The ubiquitous dry chemical fire extinguisher is cheap, suitable for multiple fire types, and UL listed, but it has some serious shortcomings. The typical 5BC extinguisher is often spent in as little as 10 seconds; it’s easy for an inexperienced user to deplete one in a panic, before the fire is out. The resulting cloud of chemical particles is highly irritating, which makes reentering the space to confirm the fire is out impractical in many cases. Finally, the chemical itself, most commonly mono ammonium phosphate, is highly corrosive to electronics, often ruining equipment. HFC 227 (formerly Halon) and C02 extinguishers are safe around electronics, but are expensive and have limitations of their own. A new generation of fire extinguishers, resembling a fat flare in appearance and function, promise to solve most of these problems … but do they? We were all schooled on the fire triangle. Heat, fuel, and oxygen. Remove any leg and the fire dies. Water cools by evaporation. CO2 suffocates. Dry chemical removes fuel by coating it with ammonium phosphate particles. Since then, fire extinguishing theory has evolved into a fire tetrahedron, adding chain reaction to the group. Pyrotechnically generated aerosol fire suppressants (PGA)—the generic name for these flare-style extinguishers—break the chain reactions that sustain a fire by chemically neutralizing reactive intermediates with a cloud of potassium particles. These are formed in a flame, along with other inert byproducts.
These newer extinguishers have several positives:
- Longer Discharge Time. 12 seconds for the tiny Maus and 50 seconds for the still compact Element.
- Less Residue. Reduced corrosion damage to electronics and minimal clean-up.
- No Reignition. So long as the cloud remains in place, relighting is prevented.
- Compact. Less than 1/3 the volume of 10BC dry chemical extinguisher.
- Rugged. Less prone to physical damage. No handle or gauge.
- Inexpensive. 1/3 to 1/5 the price of clean agent extinguishers (carbon dioxide or HFC-227).
There are also some negatives:
- Not UL listed. Because there is no US standard describing this new technology, they can’t be certified and do not satisfy requirements in NFPA, USCG, or DOT regulations. They are CE certified, and these standards cover many of the same requirements, including soundness of construction and extinguishing capacity. They are achieving market acceptance in the UK and Europe, but remain relatively unknown in the US.
- Health Risks. The manufacturers say “non-toxic,” but industry and scholarly papers are more cautious. The aerosol particles are very fine, on the order of 1-3 microns, and will penetrate deep into the lungs, causing unknown damage. Dry chemical particles are much larger and will make you cough, but have proven safe.
- Corrosion. There is a small amount of alkaline powder that can draw moisture and cause corrosion if left in place. Vacuum and blow it out, being cautious not to breathe the dust.
- Zero Visibility. Because of the small particle size, the cloud is very slow to settle, perhaps 20 minutes or more. This is good for preventing reignition, but bad for seeing what you are doing. Dry chemical settles much faster, within a few minutes.
- Can’t Turn It Off. Imagine yourself putting out a small electric fire in the cabin. You were finished in 4-6 seconds, but you can’t turn it off. The Maus and Firepal continue to burn for 12 seconds, and the Element burns for 50-60 seconds. How do you get rid of it? Open a porthole with one hand? Climb the companionway ladder in a smoke-filled cabin with a lit flare in one hand?
AUTOMATED FIRE EXTINGUISHERS FOR ENGINE ROOMS
|MANUFACTURER||KIDDIE||NORFIRE INC.||FIRE PAL||ELEMENT|
|MODEL||Mariner Rec5||Maus Xtin Klein||FP50||E50|
|DISCHARGE TIME||About 10-12 seconds||12||12 (not tested)||50 (not tested)|
|UL RATED||Yes||Nonfire Inc.||No||No|
|RATING||SBC||between 2BC and 5BC||between 2BC and 5BC||between 2BC and 5BC|
|DIMENTIONS||3.5" x 12"||2" x 9.4"||2" x 9.4"||1.2" x 11.75"|
We didn’t repeat the standard tests; these units have passed ISO muster with regard to sturdiness and rating. But we did have a few practical questions. To answer them, we built a small fire, limited in size as an incipient fire should be, including wood, fiberglass, gasoline, polyethylene, and PVC. After lighting, we gave it several minutes to get going, waiting until we saw burning fiberglass and dripping plastic. We then put it out with the Maus.
To use point it away from people, pull the safety ring, and press the yellow button. The yellow button activates a piezo lighter, like a barbecue lighter, which ignites the pyrotechnics that power the extinguisher. There was a “pop” as the rubber storage plug discharges from the nozzle and banged into the washtub, followed by a steady hissing and solid stream of extinguishing media for the next 12 seconds. The extinguisher becomes slightly warm, but not excessively so. It has been suggested they you could simple lob it into the engine room and close the door, and that seems reasonable since not even the nozzle becomes hot enough to start a fire, but don’t take that as an endorsement.
The mess is certainly far less than dry chemical, nearly non-existent. However, we noted minor corrosion of solder and brass coupons (in the test tub but away from the flames) that were coated with extinguisher residue and left in a humid jar in condensing condition for five days. The pH of the residue is rather high; 9-11 as measured by dampened pH papers in the test area and the corrosion coupon jar. Concerns have been voiced about long-term corrosion of electronics. We advise that you blow out the area and all equipment using compressed air, taking precautions to avoid breathing the dust (mask with HEPA filters).
The photos don’t do justice to the size and density of the cloud. After finishing our photography, we turned around and noticed that several acres downwind were quite foggy. Inside the cabin of a boat, or even in the cockpit, you can expect zero visibility to persist for some time, depending on ventilation. The fog is light does not settle out.
Unavoidably, we inhaled a small amount, even though we were in the open and upwind. There was slight bite in the air, characteristic of the alkali in the extinguishing media, but it was not choking. Investigators have expressed concern that the very fine nature of the aerosol will cause lung damage—it is much finer than dry chemicals. Pyrotechnically generated aerosol fire suppressants are universally not recommended for confined spaces; there have been fatalities when similar chemistry units discharged into confined spaces. We question claims that the gas is harmless and advise you to exit a confined space fast.
We included burning plastic and fiberglass to see if they would try to reignite. The fire was visibly out within 2-3 seconds, and when the Maus was finished, there was no glow or smoking of the embers.
AUTOMATED FIRE EXTINGUISHERS FOR ENGINE ROOMS
|MODEL||THIA Tube||TD Series|
|EXTINGUISHING MEDIA||MEDIA HFC-227||HFC-227|
|PRICE||$99 for 2 ft3 to $899 for 75ft3||$145 for 14ft3 to $280 for 55ft3|
Maus Xtin Klein. Remarkable for its diminutive size, this flashlight-sized fire extinguisher (9.4” x 2”) by Swedish company Nordfire packs a lot of extinguishing power into your palm. Roughly equivalent in extinguishing capacity to a much larger 5BC dry chemical extinguisher (CE 13B, which is falls between UL 2BC and UL 5BC), it has a 12-14 second burn time. It has been adopted for wide use in Sweden for first responders and distributed in Europe and Great Britain for a number of years, but expansion into the US has been limited by the lack of a UL rating. Made in China. $79.
Bottom line: Recommended. (Available via www.nordfireinc.com)
Firepal. Basically identical to the Maus Xtin. Distribution in UK only. £70.
Bottom line: Recommended.
Element E50. Also tiny (11.75” x 1.2”), the Element has a less intense but much longer 50-second burn time, with similar extinguishing capacity. This is much longer than a similar sized dry chemical extinguishers, which will be spent in 8-15 seconds. Direct comparison may be misleading, since the you can start and stop a dry chemical extinguisher. Made in Italy. $80.
Bottom line: Recommended. (Available at www.elementfire.com)
We like the compact size and reduced residue. However, the cloud is incredibly dense, the health effects are not well known, and the lack of a cut-off valve seems like a problem in the confined space of a yacht cabin. Dry chemical is messy and will make you cough, but has proven safe, the dust settles rapidly, and you can cut it off once the fire is out.
Carbon dioxide is a proven clean alternative, but they are bulky, expensive, and CO2 in a confined space can knock you out too. HFC 227 is expensive and hazardous in confined spaces. Bottom line? We’ll carry one of these as a back-up. They really do put fires out, although sheer volume of fumes can be intimidating inside a boat cabin.
Automatic Fire Suppression
A fire is one of the mariner’s greatest fears. We experienced a fire offshore once. It really gets your blood pumping when you realize there’s nowhere to go and help is a long ways off.
The first line of defense against fire is meticulous installation following ABYC guidelines. Next is maintenance. Corroded and faulty bilge pump wiring is probably the most common cause of fires in unattended boats. Or perhaps it’s an engine or galley fire.
Even when you are present and capable of fighting the flames, fire extinguishers don’t always work (many recalls). They require training to be effective, and often ruin the electronics in the process. They create choking fumes, and because of this, you can’t re-enter the space to mop up embers to prevent reignition. Because of these shortcomings, we reported on fire blankets and other practical firefighting alternatives (see PS June 2017).
Halon systems are an option, often seen in the engine rooms of large motor yachts. They aren’t actually Halon anymore—most are filled with heptafluoropropane, AKA HFC-227 or FR-200. They are expensive ($4,500 and up), require regular inspection, don’t like saltwater, and are not easily adapted to the many small spaces found on a typical sailing yacht. I’ve worked with these in refinery settings, and everything about them feels unsuitable for sailing yachts.
Tube-based fire suppression systems have simplified automatic fire suppression, making it practical in cars, light planes, and boats. Pressurized tanks, heat sensors and nozzles, are replaced with a proprietary polyamide (nylon) tube filled with the new Halon replacement fluid FM-200. The tubes are designed to resist compartment temperatures up to 158F for long periods.
If the tube experiences a temperature of 350F anywhere along its length, it ruptures in moments, releasing the entire contents in the direction of the heat source in a tiny fraction of a second. The space must be at least partially enclosed; however, the tube contents are released so rapidly that even if the space is well ventilated, the fire is extinguished before the agent can be dissipated. Ideally, the tube is located within 4 feet of the fire, and often, much closer is practical. By comparison, most single-tank HFC systems, such as the Xintex MA2, discharge at 175F, which is measured at a single point. One advantage of tank systems is a manual activation, handy when a fire is noticed before the heat sensor reacts.
Proteng THIA (tube + heat = instant action) tubes and Blaze Cut TD Series Tubes are warranted for four years. However, if protected from chafe they are expected to last far longer, up to 10 years. Inspection is a simple matter of visually confirming that the agent is still present (THIA tubes are translucent) or checking a gauge (standard from Blaze Cut, option from Proteng), and checking for loose clips or chafe.
The tubes are available in a variety of lengths, selected via a calculation to dispense the required amount of extinguishing agent. They must be secured with clips (conduit clips, electrical ties, or other sturdy means) every 10-14 inches. The tubes should be kept away from specific hotspots (turbochargers and exhaust pipes), but they should be located towards the top of the enclosure. Although remote monitoring of the fluid level is possible, it’s often simpler to install the tube where it can be visually inspected.
The list of possible installation locations is long: engine rooms, battery compartments, bilges, electrical panels, and machinery compartments.
Battery compartments present an interesting case. Lead acid batteries are a piece of cake. Install a few small tubes inside the case and they can snuff a fire out soon as it starts.
Lithium batteries are more complicated. They have a nasty reputation for thermal runaway and fire. The lithium iron phosphate chemistry used on boats appears to be much safer, and battery management systems prevent most dangerous scenarios, but the risk of fire remains and these fires are very difficult to extinguish once started. The FM-200 won’t do it. However, tube based systems may be effective in extinguishing battery case fires before they can contribute to thermal runaway. You’ll need to contact the factory about this application first.
Tube-based fire suppression systems are not FM or UL listed because there is no category for the product. If an automatic installation system is required by code a listed fire suppression system must be installed. Of course, in those cases, supplementing with tubes and using the tubes in small areas that are not protected by the main system provides a valuable backup.
Tube based fire suppression systems are not FM or UL listed because there is no category for the product. We interviewed two makers, Proteng and Blaze Cut. We handled the products, but we didn’t start a fire and put it out. They use a very similar hose material and the same fire suppression agent.
Perhaps the most concise summary was a comment by a user that “this is technology that isn’t technology.” Installed according to the instructions, the tube will always rupture when it gets hot, instantly filling the compartment with extinguishing agent. Saltwater doesn’t matter. No operator training. No cleanup. What could be simpler?
PS Technical Editor Drew Frye is the author of the book “Rigging Modern Anchors.” You can read his blog at www.saildelmarva.com.