Industrial heat transfer fluids are non-freezing liquids for heating, cooling, air conditioning, solar collector, and ice rink systems. Base: ethylene glycol (toxic, for closed systems) or propylene glycol (non-toxic, for food industry). Glycol concentration 30–65% determines crystallization temperature: 30% — down to −15°C, 45% — down to −30°C, 65% — down to −65°C. Additive package: corrosion inhibitors (silicates, carboxylates — OAT technology), anti-foaming agents, pH stabilizers. Service life: 5–10 years (OAT) or 2–3 years (silicate). GOST 28084-89. Packaging: canisters 10–50 l, barrels 200 l, IBC 1000 l. Color: red, green, yellow — for visual identification. OAT technology (Organic Acid Technology) — carboxylate-based additives, free of silicates, borates, nitrites. Do not form deposits, compatible with aluminum heat exchangers. Replacement: after 10 years or when pH drops below 7.0. Quality control: pH, density, alkalinity, glycol content (refractometer). Documentation: quality certificate, MSDS, ASTM D1384 certificate.