Using a Refractometer: FAQ for Listed Antifreeze

Are you testing your UL-listed antifreeze with the wrong equipment?

NFPA Standards require the use of listed antifreeze in the majority of antifreeze fire sprinkler systems, whether new or existing. NFPA explains that “concerns of potential problems with the combustibility of antifreeze solutions used in fire sprinkler systems” led to the 2011 NFPA 25 requirement sunsetting traditional antifreeze mixtures by September 2022. A UL-listed solution increases safety by removing variable mixtures from the equation. These products are factory-premixed alternatives to traditional, site-mixed, glycol or glycerin solutions (though traditional mixtures are still permitted in some cases). While a freeze point test works for traditional antifreeze, listed antifreeze has different testing requirements and needs different tools. Here are some of the frequent questions we get about testing listed antifreeze with one common tool: a refractometer. 

Testing FAQ 

UL 2901-listed antifreeze is required to meet certain fire propagation requirements. Manufacturers of these products add proprietary ingredients to their listed antifreeze to control flame growth. These different ingredient mixtures mean that every manufacturer’s antifreeze will have a different composition, changing the ways they must be tested. After two annual maintenance cycles in the field, here are the most common questions we answer about testing. 

Can I Send My Antifreeze for Lab Testing? Should I? 

A lab test is a good idea if your system still contains unlisted fluid for freeze protection. This will confirm the fluid's composition, allowing you to make the best decision for your system moving forward.

However, on-site testing makes more economical and practical sense if your system has already switched to listed antifreeze. Although the proprietary blend is unique to each listed antifreeze manufacturer and not publicly available, the third-party approval gives you the confidence that testing to manufacturer’s specifications provides an accurate reading. 

Can I Use the Same Testing Methods for Listed Antifreeze that I Already Use for Unlisted Fluid?

A freeze point test is usually sufficient for unlisted fluids, as they are usually made of water and either glycerin or glycol. Listed antifreeze is made of a blend of ingredients, making freeze point testing unreliable.

Listed antifreeze must be tested using manufacturer-recommended tools and testing methods. The installation guide for any listed antifreeze will specify whether a hydrometer or refractometer should be used and what readings to look for using those tools. When a refractometer is recommended, testing must measure refractive index (RI) NOT using the Brix scale. Brix gives a reading on the sugar content using refractive index; because listed antifreeze contains no sugar, this is not an accurate test.  

Refractometer FAQ 

For many service technicians, a refractometer is new technology. Here are some of the most common questions about using a refractometer to test UL-listed antifreeze. 

Do I Have to Use a Refractometer? 

Those installing and using freezemaster™ antifreeze most often use a refractometer for accurate testing. Though the freezemaster™ antifreeze manual allows for either a refractometer or hydrometer for testing, hydrometers are more difficult to use in the field. A refractometer is the simplest, fastest way to get an accurate field reading.

Always refer to the listed antifreeze manufacturer’s installation guide to ensure you get the correct testing tool.  

Could You Give Me a ‘Refractometers 101’?

As with any new tool and method, there will be a learning period. It is essential to be patient with yourself. Patience will produce the most accurate test as you check multiple locations in the system. Allow the refractometer and system to equilibrate to get the best results. Although most refractometers can adjust for unequal temperature, equalizing temperatures helps ensure a faster, more accurate reading.

Perhaps the most important thing is to clean the testing well with distilled water before and after each use. Distilled water removes any residue from previous tests without introducing new material to the well that could alter test results. 

How Do I Choose the Right Model Refractometer?  

There are two types of refractometers: handheld and bench. Bench refractometers are more commonly seen in laboratory settings, as they aren’t designed to be mobile. Handheld refractometers are designed specifically for field use and are thus more common for listed antifreeze testing.

To test per UL 2901 requirements, your refractometer must do two things: measure refractive index and measure up to three decimal points. Beyond this, it’s largely individual preference. Labs at Lubrizol, the makers of freezemaster™ antifreeze, include a MISCO bench refractometer. Abbe also makes an excellent bench model. The MISCO handheld PA202 reads refractive index up to three decimal points, and the PA203 can be sent back to MISCO to add the software needed to read to three decimal points. Other handheld choices include Reichert 13940000 and Fisher Scientific Fisherbrand™. 

Can My Field Refractometer Test Any Listed Antifreeze?

Yes and no. A refractometer can test nearly any fluid. But not all listed antifreeze manufacturers provide the data needed to complete a test using a refractometer. Without this data, the RI produced will not be useful. The installation manual will confirm whether a refractometer may be used. One brand, for example, only specifies that a hydrometer may be used. And remember: it’s essential to measure only RI, not the Brix calculation. 

What If My Tests Come Back Out of Range?

Each listed antifreeze manufacturer includes testing data tables in its installation guide, along with the appropriate test method. This is the data for freezemaster™ antifreeze: 

The RI testing specification table for freezemaster™ antifreeze from its installation guide.

This data shows the allowable range for test results that are considered within specification. If testing returns an out-of-specification reading, try these troubleshooting steps: 

• Confirm your refractometer is set to RI and not Brix or another calculation setting.
• Carefully rinse the well with distilled water. 

If your repeated tests are still out of specification after troubleshooting, contact the antifreeze manufacturer.

Test Correctly for Increased Safety and Security

A tool is only as good as its proper use. Accurate annual testing ensures that your UL-listed antifreeze will deliver safety, performance and assurance you can rely on.

Contact the listed antifreeze manufacturer directly if questions or problems arise during testing. While the customer service team at your refractometer’s manufacturer may be happy to help, these tools have traditionally specialized in the beverage and brewing industry, so the toolmaker’s team may not have the answers you need. The freezemaster™ antifreeze team is available and ready to answer your testing questions, especially with handheld refractometers.