Non-condensables in a recovery cylinder raise the pressure at a given temperature because they are gases that do not condense with the refrigerant. When a cylinder contains both refrigerant vapor and non-condensables (like air), the total pressure reflects the contribution of all gases present. The refrigerant has its own saturated vapor pressure at that temperature, but the non-condensables add extra pressure that cannot condense away, so the overall pressure ends up higher than the refrigerant’s pure-vapor pressure. This is why charts that assume pure refrigerant don’t match the measured pressure if non-condensables are present. So the statement is true, and the idea that it only happens at high temperatures or that it’s unknown isn’t correct.

Signs that recovered refrigerant might be contaminated include an unusual odor, a color change, the presence of moisture or other impurities, and abnormal pressures observed during testing or charging. An unusual odor or color change suggests that non-refrigerant substances or degraded lubricants have mixed with the refrigerant, altering its properties. Moisture or impurities can come from leaks or improper handling and will change the refrigerant's behavior, often leading to incorrect readings and performance issues. Abnormal pressures indicate the refrigerant’s composition isn’t within spec, which can result from contamination and affect system operation and recovery equipment. Colder than expected ambient temperature isn’t a reliable indicator of contamination, as it can be caused by environmental conditions or system load. A smell like new plastic isn’t a typical sign of refrigerant contamination, and a slight metallic taste isn’t used as a practical or safe indicator in HVAC work.

Small-appliance service ports are designed for a simple, controlled access to the refrigerant circuit. The port consists of a straight piece of tubing called a process tube, and a piercing access valve is pressed into that tube to pierce and open the system when you’re ready to recover or recharge. This setup provides a secure, minimal-leak way to connect recovery equipment and seals the system when the valve isn’t being used. The other options don’t provide this pierceable, valve-enabled access: a threaded port with a cap can leak or be locked against access; a quick-connect fitting isn’t the standard design for small appliances; and a plastic cap with no valve offers no access at all.

Noncondensable gases are those that stay in the gaseous state at ambient (room) conditions. In a recovery cylinder, this means air, moisture, or other gases won’t liquefy under normal room temperatures and pressures. Their presence takes up volume and raises pressure, which can hinder efficient refrigerant recovery and skew measurements. The idea is that noncondensables do not condense into liquid at ambient conditions, unlike the refrigerant itself, which can liquefy under the right conditions.