What role does cylinder fill percentage play in refrigerant handling and what safety precautions should be followed?

• A. Do not fill a cylinder beyond 60% of its capacity for liquids; never weigh.
• B. Do not fill beyond 80% of cylinder capacity for liquids; weigh to verify charge; keep cylinders upright and away from heat; use proper PPE.
• C. Fill cylinders to 100% to maximize storage.
• D. Only fill while cylinders are lying on their side.

Answer: (B)

The key idea is that filling a cylinder with refrigerant must leave space for expansion and be verified with a precise charge. Liquids expand with temperature and the gas inside will also pressurize as the cylinder heats, so leaving headspace prevents dangerous overpressure and venting. Filling to about 80% of the cylinder’s capacity is the standard rule for liquids because it provides enough room for expansion while maximizing usable capacity. Verifying the charge by weighing the cylinder is essential because volume alone can be misleading due to variations in temperature and liquid density; scale measurement gives a reliable check that the exact amount loaded matches the desired charge, not just the apparent fill level.

Keeping cylinders upright and away from heat sources is important to avoid liquid moving toward the valve or overheating the cylinder, which could raise pressure or cause venting hazards. Proper PPE is needed to protect against cold burns from liquid refrigerant, skin and eye exposure, and inhalation risks during handling and charging.

Filling to 100% neglects the expansion you must accommodate, placing the cylinder at risk of overpressure. Lying cylinders on their side can complicate venting, pose handling hazards, and increase the chance that liquid ends up in the valve area.