A man tries to put out a fire with a small extinguisher
A man tries to put out a fire with a small extinguisher

Portable Fire Extinguishers

Foundation Findings #27 - May 1997

Of all the hazards on the high seas - wind, weather, risk of collision - fire aboard ship is the most feared by mariners. Recreational boaters should be no less concerned.

Property losses from boat fires exceeded $5,000,000 in 1994 and the half dozen deaths recorded that year were six too many.

But although the U.S. Coast Guard has required recreational boaters to carry approved fire extinguishers aboard most classes of powerboats and auxiliary sailboats since 1940, there is no expiration date requirement for fire extinguishers as there is for visual distress signals.

The BoatUS Foundation for Boating Safety decided to find out if old extinguishers that had been aboard boats for years would perform as well as new units.

We designed a test to compare a selection of veteran extinguishers with brand new units in the three sizes commonly carried aboard recreational boats.

Fire Fighting ABCs

But, before we report on the test, it's important to know some of the nomenclature. Fires are grouped into four classes:

  • Class A: Normal combustibles like paper, wood, cloth.
  • Class B: Combustible liquids like alcohol and engine fuels.
  • Class C: Electrical fires.
  • Class D: Combustible metals.

Extinguishers are rated by their effectiveness in controlling one or more fire types. For example, an ABC-rated extinguisher would be effective for Class A, B, and C fires. Numbers preceding the letters indicate relative effectiveness in extinguishing that particular class of fire. For instance, the most commonly carried unit, the 10 BC, which contains 2.75 pounds of dry chemical fire suppressant, is rated "twice as effective" as the 5BC, which has two pounds of chemical, in fighting fuel and/or electrical fires. The next size, the 3!-40BC, with five pounds of chemicals, would be even more effective.

Be sure your extinguishers are marked "U.S. Coast Guard Approved", since these have non-corroding hardware suitable for use aboard a boat.

Does Age Matter?

For this Foundation Findings, our test coordinator collected 13 fire extinguishers from a variety of boats in our area to compare with fresh-out-of-the-box units. These extinguishers had been through hot, muggy, Chesapeake summers and sub-zero winter weather. As far as we could determine, they had had no service or maintenance.

In all likelihood, most hadn't been out of their mounting brackets since installation. They ranged in age from seven to 16 years, with an average age of 9.6 years.

For testing, we collected five type 5BC, eight type 10BC and one type 3A-40BC. We then compared them type-for-type against new units dated 1995 and 1996, although of the 30 new units purchased for testing, nine had no date. (More on that later.)

The new vs. old test compared four factors: time of discharge, effective discharge distance, pattern width at six feet from the nozzle, and maximum pattern width at the end of the unit's effective range.

Using a stopwatch and camera, we photographed each discharge sequence against a control grid marked off in one-foot squares. Each unit was weighted prior to testing to determine fire suppressant content before and after.

In every test criterion, the new extinguishers outperformed the old by slight margins. Overall, the new extinguishers recorded a 12.6 percent longer discharge time (14.23 sec vs. 12.64 sec) and six percent greater distance (11.28 feet vs. 10.63 feet).

Discharge pattern width at six feet (the recommended distance to stand from a fire) for the new units came in seven percent wider. And maximum pattern width proved 12 percent wider for the new units vs. the old.

Is More of a Good Thing Better?

The tests also compared the relative efficiency of the three model types, this time combining both old and new units in their respective classes. In comparing the smallest units, the 5BC, with the 10BC, we found that overall performance - discharge time, distance, pattern width - improved a very modest 1.5%. But between the 10BC and the 3A-40BC, performance jumped and impressive 37%.

According to the manufacturer's product description on the box, the 10BC has "twice the fire fighting power" of the 5BC. But is that meaningful information? This statement applies to controlled laboratory conditions but in practical terms, boat fires don't burn that way.

In our tests, the 10BC units discharged only a fraction of a second longer than the 5BC, hardly "twice" anything. The 10BC, on average, discharged only 25% more fire suppressant than the 5BC. So we question whether the manufacturer's statement is meaningful in any real sense.

The packaging for the 3A-40BC, on the other hand, makes no similar claim. Yet, on average, the 3A-40BC gave a 44% longer discharge time and discharged 115% more fire suppressant than the 10BC.

Real World Testing

Coast Guard regulations require only BC extinguishers aboard recreational boats. But a flammable liquid or electrical fire aboard a boat can quickly become a type A when it spreads to locker doors, food packaging, curtains, bedding, and the like. So to compare the effectiveness of BC fire extinguishers on class A fires, we cooked up our own boat fire using wood chips, shards of fiberglass and stove alcohol.

We compared new 5BC and 10BC units and found that each could smother the same size fire by knocking down the flames with one or two short bursts. But within less than a minute each time, the fire came back to life.

The advantage to a BC unit in these conditions is that it would put out any flammable liquid or electrical component of a fire while also slowing down the "A" components until you can get water on it.

But, as a practical matter, it makes sense to outfit a boat with tri-class, ABC extinguishers to the extent practical. (The smallest units are available in BC only, however.)

Quality Control

Given the small number of new units in this test (30), we encountered an unusually high number of quality control problems. The most alarming was a new 10BC extinguisher that flat-out did not work. Although the weight checked out, the gauge was in the red.

We shipped that unit back to the manufacturer, Walter Kidde, Inc., who traced the problem to a dried out O-ring that had cracked, causing the unit to lose pressure. The company maintains the problem is not common but has made design improvements to prevent this. (The message is: Check the gauge when you buy the unit and every six months thereafter.)

Of the five 3A-40BC extinguishers purchased, four came without hose retainers, two had no hose at all and one had two hoses! This was especially peculiar since we bought them from two different distributors.

Of the 30 units, 21 had a separate UL sticker showing the year of manufacture while the rest displayed the UL approval on the manufacturer's product information label but had no date.

Lessons Learned

Given the differences in performance of old units versus new, would we buy all new fire extinguishers for our boat? No. But we would certainly consider adding a unit or two beyond minimum USCG requirements. Where space allowed, we would move up to larger units, certainly from the two-and-one-half pound unit to the five pound (i.e., from a 10BC to a 3A-40BC).

Other Recommendations

  • Turn your units over periodically. The older units tested consistently failed to discharge all fire suppressant which most likely caked up at the bottom.
  • For units that can be serviced, have them checked annually. For the smaller units, check the gauges twice a year.
  • Practice putting out a test fire on land with the type of extinguisher you carry on your boat. The cost of a disposable unit or a recharge is money well spent.
  • Review fire extinguisher location and the basics of operation, even to the point of test drills with all crew and every new guest who comes aboard. (It goes without saying that you do that already with your life jackets and other emergency equipment, right?)

U.S. Coast Guard Minimum Requirements (1997)

All extinguishers must be Coast Guard approved
  • Boats less than 26 feet - At least one 2-lb hand-portable extinguisher (assuming no fixed-fire extinguishing system is installed). When an approved fire extinguishing system is installed in machinery spaces, no extinguisher is required. If construction of the boat does not permit the entrapment of explosive or flammable gases or vapors, no fire extinguisher is required.
  • 26 to less than 40 feet - At least two 2-lb portables, OR at least one 2.5-lb. When an approved fixed-fire extinguishing system is installed, one less 2-lb is required.
  • 40 to not more than 65 feet - At least three 2-lb portables, OR at least one 2-lb PLUS one 2.5-lb. When an approved fixed-fire extinguishing system is installed, one less 2-lb is required.