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Opening the Door on Spraybooths

When Mark Clark’s PBE career began back in the Stone Age of the 1970s, fewer “officials” were involved in building a compliant spraybooth.


Mark R. Clark is owner of Professional PBE Systems in Waterloo, Iowa. He’s a popular industry speaker and consultant and is celebrating his 32nd year as a contributing editor to BodyShop Business.

Enclosing the spraying of flammable material inside a fireproof box is the impetus for automotive spraybooths. Various regulatory agencies, led by fire code enforcement, call for containing any combustion inside a corral that won’t readily burn, and metal sheeting, cement blocks and thick sheetrock all qualify.

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When my PBE career began back in the Stone Age of the 1970s, fewer officials were involved in building a compliant spraybooth. These days, as many shops can attest, the electrical, building, environmental, safety and fire inspectors all have something to say about what’s legal in your area.

My First Sale
The first spraybooth I recall selling was a cross-draft DeVilbiss – your basic hip-roof (so the lights pointed toward the car), 14-foot-wide by 24-foot-long by 9-foot-high metal box. There was no air replacement unit, so when the fan kicked on, it sucked all the air and heat out of the main shop and slammed shop doors like explosions.
The purchasing shop was forced into buying the booth to get the city to issue it an occupancy permit and was borrowing big to cover the $3,500 cost. We decided we could save money and assemble the box ourselves pretty easily – no deep exhaust pit in the floor, and no specific height for the exhaust stack out the roof (so we went right out the back of the shop wall.) We only hired out the electrical wiring.


The shop’s techs volunteered to help, and in two nights (and five cases of beer), we bolted together most of a legal spraybooth. The hardest part was getting the filtered door assembly to hang square in the big, wobbly doorway. We finally succeeded, loaded the filters and started painting cars.

Filter Folly
Installing filters in a spraybooth was a thankless task back in the day, and it still is today. But, since moving air always takes the path of least resistance, any gap around the filter and its mounting hole will cause huge amounts of air to bypass it and rush into the booth uncleaned. Whether cardboard-framed, heat-sealed and wire framed, or rolls of bulk media, intake filters have to fill their mounting holes perfectly or shocking amounts of dirty air can blast into the booth cabin.


That original DeVilbiss booth’s filtered doors each held six 20-by-25 intake filters. Taking plenty of time to seat all 48 edges squarely and cover any possible gaps with masking tape made a huge difference in clean paint work.

The first thing to wear out in that booth was the folded rubber seal (like an inner tube) along the bottom of the door, where it dragged along the floor. The moment it wore through, dirt whooshed under the door instead of getting sucked through the filters. The vibrating exhaust fan shook the metal walls every time it ran, and pretty soon, the dirty air was leaking in along the seams of the panels, too. You could see the smudge tracks on the white walls. Even today’s double-walled, insulated, top quality booths need to be squared up, caulked up, tuned up and cleaned out on a regular basis.

Door Debacle
Time passed, and I actually sold some spraybooths to shops that weren’t responding to local fire regulations but wanted to achieve cleaner paint work. Even back when the door rate was $20 an hour, keeping the dirt out of the paint made production flow much faster.  


Many of my customers in small town Iowa wanted to build their own spraybooths to meet local fire codes. In most towns, cement block construction met the flame containment rating, as did double layer 5/8-inch sheet rock.

Both DeVilbiss and Binks offered a filtered door assembly that you could affix to any compliant sidewalls, and I sold several to do-it-yourself customers. My recollection is that the door kit shipped to the Midwest for about $1,200 shop cost.
I had one farm town shop that refused to spend that kind of money for some doors. The owner located his project in the rear corner of a cinderblock building so he would have two booth walls already in place. He laid a block wall down the third side and started building his doors.


I’m no contractor, but it seemed to me a spraybooth door made of two big sheets of 5/8-inch sheetrock screwed to metal two-by-fours would be kind of heavy. Even with the two (two!) filter holes he cut in each door, they weighed a ton.

I wasn’t there to see the door construction, but I was on hand for the mounting circus. He and three techs wrestled the doors into place, used some hardware store hinges to screw them into the walls and stepped back to admire their work. The painter went to reopen them and, as he pulled them back, both tore free of the hinges, crashed to the ground and broke apart. His $1,200 factory door kit arrived within the week.  


A Common Mistake
The shop also made the common mistake of thinking that less filtered area would make for less dirt in the paint. The exact opposite is true. You can’t have too much filtered area. The exhaust fan in an average spraybooth will constantly pull about 10,000 cubic feet of air every minute. If there is insufficient filtered air available, the fan will drag air from every crack, gap and pinhole in the cabin.

In a cross-draft booth, I’m a big fan of pleated filters for the intake air. In the same 20-by-25 opening, you can have four or five times that in filtered area. On the subject of filter media, remember that what makes any downdraft spraybooth perform well is the sophisticated, $1,000-plus, air-balancing filter pad set. Through the magic of physics, these filters won’t pass air though them until the pressure across the face of the filter is even, ensuring smooth air flow throughout the cabin – a heck of a neat trick! A $300 filter set might fit the holes, but won’t do the same thing.


An Ounce of Prevention
Whatever style of fireproof box your shop is using to paint cars, take plenty of time to load and secure the best quality filters you can buy. At $45 per labor hour, every minute the painter spends removing dirt and trash from the paint work costs the shop $0.75. An ounce of prevention is worth a pound of cure.

Mark R. Clark is the owner of Professional PBE Systems in Waterloo, Iowa; he is a well-known industry speaker and consultant. He is celebrating his 25th year as a contributing editor to BodyShop Business.

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