By Alyssa Dunn, General Manager, Dyne Fire Protection Labs
The most current edition of NFPA 25 Standard for Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems 2023 Edition recommends antifreeze solutions be tested annually toward the beginning of heating season prior to the onset of freezing conditions. This annual testing is recommended for both listed antifreeze solutions and legacy solutions such as propylene glycol and glycerine.
There is some confusion regarding the use of listed antifreeze solutions vs the use of legacy solutions. Previous editions of NFPA 25 required legacy solutions to be replaced with a listed alternative by September 30, 2022. However, the 2023 Edition of NFPA 25 now allows legacy solutions to remain in service if those solutions meet certain concentration limits. For propylene glycol solutions, the concentration cannot exceed 30% by volume and for glycerine solutions, the concentration cannot exceed 38% by volume. There is one exception to these limits – premixed propylene glycol solutions exceeding 30% by volume are permitted for use with ESFR sprinklers if the ESFR sprinklers are listed for such use. Outside of this exception, if antifreeze systems are drained for any reason or if the concentration of the solution exceeds the allowed concentration percent by volume, the system shall be drained and refilled with a listed solution.
If the antifreeze solution is not required to be replaced, test samples shall be taken at the top and bottom of each system. In addition, if not already accounted for in the top and bottom test points, samples shall be taken at the most remote portion of the system and at the connection to the water supply. If the antifreeze system has a capacity larger than 150 gallons, additional test points are recommended for every 100 gallons.
For each sample, the specific gravity or refractive index shall be checked. This test can be completed in the field provided the appropriate calibrated equipment such as a hydrometer with a suitable scale or a refractometer is available. In the event this equipment is not available or if you would prefer an independent laboratory conduct the analysis, Dyne Fire Protection Labs, an NFPA Global Solutions Company, can test your antifreeze solution.
For legacy solutions, the concentration by volume can be determined by measuring the refractive index or density. Some equipment available for use in the field are calibrated to convert the specific gravity or refractive index into a percent concentration. If your equipment does not convert to concentration, a conversion chart such as the one found in Table A.5.3.4.4.2 of NFPA 25 2023 Edition can be used. If your solution falls outside of the allowed concentration limits (30% by volume propylene glycol or 38% by volume glycerine), the antifreeze solution must be replaced by a listed solution. It is important to note that whether you are using a calibrated meter or a conversion chart to test your samples, the type of legacy solution must be known to get accurate results.
When testing listed antifreeze solutions, the specific gravity or refractive index shall be within the range listed as acceptable by the manufacturer – usually found on the product’s technical datasheet. Listed antifreeze testing is slightly different as there is no need to determine the percent concentration of the solution. If the specific gravity or refractive index falls outside the acceptable range for the listed product, further investigation or replacement may be necessary.
Whether you are testing your legacy antifreeze or listed antifreeze solution, it is important to know the type of solution you have. If you are unsure of the type of solution in your system, Dyne Fire Protection Labs can help differentiate between both legacy and listed solutions. Legacy solutions can be differentiated using refractive index and density whereas listed antifreeze requires testing for concentrations of additives in the sample and matching to known compositions of listed antifreeze products. If the type of antifreeze cannot be determined or if the type is no longer permitted, the system would need to be drained and refilled with an acceptable solution.
If you have any questions regarding this article, please contact Dyne Fire Protection Labs at dyne.lab@nfpaglobal.com or (800) 632-2304.
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