You should not reuse refrigerant unless tested to what standard?

The correct answer is based on the ARI 700 purity requirements, which set specific standards for the quality of refrigerant. When refrigerant is recovered for reuse, it must be tested to ensure that it meets these purity standards to avoid contamination issues and ensure system efficiency and reliability. These requirements specify acceptable levels of contaminants, such as moisture, acids, and non-condensables, which can significantly affect the performance of HVAC systems.

In contrast, EPA regulations primarily deal with the management and disposal of refrigerants to prevent environmental damage rather than the purity standards for reusable refrigerants. ASHRAE guidelines provide suggestions and best practices for various HVAC operations but do not specifically focus on the purity requirements for reused refrigerants like ARI 700 does. ISO standards address various aspects of international quality and safety for products and services but, again, do not specifically define refrigerant purity for reuse. Thus, the ARI 700 standard is the direct authority on this matter, confirming that refrigerant must be tested to those specific purity criteria before being reused safely in HVAC systems.