To test a sample containing propylene glycol from a two inch anti-freeze loop in a building with a 4 inch wet pipe system and a 4 inch pressure zone back flow preventer fed by a non potable water supply, which tool should be used?

• A. Anemometer
• B. Refractometer
• C. Spectrometer
• D. Tachometer

Answer: (B)

Measuring the glycol concentration in an antifreeze loop is the essential task here. A refractometer is the best tool because it directly reads the liquid’s refractive index, which changes with the amount of propylene glycol in water. That refractive index is then correlated to percent glycol or a corresponding freezing-point value, giving a quick, on-site measurement of the mixture to ensure it’s within design and safety requirements for freeze protection and system integrity.

The other tools aren’t suited for this job. An anemometer checks air flow, not liquid chemistry. A spectrometer can analyze light from a sample but is not the practical, routine method for determining glycol concentration in field HVAC testing. A tachometer measures rotational speed of a component, which has nothing to do with the chemical composition of the loop fluid.