Dangers of On-Site Finishing

Health and fire risks that accompany improper ventilation. September 20, 2004

We build homes and finish our trim and base on site. The usual schedule included spraying two coats of Magnamax on our trim, base, and interior doors. We do not have a spray booth, so we typically set up in the largest room in the house, open a few windows, throw on our masks, and spray away. Are we playing with fire here... literally? I have read quite a few posts about spark-free fans used in spray booths. Where could I find some of these for a reasonable price? We usually spray for a maximum of two hours and then leave the house for lunch or for the day so that it can air out.

Forum Responses
(Finishing Forum)
From contributor R:
I think you might be flirting with disaster. Please get yourself a fan that not only has a non-sparking blade, but that has a fully enclosed motor as well. These fans are made for using in a hazardous location and can be purchased at a tool supply house like WW Grainger.

From contributor D:
Also, don't forget about the formaldehyde you are breathing. Even though it is an E-1 standard paint and the amount of formaldehyde in the paint doesn't have to be reported on the MSDS, it is still there and off-gassing even though your trim is dry.

From contributor J:
Good advice about the fans and off-gassing. I really need to stress checking on pilot lights for water heaters, gas ranges and heaters. I'm not even mentioning putting your stain rags in water, or other contractors smoking on the job site. A couple quick tips - tape off electrical outlets, do not paper over the overhead spotlights used in a lot of the new additions, etc. They get real hot and with any lacquer to help fuel the paper, you'll be sorry! One last thought - if stripping, be careful with lacquer thinner and steel wool making a connection on an outlet or light switch (don't ask me how I know). Hope you know the E.P.A. regulations for your area!

From contributor B:
Some very valid points have been made. You are loading a room with explosive vapors. Even a static electricity spark could be disastrous. Also consider the fact that a carbon respirator in that environment is basically worthless.

One other thought; just like riding a motorcycle, you may be driving perfectly safe. It's the other guy that is going to get you. Never assume that other people are going to heed your 'no smoking' or 'do not enter' signs.

I second the call to be safe!

From contributor E:
Just FYI. A newly constructed house in our neighborhood was having its woodwork finished. It happened to be the middle of winter so it was very cold here in Michigan. They sprayed everything up, cranked the furnace to 80 so everything would dry real nice, and left. It didn't take very long for the house to literally explode. In fact, when all was said and done, the only thing left of the house was the two story brick facing.

From the original questioner:
We use toxic dust respirators. We cannot taste or smell anything when using them so we assumed we were okay. In your opinion, is this assumption wrong? I'm looking into getting a non-explosive fan to help disperse the fumes out of the windows faster. We are based in Wisconsin, so the danger of having the furnace running is definitely there in winter. Do you think that the solvent based products are worth the risk in our environment, or should we give up and go to waterborne? It sounds like M.L. Campbell's waterborne lacquers are pretty comparable to Magnamax...

From contributor B:
The respirators you are using offer no protection against vapor, thus the name toxic "dust". Your nose gets desensitized to a particular smell after a short exposure. Go outside for a breath of fresh air, then come back in and you will definitely smell the difference. The only respirator suitable in that type of environment is an "air supplied" respirator. They pump in outside air, via hose, to a face mask and can be very expensive and cumbersome.

Waterborne sounds like the perfect solution to your problem. They won't give you quite the same performance as Magnamax, but will be more than acceptable for your application.

From contributor L:
We use Sherwin Williams Kem-Aqua water borne finish, sealer and their stain base. On tight grained woods you can get a good finish; on ring porous woods it's not as good. It takes considerable practice to get good at spraying it. There is a tendency to put on too heavy of a first coat. On ring porous woods, a coat of shellac first helps, or use a wash coat even under stains.

From contributor W:
The explosion-proof fan is a must. Cross-ventilation works the best with two fans. One blowing in and the other blowing out. There is only a very small risk of explosion, but it is there and the appropriate precautions must be taken. For solvent based products to explode, certain ratios of fuel to air must be met. The concentration of fumes has to be very, very high to be able to ignite. I have seen posts on this forum discussing heating finishing rooms with torpedo heaters with no ill effects. The key is to keep the flame on the supply side of the flow and to keep the fumes pumped out via exhaust fan. The fumes simply will not burn until a high concentration has built up. Keep the air moving and all will be well. As long as the air has a low concentration of fumes, a respirator with carbon filters rated for paint fumes is sufficient. Another way to keep the fumes down would be to switch to a portable AAA sprayer or a portable HVLP rig. Less overspray in the air.

From contributor B:
Your greatest potential for disaster lies not in the piece you are spraying now, but rather in the 50 pieces that you have already sprayed and are gassing off. AAA will reduce your immediate overspray, but it's still the "solids by volume" of your finish that is going to determine how much solvent you ultimately are going to release back into the air.

I agree whole heartedly that air flow is critical, but you have to realize that a living room is not a spraybooth. You can have corners with pockets of vapor that can be intense enough to ignite. Let's also look at the fact that there are also flammable liquids and wet mouldings laying around. Do you have a fire extinguisher available and do you think it's big enough to put out what could potentially be on fire?

I think the final perspective on all of this is the effect on your health. Do you change your respirator cartridges every day? Do you realize that your skin is your body's largest organ and that you can absorb considerable amounts of solvent vapor through your skin and eyes? What would you do if a year from now an employee develops a cough? Do you think your safety precautions would be sufficient to protect you in a lawsuit? Do you carry enough insurance to cover the structure you are working in? Does your insurance company know what you are doing? If not, they may not pay a claim even though you are paying the premium.

Hey - I don't mean to go nuts here, but after all, it is a business; your life and your livelihood. A smart business person looks at the risks as well as the profits. For years my company specialized in the restoration of historically significant buildings. I did extensive safety research through insurance companies and organizations such as Underwriters Laboratories before I exposed myself to potentially millions of dollars of liability. The most important thing I learned is that you never underestimate your potential for disaster.

Waterborne... it's a good thing.

From the original questioner:
Contributor R, you have definitely made me think about a few things that haven't crossed my mind before. What M.L. Campbell waterborne system comes the closest to look and performance of Magnamax? I have posted this question before and the only specific answer I got was to use SW waterborne over one coat of Zinzer shellac to reduce grain raising. I've been on M.L. Campbell's site and it looks like they have a few different waterbornes. I want the hardest finish that can be sprayed from an HVLP gun, and I need a descent pot life since we usually spray different items at different times and don't want to run to the supplier every day (Magnamax was perfect).

Again, thank you for all of your help. Your posts will result in major process changes in my company.

From contributor B:
Try the Ultastar clear and sanding sealer. There is also the Polystar pigmented and primer for painted finishes. Both have an unlimited pot life.

I have to tell you that I probably wouldn't get on my soapbox if I didn't have the experiences that I have. We had tens of thousands of dollars invested in our explosion-proof ventilation systems, air supplied respirators, fire suppression equipment and safety training; yet at the end of every job, I joked that "we lived through another one." One day I saw a picture in the newspaper of two painters standing on the ledge of a 12 story building with flames shooting out of the window next to them. I told myself that this could have been me, and I haven't finished on-site since.

From contributor J:
I don't see the need for you to shy away from field work or be limited in your use of solvent based stains or topcoats. Inevitably certain jobs need to be done in the field. A double filter spray mask (charcoal and pre-filter type) are pretty effective eliminating harmful vapors breathed in. That said, do yourself a favor and learn the proper care and handling of your respirator.

From contributor D:
I do Environmental Compliance for my company and I just wanted to get the word out about formaldehyde. As I stated in an earlier post, the formaldehyde in Magnamax will still be off-gassing even though the product is dry. That is especially important to know because if they are in an enclosed area, they still are breathing the toxin. And we both know they won't be wearing masks while installing.

I wouldn't want to be breathing that. Now, if they were spraying and waiting for a couple of days, it wouldn't be as bad, but most products with formaldehyde still off-gas for 30 days.

From contributor J:
Hopefully the work they are doing is already installed and at the end of the completion schedule. Also hoping that the jobsite is not sealed up after finishing is completed. Off-gassing of formaldehyde or other solvents is the dark side of finishing - acute exposure. The side effects probably still aren't totally known. That's why the Euros are way ahead on this learning curve - 2k poly doesn't off-gas the next day.

Don't assume, since you're working with water based finishes, that there are no health hazards either.

From contributor D:
Absolutely agreed upon there.

My only gripe about the 2kPU is the isocyanates used in the hardener. Haven't had a chance to check out a 2k WB poly yet, but I am sure I will look at an MSDS soon, now that this is in my brain.

Isocyanates are compounds containing the isocyanate group (-NCO). They react with compounds containing alcohol (hydroxyl) groups to produce polyurethane polymers, which are components of polyurethane foams, thermoplastic elastomers, spandex fibers, and polyurethane paints. Isocyanates are the raw materials all polyurethane products are made of. Jobs that may involve exposure to isocyanates include painting, foam-blowing, and the manufacture of many products, such as chemicals, polyurethane foam, insulation materials, surface coatings, car seats, furniture, foam mattresses, under-carpet padding, packaging materials, shoes, laminated fabrics, polyurethane rubber, adhesives, and other polyurethane products.

Health effects of isocyanate exposure include irritation of skin and mucous membranes, chest tightness, and difficult breathing. Isocyanates are classified as potential human carcinogens and are known to cause cancer in animals. The main effects of overexposure are occupational asthma and other lung problems, as well as irritation of the eyes, nose, throat, and skin.

From contributor B:
Did you know that when you bite into an apple you release about 2ppm of formaldehyde? MagnaMax meets the European E1 standard of omission of less than 1 ppm of free formaldehyde during its cure cycle. It's HAPs free, also.

The Europeans have historically looked at formaldehyde as the real bad guy and isocyanates as a harmless byproduct. Only now are they having second thoughts as more of the people who are exposed to it long term seem to be developing reactions to it.

Let's face it - none of it is good for you. Health problems can show up years after exposure. We have to teach people to protect themselves and encourage/demand manufacturers make products safer. It isn't easy, comfortable or cheap, but it is our responsibility. Rather idealistic, I know, but we have come a long way... a long journey is still ahead.

From contributor D:
Because manufacturers do not have to report that small amount of formaldehyde on the MSDS's, some customers use that in their decision making about what products they will use in their shop. We report all Haz Chemicals even if we don't have to. We have lost some customers because we choose to inform the end user what they are really getting in their product. One customer came right out and said "the only reason I am switching products is because of the formaldehyde issue." That customer still buys our stains but not our topcoat. I believe the ability to not report something really gives the customer a false sense of security.

Most of the products I have meet the E-1 standards and are HAPS free or low HAPS, but we still choose to report. And with the compliance reports I do for my customers, the formaldehyde is listed. For some of my bigger customers that buy 20,000+ gallons a year, it makes a big difference.

From contributor S:

One last word on ventilating a house. Explosion proof fans are not needed if you use them only for positive air flow only.

Set up your spray area close to a back door and set up a fan at the front door blowing into the house only. The fan should be at least 1400 cfm. We made a narrow plywood box on castors and installed two furnace type fans which work great.

We only spray onsite with Air Assist Kremlin and we do not thin our products with lacquer thinners - we spray out of the can.

We just sprayed onsite in a museum with our Kremlin, with no ventilation available, using a pre-cat lacquer.

We had No Fog Cloud after spraying like we used to have with Binks Mach 1 HVLP. HV means High Volume of air and Air Assist is a whisper compared to my old system.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
With regard to M.L. Campbell or any other acid cured product and formaldehyde, keep in mind we're talking about two different things here.

There is container formaldehyde, which is "in" the product. Typically it is a very small part of a resin that may be a small part of the formulation. This is what is reportable/not reportable depending on the amount contained.

Free weight formaldehyde on the other hand is the formaldehyde that is off-gassed during cross-linking. Think vinegar and baking soda. You mix the two together and you get CO2. In this case the reaction is releasing formaldehyde. That is the formaldehyde that is concerned with E1 regulations.

E1 doesn't have anything to do with amount of formaldehyde, so much as amount released/period of time. A coating can be E1 and release more formaldehyde than an E2 or above product.

Let me explain. Take a cup and poke a hole in the bottom. Now pour water in very slowly. If the water is poured into the cup slower than it runs through the hole, the cup will never over-flow. Now increase the rate of your pour. Once your pour is faster than your hole can let the liquid through, you'll over-flow.

If I spray a board, the solvents evaporate and the cross-linking begins. Free weight formaldehyde is being released from the reaction. If it is released slowly enough so that it can dissipate before if hits you in the nose and eyes, you're not going to get that fun red burning sensation. If it releases formaldehyde quicker than the environment allows for its dissipation, exposure will be noticed.

Product A releases X formaldehyde.

Product B releases 1.5X formaldehyde. (66% more)

If A releases its formaldehyde over 1 week and B over 30 days, B is going to rank better on the E-scale. It is not simply about quantity.

The biting an apple thing is disingenuous and not at all accurate. If we're talking about the tiny bit of formaldehyde contained in the pail when you buy it, it's not so bad, but when we're discussing the actual issue, it's a very poor and misleading example.