For commercial and industrial HVAC systems, managing temperature extremes and protecting system components with an efficient cooling system is critical. Whether you’re preventing freeze-ups in rooftop chillers or ensuring stable operation in variable climates, glycol offers dependable protection.

As a water treatment company with over three decades of experience, EAI has built a reputation for delivering high-performance, sustainable water and HVAC solutions across the Western U.S. Our team combines deep industry knowledge with practical field expertise to support system reliability, reduce energy waste, and extend equipment life.

In this article, we break down what glycol is, the different types, how it’s used in HVAC systems, and why proper maintenance is essential.

What Is Glycol?

Glycol is a versatile industrial compound found in HVAC systems, industrial chillers, automotive antifreeze, and even as a base ingredient in plastics and textiles. At room temperature, it is a viscous, colorless, and odorless liquid. It is highly soluble in water, forming effective antifreeze solutions that can lower the freezing point of water to as low as -60 degrees Fahrenheit. This is crucial for preventing freeze-ups in HVAC systems operating in extremely cold environments. Additionally, glycol has a high boiling point, enhancing its performance in high-temperature applications.

As a polar solvent, glycol can dissolve a wide range of water-soluble compounds and certain resins, making it useful in applications such as coatings, pharmaceuticals, and food processing. While it is less effective at dissolving nonpolar substances like oils and waxes, its solvent properties still make it a flexible ingredient in many formulations. Glycol is practically insoluble in petroleum ether, highlighting its limited solubility characteristics in relation to other solvents. Its high viscosity and humectant properties enable it to retain moisture and prevent drying out, which is particularly beneficial in products requiring long-term moisture stability.

Types of Glycol: Ethylene vs. Propylene

Ethylene Glycol

Ethylene glycol is derived from ethylene oxide which comes from ethylene. It is a highly effective antifreeze agent commonly used in industrial applications. Its ability to significantly lower the freezing point of fluids makes it ideal for operations in extremely cold environments. This type of glycol is known for its excellent thermal efficiency and is a reliable choice for systems that require robust freeze protection. Additionally, ethylene glycol is a precursor in the production of polyester fibers, which are widely used in the textile industry.

Due to its toxicity and the harmful byproducts produced as it metabolizes, it must be handled with care – with certain exposure risks without proper handling.

Propylene Glycol

Propylene glycol offers a safer alternative to ethylene glycol, particularly in settings where incidental contact with people or animals is possible. It is classified as food-grade and is often used in HVAC systems found in schools, hospitals, and other sensitive environments. While it does not provide the same level of thermal performance as ethylene glycol, its non-toxic substance profile makes it a preferred option where safety is paramount.

In a closed-loop water system, propylene glycol acts as a useful industrial compound, preventing water from freezing—thereby protecting system components. Though slightly less efficient in heat transfer, it still delivers dependable freeze protection and system stability. It can also be blended with corrosion inhibitors and is easier to store, handle, and dispose of responsibly.

How Glycol Works in HVAC Systems

Much like hydraulic brake fluids use glycol for pressure stability and temperature resistance, HVAC systems use glycol-water mixtures to circulate through coils, chillers, and heat exchangers for effective heat transfer. In colder climates, glycol prevents freezing in outdoor or rooftop systems. It also reduces system wear by preventing scale and corrosion. Typical HVAC blends contain 30–45% glycol, depending on climate and system requirements.

These properties, along with its corrosion protection and heat stability, are discussed further in the section on key system benefits.

Additional Benefits of Using Glycol in Cooling Systems

1. Freeze Protection
Glycol significantly lowers the freezing point of water, allowing HVAC systems to run year-round in extreme cold. It also offers freeze-burst protection, allowing the fluid to remain slushy without damaging components.

2. Corrosion Inhibition
Modern glycol blends contain corrosion inhibitors that coat internal surfaces, protecting pipes, pumps, and chillers from rust, scale, and biological fouling.

3. Extended Equipment Life
By minimizing freeze-thaw cycles and reducing corrosion, glycol extends the lifespan of system components and lowers maintenance costs.

4. Stable Heat Transfer
While water transfers heat more efficiently, glycol maintains temperature stability and protects systems in fluctuating or extreme environments.

Maintenance Best Practices for Glycol Systems

• Test Glycol Concentration Regularly: Ensure your glycol-to-water ratio matches your climate and system demands. Too little glycol won’t protect against freezing; too much can reduce heat transfer and increase fluid viscosity.
• Avoid Mixing Glycol Types or Brands: Mixing ethylene and propylene glycol, or incompatible brands, can cause fouling and system damage. Stick to one type and source.
• Monitor Inhibitor Levels and Fluid Quality: Inhibitors degrade over time. Regular testing for pH, alkalinity, and inhibitor strength is essential to maintain system protection.
• Inspect for Leaks: Glycol leaks are often subtle but can impair system performance and safety. Look for residue around pumps and fittings, and repair leaks promptly.
• Schedule Preventative Maintenance: Routine checks optimize glycol life and keep your HVAC system efficient. EAI can assist with testing, flushing, and performance evaluations.

Safety Precautions and Handling

Handling glycol requires adherence to proper safety protocols and awareness of chemical hazards. Both ethylene and propylene glycol can cause skin and eye irritation and can be considered toxic compounds. Inhalation of vapors may lead to serious upper respiratory tract issues, and ingestion—especially of ethylene glycol intoxication—can be fatal. Always handle glycol in well-ventilated areas while wearing protective clothing and eyewear, following safety guidelines and standards related to hazardous materials.

Store glycol in a cool, dry place away from ignition sources. In the event of skin or eye contact, wash the area thoroughly and seek medical attention if symptoms persist. Decontamination is crucial to remove toxic substances for safety. Inhalation requires immediate access to fresh air. Ingestion of glycol requires urgent medical intervention.

Monitoring and Analyzing Glycol Concentration

Ensuring proper glycol concentration isn’t just about topping off fluids — it requires precise monitoring. EAI technicians use portable refractometers or glycol test strips for quick, on-site assessments of glycol concentration. These tools provide fast readings to verify freeze protection levels and ensure day-to-day system performance. While not as precise as lab instruments, they are essential for routine maintenance checks and initial troubleshooting. and lab-grade analysis to maintain system integrity and efficiency. Several analytical methods are also available to measure glycol in HVAC systems and related environments in a lab environment:

• Gas Chromatography (GC): Ideal for separating and detecting glycol in air, water, and industrial samples. Often used in environmental monitoring or contamination detection.
• High-Performance Liquid Chromatography (HPLC): Effective for analyzing complex fluid mixtures, especially in routine system checks where other chemicals may interfere with readings.
• Spectrophotometry: A simpler lab method for measuring glycol concentration based on light absorbance. Useful for routine service checks and system performance monitoring.
• Titration Methods: Common in HVAC maintenance labs, these involve neutralizing glycol solutions to measure concentration — ideal for on-site quality control.
• Mass Spectrometry (MS): Used in more advanced settings, often paired with GC or HPLC to identify glycol in contaminated or biological samples.
• Enzymatic Assays: Typically used in medical or environmental labs, these methods detect glycol through enzyme reactions — highly sensitive but less common in routine HVAC work.

Environmental Considerations and Compliance

Ethylene glycol is widely used across industrial applications, but improper handling or disposal can pose serious environmental risks. If released into soil or waterways, it can harm aquatic life and potentially contaminate drinking water sources. Its sweet taste also makes it dangerous to animals through accidental ingestion.

To minimize these risks, agencies like the EPA, OSHA, and NIOSH have established strict guidelines for safe use, storage, and disposal. These include:

• Spill prevention and secondary containment
• Proper ventilation and PPE for worker safety
• Waste management protocols to reduce environmental impact

EAI supports clients by providing compliant glycol solutions and expert handling practices that align with federal and state regulations. Our approach ensures safety, system performance, and peace of mind when it comes to environmental responsibility.

EAI’s HVAC Glycol Cooling Systems Expertise

At EAI, we understand that effective glycol management is essential to HVAC system performance and longevity. That’s why we offer tailored glycol solutions—from selecting the right type and concentration to ensuring system compatibility and protection.

With over 30 years of experience in water treatment and system optimization, our team delivers full lifecycle support. EAI also helps clients stay ahead of evolving regulations by offering expert guidance on glycol selection, usage, and disposal practices that align with local, state, and federal requirements.

Contact EAI today to schedule a consultation or fluid analysis with one of our specialists. We’re here to help your system perform at its best, every season.

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