NFPA 99, 2012 edition and most other editions have an “existing systems clause” helps to clarify that the requirements of the specific edition of the code are not meant to apply to existing systems. However, the clause also provides permission for the Authority Having Jurisdiction or compliance / accreditation agencies to require compliance where the existing conditions are considered a distinct hazard to life. A risk assessment should be conducted to ensure “there is no distinct hazard to life.” If it is determined that there is no concern for patient, public, or personnel safety, then the health care facility is permitted to continue to use the systems as is. This clause appears in the code, both the Administration Chapter and Chapter 5 for medical gas systems. See 188.8.131.52 and 184.108.40.206 for more info.
There are few joining methods allowed for vacuum piping systems in NFPA 99 (2021 edition) depending on the pipeline distribution system’s material. If the piping is copper tubing, silver solder brazed joints, axially swaged joint, and in some cases threaded joints are allowed. If stainless steel, then GTAW welded joints are required. NFPA 99 requires the same joining methods and procedures as required for the positive pressure systems. Having a procedure for field installation of the medical gas AND vacuum systems reduces the chances of using the wrong procedure for proper installation. Since these systems are usually installed side by side, having the one procedure to follow allows repeatability for these installers.
Many older vacuum systems do not have brazed joints because it wasn’t a requirement when these areas/facilities were built. Therefore, one has to ask if this existing condition creates a distinct hazard to life and poses a risk to patients. A risk assessment can be used to make this determination, but in most cases common sense would say that this condition does not pose a safety concern. So, one could document the compliance finding and perform a risk assessment to verify that this condition isn’t unsafe and can continue to be used as-is.
NFPA Disclaimer: Although Jonathan C. Willard is a principal member of the NFPA Technical Committee on Medical Gas and Vacuum Piping Systems, which is responsible for the applicable sections of NFPA 99: Health Care Facilities Code and a principal member of the NFPA Technical Committee on Industrial and Medical Gases, responsible for NFPA 55: Compressed Gases and Cryogenic Fluids Code, the views and opinions expressed in this message are purely the authors and shall not be considered an official position of the NFPA or any of its Technical Committees and shall not be considered, nor be relied upon as, a Formal Interpretation or promotion of the NFPA. Readers are encouraged to refer to the entire text of all referenced documents.