To agree with Thom and NFPA 33 I’ll drone on. As NFPA 33 states, shutdown the ventilation if the listing for the suppression system requires it. The total flood dry chemical systems do. The powder is light and would otherwise get sucked against the downstream filter. (As one of those normal issues when multiple trades are involved this is a common reason for failure of inspection of this type of system.) Simplified design is for 100 lf of air x cross section of booth. So I follow the listing. NFPA 33 is in accordance with the listing.
Sprinklered booth. It may be EH2, but this is one time all the heads in the design area are going to operate. This is what fire experience shows. Unless the just below the roof level is loaded, and fails to operate. Consider the question of whether the ventilation is a good thing, as it removes the products of combustion, vs the ventilation provides a continuous stream of fresh oxygen to the fire. The goal of most life safety features in a building are intended to allow people to escape to safety. The fire gases are the direct threat. The are hot, choking, poisonous, and vision impairing, by three modes. And the quantity of fire gases increase rapidly, and the rate of increase increases, in a tilted stepwise manner. We’ve controlled the rapid expansion of the fire with sprinklers. And the air outside the booth will not be what FF’s call hot. Sprinklers again. But it would still be smokey. How do we decide. Fire experience. We know that sprinklers with a couple exceptions are effective at keeping the fire in the booth.* The failure modes have nothing to do with ventilation. Again, as a flammable liquid fire, and maybe a car fire, were not extinguishing the fire. We’re confining and cooling it while it burns out. So we know from fire experience that ventilation doesn’t often cause fire to leave the booth. And we know that it makes escape easier and safer. It makes a safer environment for the FF’s. Plus there is the business continuity benefit. While the booth is out of service, and may or may not be headed to the recyclers, the rest of the operation should be back in operation next shift. Smoke has not damaged everything in the business. So we leave the fan on. Pro-point bonus for any lurking fire inspectors. When I first started doing booth inspections I didn’t have anyone teach me. So I had to study extra, and read the plans in detail. So the first time I got a ladder to go across the top of the booth to look at the motor and fan installation the installers blew up in anger. What I learned from the installers was that Grainger fouled up and sent out the next size smaller motor. What I found the next six months was that some how the foul ups were always for a smaller, never larger motor. Eventually word got out and this stopped. So just because the plans say 2 1/2 HP, it doesn’t mean the installed motor isn’t a 2 HP. You’ve got to look. And AFSA moderator, I’m not maligning by name a supplier. Of course Grainger sent exactly the motor that booth installers ordered and paid for. Bruce Verhei *Exceptions. Booths are required to have clear space around them; this may be reduced if adjacent to non-combustible construction. I admit this as theoretical, without personal knowledge. I have found cardboard etc stacked against booths. I haven’t seen a fire in this situation. The outside of the booth can be hot though. Roof penetrations through a combustible membrane. These are always tough to get right initially. And there is no fire inspection for reroof. And the one head most likely to be loaded is the dry head below the roof. But I’ve only seen this in an industrial situation, with near continuous spray, through three shifts. And the FF’s rapidly put those fires at the roof out. A plant in a small town with six volunteers responding in the daytime? I don’t know. Then fire extending directly from the booth fire. While considering proposing a code change years ago an FM engineer kindly provided me with a series of reports on booth fires from their covered properties. All the heads operated, all the time. The ones with fire extending out and operating large numbers of heads (up to 55) had in common bulk supply from outside the booth. All the fuel was pumped into the booth. > On Jan 12, 2018, at 10:29, Larry Keeping <[email protected]> wrote: > > I just took a look at what NFPA 33 says about fire protection and ventilation: > > 9.2 Ventilation Systems. Air make-up systems and spray area exhaust systems > shall remain functioning during any fire condition. > > 9.2.1* Where air exhausted from spray areas is recirculated, an interlock > shall shut down the recirculation of air during any fire condition unless it > can be demonstrated that shutdown creates a greater hazard. > > 9.2.2 Air make-up systems, spray area recirculation systems, and spray area > exhaust systems shall be permitted to be shut down and dampers shall be > permitted to close where the automatic fire protection system type requires > that ventilation be discontinued. > > Does that should answer the question? > > Larry Keeping > > > From: Sprinklerforum [mailto:[email protected]] > On Behalf Of Thom Heller > Sent: January-12-18 1:05 PM > To: [email protected] > Subject: RE: Exhaust Air - Paint Booth > > As an AHJ, in my jurisdiction, we would want the exhaust air to remain on > (removal of products of combustion in the event of a fire) while the make up > air would be discontinued. Thom > > From: Sprinklerforum [mailto:[email protected]] > On Behalf Of JD Gamble > Sent: Friday, January 12, 2018 9:41 AM > To: [email protected]; > [email protected] > Subject: Re: Exhaust Air - Paint Booth > > Bruce, > > Could you expand on “why” you would want the air to keep running? > > Get Outlook for iOS > From: Sprinklerforum <[email protected]> on > behalf of Bruce Verhei <[email protected]> > Sent: Friday, January 12, 2018 10:25:17 AM > To: [email protected] > Subject: Re: Exhaust Air - Paint Booth > > Are paint spray operations at this booth supplied by drum or IBC-quantity > containers located outside the booth? By that I mean as opposed to the more > common small containers on integral to the hand held spray gun or small > inline pot. > > It’s common to use a flow switch to drop power to pump connected to drum on > waterflow. > > Without this fire can attack hose in booth. Pump sees this pressure drop as > demand for product, and pumps remainder of drum or IBC (intermediate bulk > container) into booth. Result from a sprinkler design point of view can be > operation of dozens of heads outside booth. From occupants point of view > they’re now in a fast occurring, if not fast spreading, fire producing dark > smoke. I assume fully sprinklered building. > > I’d ask AHJ what they prefer. Total flood dry chem systems require fan shut > down. But sprinklers do not. But some AHJ’s might require fan shut down. From > a compliance point of view the AHJ and architect are trying to find a way not > to count the entire quantity of liquid as being in Use. > > As an Alternative Material and Method ruling design, the AHJ has considerable > sway. > > Two questions to resolve early are switch testing and retard setting. 5 > seconds seems to be adequate to prevent unwanted alarms in my experience. > > For the record I would have preferred to leave the fan running. But you > should call the fire plan reviewer for this project. > > Best. > > Bruce Verhei > > On Jan 12, 2018, at 08:20, Steve Leyton <[email protected]> wrote: > > I would say “probably” but a detection is faster and certainly more > conventional. I would actually defer to the electrician or EE who’s > overseeing design/installation of building controls and ask them. > > From: Sprinklerforum [mailto:[email protected]] > On Behalf Of JD Gamble > Sent: Friday, January 12, 2018 8:16 AM > To: [email protected] > Subject: Re: Exhaust Air - Paint Booth > > Sorry. Yes , spray booth. Flow switch specific to booth. > > Get Outlook for iOS > From: Sprinklerforum <[email protected]> on > behalf of Steve Leyton <[email protected]> > Sent: Friday, January 12, 2018 9:14:22 AM > To: [email protected] > Subject: RE: Exhaust Air - Paint Booth > > I assume you mean a spray booth? Is the flow switch peculiar to sprinklers > in the booth or will it signal upon flow of any sprinkler in the building in > which the booth is located? > > Steve L. > > From: Sprinklerforum [mailto:[email protected]] > On Behalf Of JD Gamble > Sent: Friday, January 12, 2018 8:12 AM > To: [email protected] > Subject: Exhaust Air - PaintBoith > > Quick question > > When using a flow switch to shunt trip a booth, should the exhaust air moment > be stopped as well? > > Get Outlook for iOS > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
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