by Grant Lobdell

The current, 2018 edition of the National Fire Protection Agency (NFPA) 10 Standard for Portable Fire Extinguishers requires dry chemical agent to be thoroughly checked for proper type, contamination, and condition before reuse (7.8.3.4.3).

Is a visual inspection thorough enough?

While not required explicitly in the standard, laboratory testing of dry chemical agent is recommended by Dyne. Proper type, contamination, and condition often cannot thoroughly be verified by a visual inspection. While most manufacturers do dye their products based on type (ABC, BC, etc.), different products of the type often will appear to be the same color. For example, Ansul’s Foray ABC dry chemical agent (Part Number 53080) and Badger’s Multipurpose ABC dry chemical agent (Part Number 18905) are both yellow. However, the chemical composition of the two are quite different, mainly in their concentration of monoammonium phosphate and ammonium sulfate. Whereas the Ansul agent referenced contains both monoammonium phosphate and ammonium sulfate, the Badger agent referenced opts for a much higher concentration of monoammonium phosphate without any sulfate additives. Agents and the extinguishers designed for use with those agents may achieve different ratings when listed in part due to different chemical compositions. Failure to reinstall the proper agent listed with an extinguisher can result in an extinguisher failing to perform as designed at the worst possible time.

Furthermore, the visual inspection for moisture, one of the most common forms of contamination of a dry chemical agent, can be limited. The current, 2018 edition of International Organization for Standardization (ISO) 7202 Fire Protection – Fire Extinguishing Media – Powder requires a dry chemical agent contain less than 0.25% of moisture. From our experience, by the time caking is observed visually, the agent is well past the 0.25% cut off. An agent with 0.25% moisture will still typically appear free of caking and flow freely to the naked eye.

How often should I be testing my dry chemical agent?

For portable extinguishers where the agent is stored in a sealed, pressurized vessel, the agent only needs to be retested before reuse. This could be after an event where an extinguisher was partially discharged, and the extinguisher is to be topped off by a certified service technician. This could also be during the periodical tear down and inspection as required by NFPA 10. If you are an end-user or an authority having jurisdiction (AHJ), such as a fire marshal or an insurance company representative, looking to verify proper filling techniques have been used to service extinguishers at a facility after refilling has occurred, it is recommended that a random sample of extinguishers be chosen to represent the group given the cost of testing vs replacement. This approach is similar to how a random sampling of fire sprinklers in an area are selected and tested to represent that area.

If you are a service provider looking to reduce your risk and document proper filling techniques for your records, Dyne recommends testing a sample of the agent that is collected in the required closed recovery system before it is reused. This will allow a great amount of agent to be tested and verified at once, reducing the cost of analysis per extinguisher. Note that great care should be taken when removing agents from multiple extinguishers at a time using a closed recovery system. Only those extinguishers believed to contain the same agent should be collected at the same time to avoid mixing of different agents. If an extinguisher being serviced has been previously serviced by your company in the past and has adequate maintenance records, you should be confident of the agent installed. If an extinguisher has been previously serviced by another company and/or adequate maintenance records can not be found/obtained, you may be rightfully hesitant to mix its agent with another.

For fixed systems, the current, 2017 edition of NFPA 17 Standard for Dry Chemical Extinguishing Systems requires an examination of the dry chemical agent in a stored pressure system at least every 6 years (11.3.1.2). If the dry chemical agent is stored in a non-pressurized vessel for the fixed system, examination of the dry chemical agent shall occur at least semiannually and after any system activation (11.3.1).

For those adhering to the requirements of International Maritime Organization (IMO) 1432 Revised Guidelines for the Maintenance and Inspection of Fire Protection Systems and Appliances (current edition dated 31 May 2012), the dry chemical agent must be laboratory tested for moisture content every 2 years (8.2.4).

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