View Full Version : Fire! Fire!

Bob Keyes
09-14-2007, 11:16 PM
Well, after a lot of engraving and cutting over the last 24 months I had my first fire tonight. I was cutting some 1/2" acrylic and was busy with something else at my bench adjacent to the engraver. :confused:

I heard a muffled pop and when I turned to look the inside of the engraver was aflame. I just turned off the laser beam and let the machine run. Then I grabbed my trusty, new I might add, First Alert Tundra fire extinguisher, opened the lid and sprayed the fire out. There was a brief secondary flare up which the Tundra took care of easily. :D

Dirty mirrors, dirty lens, warped top window, but no other damage. The cleanup was easy once everything cooled down. A paper towel or 3 and some Windex and it was over.

Two things here. I was right there with the machine. If I had not been it would have probably burned down my house.

Second, I had a fire extinguisher right there within reach. There is really no excuse for not having one. First Alert has these now for less than $20.00. If I had not had one I'm not sure what would have happened, but I am sure it would have cost me a whole lot more.

Heed the warning. I did and I'm sure glad. Go get the Tundra if you don't have an extinguisher already. :p

(Standard disclaimer. I don't work for nor have any affiliation with First Alert. They just make an effective, affordable fire extinguisher.)

Ken Fitzgerald
09-14-2007, 11:28 PM
Bob...I don't do lasers....but I do wood working. I will be buying a fire extinguisher and it will be mounted on the wall next to the walk thru door!

Thanks for posting!

Craig Hogarth
09-15-2007, 12:34 AM
Given a choice between burning down the house or using the tundra, I'd use the tundra. But dry chem extinguishers can destroy electronics beyond repair and a co2 is a much better option.

Mike Hood
09-15-2007, 9:44 AM
... and most fire extinguisher stores have used CO2 bottles you can get very inexpensively. I have a 30 pounder sitting next to mine and if that's not enough to stop a fire, it's time for 911. :)

CO2 won't hurt electronics or foul your optics like an abrasive dry chemical would.

pete hagan
09-15-2007, 9:44 AM
Bob, sorry to hear of your fire. I just scolded a 20 something for "goin to lunch" while cutting a sheet of 3/16 acrylic last week. I have printed your post and pasted it to his time card!

I'm buying a CO2 extinguisher first thing Monday. We've got several dry chems on the walls but I definately do not want to be cleaning the laser inerds from it.

Let me know if you need any assistance up here in horse country.


Gary Hair
09-15-2007, 12:05 PM
Forget dry chem and co2, you really want a halon extinguisher. They are about 5x as much as the others but you won't ruin your machine. I have two small ones I bought a few years ago and always have them within reach.


Bob Keyes
09-15-2007, 3:35 PM
Here's what I know about fire extinguishers. Halon would be the best. Very expensive, cannot be made in the US anymore, supply will slowly run out. CO2, fairly expensive. Need training to operate. Has to be refilled if used only once. Clean up is non existent and it won't hurt electronics although the potential is there since the ice it forms is electrically conductive. Dry chemical is bad. Effective fire suppressant but the clean up is really nasty.

The new Tundra is a liquid. Very quick, I found out, at snuffing out the flames. It comes in a can like spray paint and is used until it is gone. Then you throw it away. The clean up was easy as stated before. It is dirt cheap. I went on line and bought 4 of them for under $60.00.

Whatever you decide, GET SOMETHING!! NOW!

AL Ursich
09-15-2007, 10:11 PM
I have 2 fifteen pound CO2 bottles plus a few dry chemical and I see this as my first choice. Been around a few fires in my Navy days and have an appreciation for CO2.

A bag inside the can is pressurized and only fluid comes out of the can, not a bad design. No flammable gas...... Couldn't find anything as to weather it can stand freezing in a unheated shop? The Laser Shop is heated but the Wood Shop is not yet.

Thanks for the tip, I had not seen them before. Haylon is good but bad for the earth.....


Mike Hood
09-15-2007, 10:16 PM
I don't know where you guys keep getting this "dry ice is conductive" and therefore dangerous around electronics. That's just not true.

CO2 (in gaseous, liquid, or solid form) is non-conductive, non-toxic, chemically inert, and non-abrasive. I wouldn't think twice about using it on my laser. It's inexpensive and can deliver a steady stream of fire extinguishing agent to the laser and the exhaust system.

Get a 20# bottle and keep it handy. If you use it, you only need to get it refilled and it's incredibly inexpensive to top one off.

AL Ursich
09-15-2007, 10:32 PM
I believe from my Navy Fire Training days that it is the water vapor in the air that forms the ice on the outside of the horn that is conductive. Water Vapor ice not dry ice.

Carbon Dioxide (CO2) extinguishers are most effective on Class B and C (liquids and electrical) fires. Since the gas disperses quickly, these extinguishers are only effective from 3 to 8 feet. The carbon dioxide is stored as a compressed liquid in the extinguisher; as it expands, it cools the surrounding air. The cooling will often cause ice to form around the “horn” where the gas is expelled from the extinguisher. Since the fire could re-ignite, continue to apply the agent even after the fire appears to be out.

I have also seen guys get a nasty static electricity shocks from holding the bottle while discharging it. They recommend setting it on the ground while discharging it. Only happens under very dry conditions and sometimes standing on a steel deck.


USN Retired

Craig Hogarth
09-15-2007, 10:53 PM
I don't know where you guys keep getting this "dry ice is conductive" and therefore dangerous around electronics. That's just not true.

I think everyone is talking about condensation and freezing from the expended CO2.

But with any electrical fire, the first thing that needs to be done is to shut off power, preferably at the source. This will reduce the chances of reflash and no amount of water will damage the equipment.

AL Ursich
09-15-2007, 11:19 PM
NORFOLK, Va. - A small fire broke out aboard a Navy guided missile cruiser Saturday, injuring five civilian workers, officials said.
The workers were taken to Sentara Norfolk General Hospital. The extent of their injuries was not immediately known.
The USS Leyte Gulf was undergoing repairs and a renovation when the fire started Saturday morning, Norfolk Fire and Rescue Battalion Chief Bruce Evans said. The blaze was put out by a portable extinguisher about 15 minutes after it began.
The fire was caused by an accidental build up of lacquer thinner fumes, Evans said. The source of the ignition was not determined, he said.

The ship, a Ticonderoga-class cruiser, was docked at BAE Systems Ship Repair Systems. The fire occurred two decks below the main deck, Evans said. No Navy personnel were injured, he said.
A message left by The Associated Press at Naval Station Norfolk was not returned.
The 567-foot warship carries two SH-60 Sea Hawk helicopters and its armaments include Tomahawk missiles, torpedoes and Harpoon missile launchers.
Leyte Gulf is based in Norfolk and carries a crew of more than 380 officers and enlisted personnel.

Joni Campbell
09-16-2007, 8:37 AM
Oh No I am glad you got it put out before you had any real damage. I'm off to get a CO2 just to be safe :)

Darren Null
09-16-2007, 8:57 AM
Obvious, I know, but in an emergency you're not always thinking about anything but the fire. Power off first, yes.

Also with CO2 your hand can freeze to the horn, so pull your sleeve down or wrap something round it first...you don't always have time to thaw naturally and you can rip a fair amount of skin off if you're in a hurry.

Also, consider ventilation. CO2 and Halon work by starving the fire of oxygen; and it can have the same effect on you if you're not careful/in a poorly ventilated or enclosed space/are very enthusiastic putting the fire out.

I have a large CO2 extinguisher and a small Halon one (illegal in the UK, but I'd like to see somebody prove that there's an inert gas in all that smoke I'm letting out the window).

EDIT: I'm also glad that you got off with no damage Bob. Good one.

Mike Hood
09-16-2007, 9:14 AM
The thing about CO2 is you can dispense a much larger amount of agent at a much lower cost. A used CO2 unit can be picked up very inexpensively and a 20 lb unit will put out a HUGE fire if used properly.

You can always regulate the amount of CO2 you're dispensing and once the cabinet is full of CO2... nothings gonna be burning. Same goes for you exhaust system.

Bob Keyes
09-16-2007, 2:07 PM
My message was intended to be GET SOMETHING !!! All mentioned extinguishers are effective. Look at each and decide what is best for your budget, but GET SOMETHING !!!

Frank Tralongo
09-16-2007, 11:02 PM
Hi guys,
There is one other problem that seems to have been missed Thermal Shock.
Co2 is so cold that it MAY cause warmed or hot components (IC's/computer chips/transistors/etc.) to fail when sprayed on them.
Laser running for a period of time, fire breaks out, you turn POWER OFF, and spray co2 to put fire out. You hit some of the circuit boards within and you may or may not have caused a permanent component thermal failure.
Halon is still the best for component electronics even though it costs a ton of bucks and is not so good for the ozone.
BTW there is a second generation Halon that is safer and is about 2.5 times higher than Halon.

Mike Hood
09-16-2007, 11:58 PM
Well... that's a stretch... but I suppose if your laser is one FIRE, and your biggest worry is getting it too cold... :)

CO2 extinguishers don't spray dry ice, but they do rob a fire of both the oxygen and heat needed to sustain combustion. I think the righ emphasis should be to get something and a lesson to all of us that we are playing with fire with our toys.

Frank Tralongo
09-17-2007, 3:09 PM
Geez and all I wanted to do was share some factual information...

I worked in the computer industry for over 35 years and when designing systems rooms this was a major consideration for fire fighting. When Halon was being introduce one of its major benefits was not inducing thermal shock, the other was for humans to be in the room and not be impacted when the fire systems were activated.
Any compressed gas when expanding removes heat and can actually exceed the thermal specs of various circuit devices. Co2 happens to be one of the gases that gets very cold when expanding.

BTW if you put a canvas sack on the horn and shoot a co2 bottle into it it will in fact make dry ice.....
"Believe it or not"

Joe Pelonio
09-17-2007, 3:57 PM

Besides the educational controversy over the best extinguisher, I'd be interested in knowing what was burning and why. Was it the acrylic itself on fire? I did another review of my laser and the only thing that could burn is the material, drive belts, and electronic boards/cables under the beam cover, the rest is all metal. The only flaring I've seen on acrylic is when it's cutting really close to the material edge, which I attributed to it getting a lot more air, from both sides of the cut, but even then it's never caught the material on fire, just a bit of flame moving with the beam, and adding more air assist ends that.

Bob Keyes
09-17-2007, 7:19 PM

It was the acrylic itself. It was 1/2" and I was cutting at 100 power and 2 speed. Apparently some of it melted and caught fire underneath the vector table. That, in turn, flared up and set the edge of the sheet on fire, which melted, etc. etc. etc.

I was using full air assist at the time. Not exactly sure what happened, but it sure was on fire when I turned around.

Kim Vellore
09-17-2007, 7:58 PM
I have used CO2 fire extinguishers to put out flames in the open during a ERT training and considering the volume inside the Laser you don't need much to replace the air with CO2, for that little volume you will not be producing enough dry ice to have any detrimental effect. I am assuming the CO2 you will be using is a one with a trigger and does not dump it all with no ON/OFF control. If you have to put so much CO2 to extinguish the fire that it causes problems with dry ice then I would think the fire would have caused much greater damage.


Joe Pelonio
09-18-2007, 5:18 PM

It was the acrylic itself. It was 1/2" and I was cutting at 100 power and 2 speed. Apparently some of it melted and caught fire underneath the vector table. That, in turn, flared up and set the edge of the sheet on fire, which melted, etc. etc. etc.

I was using full air assist at the time. Not exactly sure what happened, but it sure was on fire when I turned around.
Perhaps another lesson then is that on full power and a very slow speed one should stand there and watch it. Those are nearly the settings I use for my 45 watt (100/3) to cut 3/8" acrylic and while I don't do it often, next time I'll keep a close eye on it.

Ricky Gore
11-13-2007, 11:07 PM
Just wanted to mention that I found a guy on eBay selling Tundra for 5 bucks a can. I bought 5. I have nothing to do with this guy, I am just passing along info! It's on eBay item number 300171556965

I hope I'm not in violation of any rules by posting this. If I am please accept my apology and remove this post.


Kim Vellore
11-13-2007, 11:45 PM
Maybe it is expired, do you know when is the expiry date. I am waiting for the seller to respond