How to Clean Spray Booth Exhaust Stacks

Finishers discuss whether it's worth the effort to clean the exhaust vent stack for a spray booth. April 18, 2010

We are in a building with approxmately a 25 ft roof and we have an exhaust stack that run from the back of the spray booth all the way to about five or six feet above the roof level.

We have always cleaned behind the filters, and also climbed on top of the booth and gone through the access door to clean around the fan but there is about 15 feet of stack above that where have never really cleaned. We recently borrowed a scissor lift to gain access to the roof. Once on the roof you can't even see down into the stack without standing on a ladder. So we screwed a wire brush to a long 1x4 and we've been sticking it down in the stack trying to scrape off the excess lacquer but it is just not working very well.

Is this a problem that I should even be worrying about? If so, does anyone have this same problem and how do you go about cleaning? Even if the wire brush worked well, it is almost impossible to reach all the way down to where we need to get.

Forum Responses
(Finishing Forum)
From contributor G:
"For this a problem that I should even be worrying about?" No. Build-up on the fan blades is more of a concern. That could cause off balance, bearing wrecking wobble. If you're really concerned about dust build-up in the stack, try a long air lance connected to the high pressure air.

From contributor H:
As long as you have a sprinkler head above the fan you should be fine. The real issue is to get more efficient booth filters. I used to use the cheap glass ones. Now I use polyester filters They don't itch, they last longer, and there is less dust behind the filter box.

From contributor F:

I beg to differ on the "should I worry about it" response of no. If it is truly a nitrocellulose lacquer overspray, they are extremely flammable. Of course, a flame source is needed but not much. I would take the time to clean them if it where me.

From contributor J:
I have nearly the same configuration with my booth stack. I could find no course of action other than what has been stated by contributor G and H. Take care of the blade and your filtering, and install fire suppression by either powder or water sprinkler inside the stack, which is required by NFPA standard by the way. This is the best you can do unless you're prepared to take your stack apart.

From contributor F:
How often to clean? Good question. What really needs to be addressed is; why is there so much build up of overspray? Filters need to be changed more often. Although I have never experienced a fire in the exhaust stacks. I have been involved in three plant fires back in the 1980's all involving lacquer over spray. Just a little concern on my side.

From the original questioner:
Thanks everyone for your time. We do have a sprinkler inside the stack. Contributor F - you recommending taking the time to clean the stack. I tend to agree, which is I why I posted this. How should I go about accessing the inside of the stack? From the ground reaching up, I can only go so high and from the roof reaching down I can only go so low. There is at least a ten foot section I cannot reach. Is it even something to worry about? If so what should I do?

I believe before I started with this company they were using fiberglass filters which, in my opinion, let a lot more dust through. As far as I know the stack has never been cleaned. I will try out the long air lance - good advice.

From contributor G:
I have seen finishers who, under production pressure, skipped the regular booth maintenance when the filters got plugged, and just pull a section away from the channels to there was better suction in the booth. All the wet overspray went up the stack. I've no doubt some of it stuck to the inside of the piping. Also, I've seen guys remove a section of filter so they could blow all the dried overspray from the walls and floor of the booth up the stack, onto the roof and over the cars in the parking lot.