinch) have coding on the outside of the can relative to VOC and other hazards. This color coding is quite useful for planning personal protection. But even if there is zero VOC, wearing the respirator is still a good practice because particulates that get suspended in the air while spraying are not something you really want to breath, either...

[Brad Olson]

Jim,

That is close, the big difference between a WB finish and a oil based finish is that the WB finish will have some sort of emulsifier. These are what I worry about most for safety beyond the regular VOC's already in the finish. These are the ether and alcohol derivatives that I was refering too. Some of these alcohol and ether derivatives may or are safe, buy many are not.

What these do is allow the transition between the hydrophobic (water hating) VOC's and the and the the water or other alcohol based solvent.

The problem with some of these is that the mode of toxicity is much different than that of a VOC. i.e. you won't get dizzy or a headache from too much exposure and may no know when to stop.

This like the poster above is why I warn, is that most people just assume WB finishes are safe because they are water bourne or based and this simply is false.

This is also why a pregnant woman shouldn't paint the new nursery. Her baby is exposed to a massive dose (relative to size) of the chemicals at critical developmental time.

[Martin Shupe]

Good discussion everyone....

Steve, your light solution sounds smart, but how did you change the light bulbs? This is a serious question, not a joke, and I can't figure it out.

Sometime in the next year or so I'll be trying to design and build my shop, and a small spray booth is in the big plan.

While I mostly use Waterlox now, I would like to be able to spray shellac. Also I really would like a room that does not have the dust headaches I have been dealing with in my open garage shop.

I am not sure I will ever spray lacquer, but I want to be able to do so if I change my mind.

Thanks for all the helpful tips and discussion.

[Steve Jenkins]

Good discussion everyone....

Steve, your light solution sounds smart, but how did you change the light bulbs? This is a serious question, not a joke, and I can't figure it out.
Martin, I had space above the room to access the lights. I made the room with 10'ceilings and had 7 feet of clearance above that. Big warehouse space. The other way would be to hinge the glass cover so you could swing it down and change the tubes from below. Or if you don't want to hinge it just remove the screws that hold it in place and set it aside. The aluminum frame had the weatherstripping glued to it and was in turn just screwed to the ceiling joists.
When are you going to make a day trip and come visit?

[Russ Filtz]

I think this should be an episode of Mythbusters! They did one similar where they tried to explode a house due to too many bug bombs. Couldn't get it to ignite! I'm thinking they used too many (or too few) and didn't hit the explosive limit right.

A lot of factors have to be just right for a gas explosion. A lot of setups may be flirting with disaster and not even realize it. The old "hey I've done it a hundred times like this", but it's the next one that gets you!

[Bart Sharp]

On this topic, let me pass along something I've heard and get your opinions. I have been told that the correct way to ventilate a spray booth is by having a fan or fans blowing in to the booth, not out. The inlet side of the fans is filtered to prevent dust being blown in, and air exits through filtered exhaust openings to keep airborn finish particulates from being spewed out. There are supposed to be two advantages of a "positive pressure" setup like this versus the "negative pressure" situation caused by having exhaust fans.

One, the fans are always operating in clean air (assuming they are turned on before the spraying begins, and that the entire inlet/outlet system is big enough to prevent fumes from building up). That should greatly reduce if not eliminate the potential for an explosion being set off by the fan motor.

Two, it helps reduce potential dust problems. Given that it would be difficult to guarantee that a booth were completely airtight, a negative pressure differential could pull dirty air through any little crack, not just nice clean air through the inlet filters. By positively pressurizing the booth with fans blowing in, no dirty air can sneak in. The only place the air enters is through the fans, and it is easier to ensure that they are properly filtered and sealed relative to the entire structure.

I've never built one, but it seems logical enough as it was explained to me that I'm pretty well convinced it's the right way. What say ye?

[Allen Bookout]

I am waiting for a response to Bart's post as I am just starting to set up a temporary booth now. Please hurry!

It sounds logical.

After thinking about it for a while I am thinking that it would work if your whole exit wall was filters. Otherwise it might just pile up overspray inside the booth.

[Bart Sharp]

After thinking about it for a while I am thinking that it would work if your whole exit wall was filters. Otherwise it might just pile up overspray inside the booth.

You would have to give some thought to the CFM that the fan is pumping in relative to the amount of air that could flow through the exit filter area that you have, but I doubt it would be anything as radical as having an entire wall of filters. Certainly wouldn't hurt, but I don't think it would be necessary. I'll bet there are tables out there for filters that would help answer this.

Like someone else mentioned before, I'm imagining the fan located up high behind the operator with the exhaust opening low on the opposite wall to keep the operator in clean air and take advantage of the heavier-than-air solvent vapors and finish particulates.

[Brad Olson]

You do have to be careful with a positive pressure booth.

Mainly, if you have a leak, the overspray will go somewhere you don't want it to go.

I personally would not recommend a positive pressure set up unless you shop is in a dedicated building and you do some serious engineering to make it work properly.

The usual way to design environments for hazardous fumes is to put them under negative pressure to a common controlled outlet. This way if there is a room leak, you know where the fumes are going.

For example Bio Safety labs are always under negative pressure to a common filtered exhaust. The reason being if something escapes, it goes to the filtration stack and not out the bottom of doors into the office space.

On the opposite side are Laminar flow environemtns which are under positive pressure. This is for cleanliness of the environment, but should never be used for working with hazardous materials.

[Allen Bookout]

That's good information Brad. Thanks!