Fire Extinguisher

[Jim Priest]

I've been reading some posts here on fires and flare-ups and ran across the post of the crispy Epilog. That got my attention...The big takeaways are "DON'T LEAVE THE MACHINE UNATTENDED" and get a good fire extinguisher. Extinguishers are a complicated topic in their own right, so I'm looking to the experienced members for a recommendation. Thanks in advance.

[Gary Hair]

Halon, or the halon replacement, would be best for the laser as they don't have any corrosives to cause damage. A CO2 extinguisher will pretty much ruin your laser even though you put out the fire.

[Robert Walters]

A CO2 extinguisher will pretty much ruin your laser even though you put out the fire.


Gary,

Why do you say a CO2 extinguisher will damage a laser?

Could you be confusing it with a common dry chemical one?

[Ronald Erickson]

I was just going to say the same thing. A CO2 extinguisher is just carbon dioxide. It wouldn't be good for putting out lighter materials as it would blow them around due to the gas pressure, but it wouldn't damage a laser. A Monoammonium phosphate (ABC Dry Chemical) extinguisher would not be good for a laser however as it is caustic and is designed to melt to smother a class A fire.

[Glen Monaghan]

A simple spray bottle with misting nozzle, filled with plain water, is quite sufficient, effective, convenient, and inexpensive for the vast majority of flareups and fires in a laser engraver (if caught while still small, before it has begun to engulf the machine). However, a full-fledged fire extinguisher is also a must nearby for when the spray bottle is inadequate.

Like Robert, I think Gary is confusing a CO2 extinguisher with a chemical extinguisher. The chemicals are often corrosive, and they create a mess that is difficult to clean from nooks, crannies, and electronics. The worst possibility when applying a CO2 extinguisher to a laser machine might be a cracked piece of glass (tube, lens, or mirrors) or broken electronic board - potential for breakage due to the thermal shock and stress caused by going from being exposed to the heat of fire to freezing temps of the expanding CO2.

[Tim Bateson]

A simple spray bottle with misting nozzle, filled with plain water, is quite sufficient, effective, convenient, and inexpensive for the vast majority of flareups and fires in a laser engraver (if caught while still small, before it has begun to engulf the machine). However, a full-fledged fire extinguisher is also a must nearby for when the spray bottle is inadequate. ...

I agree with Glen about a spray bottle. A flare-up is easy to put out with a spray bottle. If however you have a full on fire that requires an extinguisher, than any damage that extinguisher causes is the least of your worries.

[Gary Hair]

Could you be confusing it with a common dry chemical one?

Yes, you are (all) absolutely right...

[Robert Walters]

NOTICE: I'm not an expert nor even have a clue, use this info at your own risk, your mileage may vary, you and others might die, you might burn down everything, and you might have a very bad day. SEEK A PROFESSIONAL prior to even considering anything you read here. This is basically a "readers digest" version to help people understand the basics and do their own through research.


FIRE TRIANGLE

There are three things needed to have fire:
1. Fuel (paper, wood, gasoline, etc)
2. Oxygen
3. Heat

If you remove or don't have enough of any one of those, no more fire.

http://en.wikipedia.org/wiki/Fire_triangle


What fire extinguishers do is basically remove or reduce the effectiveness of one or more of those elements.


CLASS OF FIRES (Based upon United States "standards", may differ in other regions)

There are basically four classes of fires:

CLASS A: wood, paper, cloth, cotton, etc. Typically produce a white smoke.
CLASS B: oil, grease, plastics, rubber, petroleum products, etc. Typically produce a black smoke.
CLASS C: Any combination of the above and electricity is involved. If electricity is removed, reverts back to it's A/B equiv.
CLASS D: Explosives, specialized metals (magnesium), and other exotic things.

http://en.wikipedia.org/wiki/Fire_classes


The most common (80% or more of the time) fire extinguisher you will see for home and office use is DRY CHEMICAL (or dry powder). Another is CO2 (maybe 15% if that), usually it will have some type of "tube" or "funnel" two inch in diameter or greater on the dispenser end. Then there are more specialty types (rarely seen, maybe 5%) like Halon (banned) or one of it's replacements (FM200).


Fire extinguishers need to be checked at least once a year at the very minimum. Dry chemical can begin to "cake up" over time or lose their pressure. Ironically you might find an expiration date on the box but not on the extinguisher itself, so write the expiration on the extinguisher or at least the date of purchase for your own records. *I* feel disposable extinguishers should be replaced every five years. They are cheap enough, and you can donate your old ones to volunteer fire depts to give demonstrations of fire extinguisher usage, or show your kids how to use one properly.


Here is a $20 Fire Extinguisher
http://www.homedepot.com/p/Kidde-1-A-10-B-C-Recreation-Fire-Extinguisher-466142/100015934?N=5yc1vZbmgpZ1z10q66Z1z10z5j


1. It's DRY POWDER
One drawback about dry powder is the chemicals used are corrosive if not cleaned up quickly and the powder gets EVERYWHERE!

2. It's rated for: 1-A:10-B:C

Ok, let me try to break down this rating the best I can...

The "A" and the "B:C" represent the classes (types) of fires it's effective on.
The numbers are how effective it is on that particular class of fire (higher the number, the more effective).

Quoting http://en.wikipedia.org/wiki/Fire_extinguisher#United_States

"Fire extinguishing capacity is rated in accordance with ANSI/UL 711: Rating and Fire Testing of Fire Extinguishers. The ratings are described using numbers preceding the class letter, such as 1-A:10-B:C. The number preceding the A multiplied by 1.25 gives the equivalent extinguishing capability in gallons of water. The number preceding the B indicates the size of fire in square feet that an ordinary user should be able to extinguish. There is no additional rating for class C, as it only indicates that the extinguishing agent will not conduct electricity, and an extinguisher will never have a rating of just C."


So the "1-A" means that particular fire extinguisher putting out a paper or wood fire would be the same as dumping 1.25 gallons of water on it. Which really isn't all that good to be honest. I say that because not all of that water is going to land directly on what is burning. Some of the water initially is going to be converted to steam, and if the material that is burning is thick or dense, there can be hot embers inside where water isn't gong to penetrate all that well. If those embers are not put out well enough, could cause re-ignition sometimes even 20 minutes or more later on.


The "10-B:C" means it can be used on a Class B or C fire that is 10 square feet (3ft by 3ft) or less by an ordinary user.
Well, that can be subjective to an extent. If the heat from the fire is too great for you to get close enough to it, it may not be as effective as you want it to be.

If you look at the range of that extinguisher, it says "six feet". Which pretty much means you need to be standing very close to it, and if this is outdoors (dumpster or trash can fire as example), there may be wind blowing flames or smoke in your direction making you stand further back than the effective range.


One reason to use a CO2 Extinguisher around a laser or other high end electronics, is that it's just CO2. the same stuff dry ice is made from and the same stuff that gives soda bubbles. It gets EXTREMELY COLD when dispensed, non-conductive (safe around electricity), and the only real effects that remain is the condensation it leaves behind, much like leaving a cold soda can out in the sun and the droplets of water form on the outside of the can.


When I say EXTREMELY COLD, I mean it. It can cause the user to have frost bite. It's highly recommended to have and use proper (ANSI Approved) protective gear (face shield, gloves, etc) when using one, as they can even leak backwards towards the user when operated. Also good for chilling beer in 60 seconds or less =)


You can also check boat/marine supply houses for various types of fire extinguishers.
Here is a "halon alternative" which they say is more effective than CO2 is:

http://www.westmarine.com/kidde/kidde--halotron-i-fire-extinguisher-systems--P001219419

Note the price for a 1A-10B:C rated fire extinguisher has jumped from $20 to $370, but the range has change from 6 feet to 9-15 feet too. Just like our lasers, every thing is an option, so don't forget to buy the mounting bracket if one is not included.


ONE MAJOR IMPORTANT FACTOR

to consider for use around a laser engraver is that we have blower/dust collectors that are pumping in air (oxygen) to the fire at an obscene rate; basically fanning the fire BIG TIME. They are also sucking out the dry chemical or CO2 that we need on the fire to extinguish it, essentially reducing the extinguishers overall effectiveness dramatically.

You MUST have a way to shut off airflow in case of fire (that includes air-assist), usually this is a "blast gate". Some of them have a built-in switch which is wired to the blower/dust collector to turn it on/off at the same time. Realize that if you just "turn off" your blower, it takes time for the airflow to stop, and why I mention a blast gate as it will be instant.


Some extinguishers don't even have a "Class A" rating at all.
Some be sure to check the labeling.


NEVER block the access to an extinguisher by placing boxes or furniture in it's path.
Basically someone in a wheelchair should be able to grab the extinguisher if needed.


Don't go for those "gizmo" extinguishers you might come across "AS SEEN ON TV" unless there is a specific rating on them. They may or may not live up to their claims, but that UL (Underwriters Laboratory) Rating is there for a reason; it has been tested to meet a certain level of guidelines.


There are specialty requirements for aircraft (FAA) and marine (United States Coast Guard), as well as some for transport of certain items on highways (DOT) for extinguishers as well.


Another thing to consider is the re-ignition (re-start of the fire) if you don't have the right rating, size, type, or proper use of an extinguisher.


I hope this at least helps someone to "understand" a little more about fire and fire extinguishers at least.