Running the Criteria Gauntlet
The first time I was presented with someone in need of an estimate to protect a paint booth was many years ago. I looked to others in the office for guidance, but I seemed to mostly get answers that involved “I think,” “I’m pretty sure,” or “Hmmm.” None of these responses made me feel very confident about providing a price estimate to properly sprinkler a paint booth. I figured the next step would be to check NFPA 13, Standard for the Installation of Sprinkler Systems, for some answers, as normally a little code reading would at least point me in the right direction. My thought at the time was: “It’s just a little 20 ft x 30 ft box on a floor plan that says ‘paint booth here’ – it can’t be too hard, right?” I found out several hours later this was not the case and my thought became, “Man, I’m glad I didn’t just slap six sprinklers in this thing off the overhead system and send it out!”
The first place to start, like always, is to determine the appropriate hazard classification. That pointed me to section A.5.4.2 (2) Flammable liquid spraying as an Extra Hazard (Group 2), 0.40 gpm/2500 ft2. Wow, that’s a lot of water! At the time, I hadn’t really dealt with much outside the ordinary hazard section of the standard so back to the book I went for some more research.
The first thought I had was: “How do I determine if this is indeed ‘flammable liquid’ that they are spraying inside this booth? What qualifies something as a flammable liquid?” I looked up flammable liquids in the back of the book which guided me to Section 22.2, which didn’t prove to be very helpful. The reading up to this point in my investigation pointed me to NFPA 30, Flammable and Combustible Liquids Code, and it seemed to me that I might need a Ph.D. to figure this out with words like “closed-cup flash point” and “boiling points.” I’m not sure about any of you, but I ended up in this career field, first in the field for seven years and then in the office, at least partially due to my lack of interest in attaining a Ph.D. and learning chemistry.
At this point I called time out and got on the phone with some people I knew who had far more experience than I did. They were at least helpful in cutting out some time in the research process by telling me that if it’s a commercial paint booth, it’s probably a safe bet that it is a flammable liquid being sprayed and pointed me to the next section, 22.4, which classified paint booths as extra hazard (Group 2). On a side note, I did learn later in my career that finding these crazy scientific terms wasn’t as hard as it appeared at the time I first read them. It turns out that if you find an MSDS sheet (or now what’s called an SDS sheet) on the product, the “scientific name” is usually listed. However, finding it the first time on a product can feel kind of like a game of Where’s Waldo for some products.
With my hazard classification determined, I moved on to sprinkler selection, which led me to K-factor of K-11.2 sprinkler because the design density was greater than 0.34 gpm/ft2 (although it’s guidance from Chapter 12 for storage). I thought I was almost home after the hour or so detour, getting a quick reminder of why I didn’t opt for advanced chemistry classes in college. Now off to spotting sprinklers on my dashed line indicating “paint booth here,” I decided I had better do a little more reading on these booths now that I saw that section 22.4 proved to be helpful on the last problem I ran into. Upon reading more in this section it seemed that NFPA 33, Standard for Spray Application Using Flammable or Combustible Materials, was referenced quite often so I had better figure out what the heck that was. I looked it up and came to find out that there is an entire standard for these things! By this time, I’m sure I was beating my head on my desk as whatever else I had planned for the rest of my day was clearly not getting done.
I decided I had better finish reading this section in NFPA 13 before moving onto another standard entirely. I quickly gained some new insight reading the rest of Section 184.108.40.206 by learning that I needed to have the sprinklers protecting the booth controlled by a control valve. It also appeared that sprinklers needed to be installed in ductwork per Section 220.127.116.11, but which ductwork was still a mystery to me. I continued digging through NFPA 13 to find out exactly which ductwork needed coverage. All that Section 18.104.22.168 alluded to was what to do when I needed to cover ductwork – nothing about which ducts needed to be covered. Intake ductwork? Exhaust ductwork? Plenum spaces? I couldn’t find the answer in NFPA 13, so I quickly put that thought on hold as perhaps my upcoming NFPA 33 research could help answer that question. I continued my NFPA 13 research and determined the sprinklers installed in these areas would need to be readily accessible, and if they were exposed to freezing conditions, needed to be dry- type sprinklers per the subsequent subsections. All sprinklers also needed to be protected from overspray by paper or cellophane bags. I learned a few things through this research but I figured I better look into NFPA 33 to see what that was all about. I was expecting hours of reading, but to my surprise, it was short – and upon looking through it – I found that there was very little information there regarding installing sprinklers in a paint booth. So little in fact, that it wasn’t helpful. It seemed to be a reprint of what I had found in NFPA 13. This shouldn’t have been a surprise since the information was brought into NFPA 13 from NFPA 33 using NFPA’s extract policy.
At this point I still had several questions, but I thought I had most things figured out as far as coverage goes. The remaining high point I needed to cover was what ductwork needed coverage. From where do I determine that? I decided at that time to make some calls again to the people I talked to early in the game about the flammable liquid definition to try to get this thing moving again. Everyone I talked to pointed me in the same direction: that all exhaust ductwork needed coverage, but intake air shouldn’t need coverage if the air was not getting recirculated from the exhaust air. I asked each of them where exactly they got this information, and the response from each was very similar and something in line with, “Heck I don’t know man, that’s just what you do!” usually followed by, “You ask too many questions!”
In writing this article, I am reminding myself that there is still very limited information on paint booths anywhere out there. When I decided to write this article, my thought process led me to a fear of making sure that anything I wrote was 100 percent correct and accurate. In that process, I pulled out all my paint booth stuff so I could point everyone to exactly where this stuff came from. Unfortunately for me, that just isn’t possible. This is a good reminder to myself of some of the questions I wanted to help clear up when I was appointed to the NFPA 33 committee last year, representing the American Fire Sprinkler Association (AFSA).
After that short detour, let’s get back to the situation at hand. I had a paint booth to try to sprinkler after coming up with my overall scheme of how I thought this needed to be done. I had an extra hazard (Group 2), K-11.2 or larger sprinklers, an isolation valve for this system, sprinklers in the spray area needed to be accessible for the reason of placing removable overspray protection on them periodically, and I needed to protect the booth area and the exhaust ductwork. Hard part over, back to my paint booth!
Wait a minute, back to my dashed line where the paint booth goes, darn it! At least I knew how to sprinkler it once I found out what the booth looks like. After digging through the plans, it became apparent that no plans existed of this “mystery booth” in the plan set I received. I was fortunate on this project as I was dealing directly with one general contractor (GC) working directly with the owner. After a call to the GC, I was pointed to the owner as the paint booth was an “owner-supplied piece of equipment” so I would need to contact them. A call to the owner in this scenario yielded a pretty detailed plan of the paint booth. This information provided a big relief that I didn’t fully appreciate until a later date when I bidding on a “paint booth here” dashed-line scenario in the plans and specifications for another project. I had very limited time to price it, and often times had no knowledge about the paint booth that was getting purchased. I still needed pricing for the sprinkler system installation within it.
With plans in hand on the booth and a manufacturer to call if I had questions, I found that the dashed line wasn’t one 20 ft x 30 ft rectangle; that was just one part of it. Adjacent to it was also a small mixing room that was 10 ft x 12 ft with a bunch of equipment on the side of it that didn’t make a whole lot of sense from looking through the plans. I made some calls to the manufacturer and got an education in paint booths that helped me understand the basic operations of two styles of paint booths, which has proven very helpful in the years to come. The booth that the owner had selected was a “down draft booth” in lieu of an “up draft booth.” I learned that the intake air came in through the ceiling of the booths after passing through a set of filters in the ceilings. The air passed through the booth downward into an exhaust tunnel that was to be constructed by forming a pit with concrete that routed the air to the edge of the booth where a fan and filter box would pull the air up from underneath the booth, through a series of filters, and into exhaust ductwork that would take the air out of the building. In this booth, that meant I would need to protect the booth itself – which was 20 ft x 30 ft – the paint mixing room, the tunnel under the booth through the filter box and on the discharge side of the exhaust fan until the air terminated the building through the wall or ceiling.
The first challenge I faced was with the entire 20 ft x 30 ft ceiling space being essentially a large duct plenum that was 18 inches deep. My options were to install the piping on top of the booth with drop pendants penetrating through both the top and the bottom of the plenum space, install the piping inside the duct plenum (therefore eliminating penetration through the top side of the plenum) or install the piping exposed in the room. In working with the owner, we determined that installing piping in the plenum space would work as there were large banks of removable filter boxes that would prove to provide access to installing the piping after the booth was erected. The next challenge we faced was sprinkler placement. With such large filter boxes taking up about 25 percent of the ceiling space, and the abundance of lights placed pretty much everywhere else in the ceiling, finding spots to install pendent sprinklers was extremely difficult, especially with the 100-ft2 maximum spacing requirement. Due to these issues, the booth itself had eight sprinklers! Another thing we needed to determine was where this intake air was coming from, after reminding myself of the section I read about protecting the sprinklers from freezing conditions. On this project, we determined that they were simply taking air from the plant and we shouldn’t have concerns with cold air presenting us with a freezing scenario.
Next, we moved on to protecting the tunnel under the booth. At the time, to be honest, it seemed a bit ridiculous to be installing sprinklers in a cement tunnel under the booth, but it did at least make sense due the nature of the use of the booth. The tunnel under the booth was 24-in. wide in the shape of an L headed to the corner of the booth where the exhaust fan was. The overall length of the tunnel was about 40-ft long before it terminated under the filter box. Getting piping into this tunnel proved to be another challenge, as we determined we would need to penetrate the side of the booth’s HVAC equipment near the filter box to get piping into the tunnel in order to install our sprinklers there. By that time, we were done figuring what needed to be in the pit and up to the filter box. We ended up with four more sprinklers in the tunnel and one sprinkler at the top of the filter box.
Next, we needed to cover the remaining ductwork that routed the exhaust air out of the building, as this wasn’t shown anywhere on the drawings. Another call to the GC resulted in a call to the HVAC contractor they were working with. The ductwork on this project was to go up to the deck above, which was about 20-ft tall and offset out the adjacent wall about 10-ft away. From looking back to Section 22.214.171.124, I determined at least three sprinklers would be required due to the minimum spacing requirement of 12 feet between sprinklers. I also discussed access to these sprinklers with the HVAC contractor, to which I was told, “He had never heard of such a thing” followed very closely by “Who’s paying for that, not me I hope?!”. We also discussed that there was a potential for this ductwork to be cold, so we determined dry sprinklers would be best in this area. In all, we had eight sprinklers in the booth: two sprinklers in the paint mixing room, five sprinklers in the tunnel, and three dry sprinklers in the exhaust duct – with a grand total of 18 sprinklers for a 600 ft2 room. With some quick math, we determined that each sprinkler was going to discharge at least 30 gpm with a grand total of at least 540 gpm without hose demand. This tiny little paint booth was getting a little out of hand, if you ask me!
After all of this, we priced up the work the way I originally determined. We had good water supply in the area, a 6-in. main into the building, a close feed main to tie into, and we still easily ended up in the five-digit price range for a very small room. Before I did my research, I thought it was as simple as slapping some sprinklers in a booth. I was thinking the maximum needed would have been six fed from an overhead system, a couple of days of service work, and easy money! I’m very glad I didn’t learn a very expensive lesson on that project and did the extra code research that day before sending a price out the door. After some sticker shock, the owner moved forward with the project and we learned just what protecting a paint booth took and could turn into on just a small booth like this. Since then, we have determined that booths seem to never be alike in one way or another, whether it be in the size of it, lighting obstructions, filter placement, direction of air flow, owner-preferred piping locations, etc. In what we learned from this small project, we were better able to prepare ourselves for other projects over the years, which lead us to protecting very large- and industrial-sized paint booth set-ups with several system types and arrangements including wet, dry, deluge, and foam – several of which required fire pumps just to supply them.
One last thing I want to mention – even though I am a new member on the NFPA 33 committee, I still don’t know it all when it comes to paint booths and we are always learning on every one we protect. There is limited information available on properly protecting them, so our recommendation is to always consult the Authority Having Jurisdiction (AHJ) for the projects you are proposing to see what they will require of you. But, hopefully, some of our lessons learned and code references will help properly prepare you for those conversations. After years of doing these, I am much more confident that the way were are proposing and installing these systems is the right way to do them – with submitting to many authorities over the years. Hopefully this article will help someone out there feel more comfortable with what they are proposing.
ABOUT THE AUTHOR: Jared Van Gammeren is the fire protection director at Midwestern Mechanical Inc. He has been in the fire sprinkler industry over 15 years. Van Gammeren holds a NICET Level III certification in Water-Based Systems Layout and a NICET Level III certification in Inspections and Testing of Water-Based Systems. He is the Registered Managing Employee in Iowa, Minnesota, and Nebraska; is an NFPA 33 committee member; and a volunteer fire fighter for his home town fire department in Inwood, Iowa. Van Gammeren’s professional training consists of courses of fire pump applications, inspection and testing, hydraulic calculation, and analysis & design of fire sprinkler offered by the Oklahoma State University, and the University of Wisconsin.
IMPORTANT NOTICE: The article and its content is not a Formal Interpretation issued pursuant to NFPA Regulations. Any opinion expressed is the personal opinion of the author and presenter and does not necessarily present the official position of the NFPA and its Technical Committee.