By Grant Lobdell
According to the 2018 edition of National Fire Protection Association (NFPA) 10 Standard for Portable Fire Extinguishers, only dry chemical agents “specified on the nameplate or agents proven to have equal chemical composition, physical characteristics, and fire-extinguishing capabilities shall be used.” (7.8.3.1) Furthermore, “prior to re-use, the dry chemical shall be thoroughly checked for the proper type, contamination, and condition.” (7.8.3.4.1)
Determining Dry Chemical Type, Contamination and Condition
For many years, contractors have determined a dry chemical’s type, contamination and condition visually. The color is often an indicator of the type where ABC agent is typically yellow, BC agent is typically white or blue, and purple-K agent is usually purple. The contamination and condition of the agent is typically verified by looking for notable clumps in the fine powder, known as caking, which would indicate moisture contamination. The problem with these visual examinations is twofold:
- there is no requirement that an agent be a certain color in most, if not all, current listing standards including UL 299 Standard for Dry Chemical Fire Extinguishers, EN615 Fire protection – Fire extinguishing media -Specifications for powders (other than class D powders), and ISO 7202 Fire protection – Fire extinguishing media – Powder.
- the prevalence of closed recovery systems, which transfer dry chemical agent at relatively high pressure, can mask any moisture issues by breaking up any caking before the visual inspection is conducted.
Laboratory analysis would be much more thorough than visual examinations. To determine the dry chemical type, Dyne utilizes an analytical technique called ion chromatography. The agent is dissolved in a solvent which is then injected into a column designed to separate the ions. The ions coming off the column are then quantified using conductivity. With this technique, Dyne is able report the amount (%) of each of the following components found in the dry chemical agent:
- Monoammonium Phosphate (Main ingredient in ABC agents)
- Sodium Bicarbonate (Main ingredient in BC agents)
- Potassium Bicarbonate (Main ingredient in purple-k agents)
- Ammonium Sulfate (Secondary ingredient in some ABC agents)
- Calcium Carbonate (Secondary ingredient in some BC and purple-k agents)
Dyne can detect as little as 1% of each of these components in the sample tested.
To evaluate the dry chemical contamination and condition, Dyne measures the moisture content of the dry chemical samples using an analytical technique called Karl Fisher titration. The moisture in the sample is driven off by exposing the sample to high temperatures and dry air. The moisture is collected in the dry air flow which is transferred to a collection vessel where it is quantified by monitoring a resulting electrolysis reaction. With this technique, Dyne can report the amount (%) of moisture as low as 0.01%.
The Requirements
The concentration of each component is compared to manufacturer specifications. According to the 2018 edition of ISO 7202 Fire protection – Fire extinguishing media – powder, section 5.4, a dry chemical agent must be within ±1% (for components designed to be between 10-15%), ±1.5% (for components designed to be between 15-25%), ±2% (for components designed to be between 25-65%), or ±3% (for components designed to be above 65%) of the manufacturer declared concentration. For example, Badger’s Multipurpose ABC dry chemical agent is advertised to contain 90-97% monoammonium phosphate. For Dyne to designate this sample as passing the monoammonium concentration requirements, the sample must contain 87-100% monoammonium phosphate.
Dyne’s state-of-the-art dry chemical testing laboratory
The 2018 edition of ISO 7202 Fire protection – Fire extinguishing media – powder, section 10, states that the moisture content of a dry chemical agent should be <0.25%.
Why Testing is Important
A sample reported as failing one or more of the chemical composition requirements can be a concern for a variety of reasons:
- A sample that is found to have low main ingredient concentration(s) may have reduced fire extinguishment performance. The concentration of the main ingredient is proportional to that agent’s performance.
- A sample found to have higher than advertised concentration of any of the components can indicate the sample is not the agent indicated. Remember that UL only evaluates an extinguisher’s performance with its listed agent(s). For this reason, the 2018 edition of NFPA 10 requires “only those agents specified on the nameplate or agents proven to have equal chemical composition, physical characteristics, and fire-extinguishing capabilities shall be used” (7.8.3.1).
- A mixture of agents can cause dangerous reactions to occur. Specifically, mixing of ABC and BC agents can cause ingredients in the two to react, producing carbon dioxide and water byproducts. The carbon dioxide can over pressurize containment vessels. The 2009 edition of EN 615 Fire protection – Fire extinguishing media -Specifications for powders (other than class D powders) states the following in Section 7 Chemical Content: “Such increases in pressure have been known to cause containers to rupture, and to cause bodily injury and damage.” Furthermore, the water produced by the reaction of ABC and BC agents can cause caking thus impacting the agent’s ability to flow through the equipment as designed.
Code Compliance
Dyne’s dry chemical testing service fulfills requirements found beyond those detailed above from NFPA 10. For example, according to the 2017 edition of NFPA 17 Standard for Dry Chemical Extinguishing Systems, NFPA’s standard governing fixed dry chemical systems, “at least semiannually [stored pressure systems every 6 years] and after any system activation, maintenance shall be conducted in accordance with the manufacturer’s design, installation, and maintenance manual.” (11.3.1) The standard goes on to describe what this maintenance involves including “examination of the dry chemical.” (11.3.1.1)
Furthermore, International Maritime Organization (IMO) MSC.1/Circ. 1432 dated 31 May 2012, under Section 8 Two-year testing and inspections, states that the dry chemical powder from fixed dry chemical powder systems shall be tested for moisture content. (8.2.4)
How to utilize Dyne’s Dry Chemical Testing Service
As is true for the majority of our services, Dyne offers free sample kits with free shipping both ways (in the contiguous United States) for this service. It is important to utilize these sample kits, not only for the cost savings, but to be sure the agent is not compromised during shipment. Dyne’s dry chemical sample kit features a 60 mL (about 2 oz) sample container that is designed to keep moisture out during transit, so the sample stays representative of the dry chemical agent at the time of sampling. To request a sample kit, visit dyneusa.com, email lab@dyneusa.com, or call (800) 632-2304.
Dyne’s Dry Chemical Sample Kit.
Note that Dyne will not sample any extinguishers sent directly to Dyne. As an independent laboratory, we do not have access to the required OEM parts nor are we certified to put extinguishers back into service after sampling.
Results are guaranteed within 5-business days upon sample receipt (24-hour turnaround is available for an added fee). Contact Dyne for current pricing information.
If you have any questions regarding this article, please contact Dyne Fire Protection Labs at lab@dyneusa.com or (800) 632-2304.
©Dyne Fire Protection Labs 2020