Volume 9, No. 3 • Fall 1994

Shutdown of Gas Supply System Need Not Be Danger

Todd G. Peterson, MD; Fred Evans, PhD

Planning Minimizes Risks

Editor’s Note: This paper is one of a series on medical gas and vacuum systems to be printed in the Newsletter. Dr. Ervin Moss, a member of the Board of Directors of the Anesthesia Patient Safety Foundation and the chairman of the APSF Subcommittee on Medical Gas Vacuum Systems, is coordinating the series.

by Todd G. Peterson, MD, and Fred Evans, PhD

Anesthesia personnel in most operating room settings have come to rely on the Medical Gas Pipeline System (MGPS) as a dependable, very rarely interrupted supply of gases used in the delivery of anesthesia. Tanks are seldom used now except in the administration of anesthesia in places remote from the operating room or in the transportation of patients. As a consequence, anesthesia personnel often lack familiarity with backup plans when medical gas pipelines are shut down for periods of time longer than their machine mounted tank supplies would last. In a planned shutdown of the MGPS, whether for maintenance, modifications or repair, the Anesthesiology Department needs to actively participate throughout the process to assure the uninterrupted flow of gases necessary for safe patient care.

Stages Outlined

A planned shutdown of the MGPS involves three stages: the project definition and preparation prior to shutdown, the actual shutdown and modification of the MGPS, and the recertification of the system after repressurization. Key to minimizing downtime and risks to patients throughout this process are effective communication, preparation, and coordination between hospital departments and services affected by the shutdown and the contractor making modifications. Shutdowns without adequate communication among all those involved have resulted in near crisis situations and even some overt accidents. (1)

The planning process begins with a definition of the scope of the project and should ultimately produce a comprehensive, written shutdown procedure to accomplish the task. The planning process requires an up-to-date, accurate plan of MGPS as actually constructed. Despite the JCAHO requirement for hospitals to have this on file, it is not uncommon for the institution to only have the architect’s original plans. (2) In this situation, a careful ‘hand over hand’ tracing of the system to verify and update the drawings is indicated to prevent unexpected loss of gas supply, prevent construction errors, and minimize downtime, This is also a good time to have a consultant or the internal engineering department reevaluate the MGPS to verify that it continues to meet code requirements and initiate any indicated modifications.

The contractor uses the MGPS drawings to determine how extensive a shutdown is required, to accurately identify the areas affected during the shutdown, to locate valves required for shutdown, and to reasonably estimate downtime. The MGPS, if designed correctly, incorporates a series of shut-off and control valves which include:

1. The source valve located externally directly downstream of the bulk source equipment.

2. The main shut-off valve normally the first valve inside the facility.

3. Riser valves located at the base of each riser in multistory buildings.

4. Floor valves though not required, they are located at each branch off the riser and are used to isolate an entire floor.

5. Zone valves located at eye level along a corridor wall for control of specific areas.

These valves allow for three basic types of shutdowns:

1. Complete shutdown usually done to tie-in a future line to the main or for repairs to the bulk supply source.

2. Riser shutdown: usually done for modifications to an area of the hospital supplied by a single branch (or riser) off the main line.

This most frequently involves service, replacement, or movement of zone valves.

3. Zone shutdown: usually done when desired remodeling and repairs are downstream of specific zone isolation valves.

Prior to any shutdown, the valves required to isolate the construction area are located and tested for internal leakage. Leaky valves can allow nitrogen used in the brazing process to enter and contaminate adjacent zones, or can prevent the plumbers from achieving the gas concentrations within the pipeline required for brazing (0% 02, 100% N2).

Once the contractor determines the extent and duration of shutdown required, the services affected by the shutdown should meet with the contractor to decide on the optimum time and date for the shutdown, to choose a method for supplying medical gases to each patient until the central gas supply is restored, and to define equipment, manpower, and gas supply requirements for that interval. If the shutdown will affect relatively few patients, the simplest alternative supply is through individual supply cylinders, regulators, and backup cylinders for each patient. Patients on ventilators require multiple supply tanks since a single Bear or Servo ventilator uses an “H” cylinder every 4 hours.(3) When larger areas of the hospital are involved, the task of coordinating equipment, supplies, and staff can become very complicated and expensive.

Another acceptable method of supplying the entire system or a portion of a system during a shutdown is to back-feed sections of the MGPS isolated by closing valves either at the riser, branch lines, or zones. Gases are backfed into these sections through inlets placed downstream of the valves. Some such inlets may already exist, such as the Emergency Oxygen inlet which is often used when work is performed on the bulk oxygen supply. Frequently though, inlets need to be installed prior to the planned shut-down. This usually requires a more limited zone shutdown to add an 3″ collar inlet downstream of a zone valve. The contractor usually adds these collars to zones which receive little or no use to minimally affect patient care. The inlets must be capable of supplying the flows required by the isolated section without a significant pressure drop or equipment may not function properly. If adequate flow cannot be supplied through a single inlet, the area to be isolated can be broken down into multiple isolated zones, each with an inlet, to meet the anticipated total flow required to provide an adequate alternate supply for each patient’s needs.

Though not recommended, some MGPS outlets are used as inlets to back-feed a zone. This is generally considered risky as most outlets are flow limited as a result of their relatively small internal diameter. The use of outlets requires careful verification of adequate back-feed flow capacity prior to their use for a shutdown.

The flow requirements and the expected duration of the shut-down determine the type of alternative gas supply chosen. Large stainless steel containers filled with liquid oxygen, called Liquid Dewars, supply large volumes of oxygen, but are limited in the peak flow they can deliver. High pressure cylinders manifolded together in a ‘six pack’ contain smaller volumes of gas, but are capable of much higher peak flows. Combinations of Dewars and ‘six packs’ are sometimes used when high peak flow and high volume use are anticipated. A Y-adapter with check valves attaching the back-feed inlet to the tank supplies permits easy change-over of tanks.



1. How many patient beds will be affected by the shutdown?

2. Of these beds, how many will be occupied by patients requiring pipeline supplies? Which pipeline supplies will be shutdown?

3. How many patients affected by the shutdown will be on ventilators?

4. How many and what brand of ventilators do you use?

5. How many operating rooms will be affected by the shutdown? What OR pipeline supplies will be affected? Which OR pipeline supplies will require alternate sources?

6. How many emergency room beds will be affected by the shutdown?

7. Based on the alternate supply technique chosen, what type and how many flow regulators are needed for floor beds? For ICU beds? For the ORs?

8. Based on the expected maximum duration of the shutdown, what type of gas supply source and how many will be needed for floor beds? For ICU beds? For ORs?

9. How many support stands are needed? Transportation carts? Y-pieces? What other special equipment is required?

10. How much liquid nitrogen will be required for the purge?

11. How many trained staff can be available for the shutdown? How long can they be available? What training have they had?

12. How many personnel will require radio communication equipment?


Based on the alternate gas supply method chosen, each affected service notifies, trains, and schedules adequate numbers of staff to handle any potential problem during the shutdown. Adequate supplies of equipment and gas sources are ordered and a plan for distribution developed. Table I contains a set of questions often used to help determine the equipment and gas supply requirements. If back-feeding a zone is planned, local pipeline supply alarms, especially in critical care areas and the operating rooms, must be tested for proper function. Meanwhile, the MGPS contractor obtains all pipeline components, prefabricating and pressure testing those portions of the project that can be done in advance. The contractor reviews the shutdown valving plan and details the installation plan including the brazing process. He then briefs his installers on the plan and prepares all tools and equipment required during the installation.

Communications Key

The shutdown process begins at the prearranged time only after all supervisors are notified the construction crew is ready, a credentialed Medical Gas System Certifier is present, and adequate alternate gas sources are in position. Communication by radio is essential to coordinate the shutdown process. First, the alternate gas supplies are activated and checked to see that they are capable of supplying the gas needs of all patients affected by the shutdown. These alternate gas supplies are closely monitored throughout the shutdown process and replaced as they become depleted. Once it is verified that patients are adequately supplied from the alternate gas supplies, valves upstream and downstream from the area undergoing modification are closed to isolate the construction zone. These valves should be located by the contractor in advance of the shutdown. With valve closure, the construction crew begins work on the pipeline. Components of the planned modifications are cleaned carefully, then assembled. Prior to brazing, the pipeline is purged with an inert gas, usually nitrogen, until all oxygen is removed. This prevents the formation of copper oxide scale inside the pipeline during the brazing process.

After brazing is completed, the isolated construction zone undergoes pressure testing. If no leaks are found, the nitrogen in the pipeline is then purged using backflow from branch lines (sequentially) and/or the primary source until completely removed from the pipeline system. The primary source is left on-line, and the final stage of the shutdown process recertification begins.

Recertification involves purity and crossover testing of all outlets in the construction and immediately adjacent zones. An independent, credentialed Medical Gas System Certifier should perform these tests and document that each process and procedure of the shutdown was performed correctly. If problems are detected during testing, the installers remain available to correct system flaws or replace malfunctioning pipeline components. As zones are recertified after purity testing, patients are switched from the alternate sources back to the primary gas pipeline system. Upon completion of the recertification testing, all equipment is removed, and all parties the contractor, the institution, and the Certifier must prepare reports on the shutdown.

Thus, the process of shutting down the MGPS is a complex task that potentially exposes patients to greater risks. Good communication and close cooperation between the contractor and institution personnel help to minimize the risks to patients. Uninterrupted medical gas service to patients is a requirement in any shutdown. The anesthesia team needs to understand the MGPS and become an active participant in any shutdown process to maximize safety for their patients.

Guidelines for Planned Medical Gas System Shutdown

Project Definition and Preparation: The goal is to produce a comprehensive written plan of action, and make preparations for the shutdown.

1. Define scope of project. (Institution)

2. Obtain up-to-date plans of the MGPS as actually constructed. (Institution)

3. Determine the areas of the MGPS that will require shutdown. (Contractor)

4. Estimate duration of the required shutdown. (Contractor)

5. Notify affected areas of proposed shutdown. (Institution)

6. Meeting of affected services and contractor to:

a. Set date and time for shutdown. (Joint)

b. Choose method for alternate gas supply. (Joint)

c. Determine equipment and gas supply needs. (Joint)

7. Order equipment and gas supplies. (Either)

8. Coordinate and train staff for shutdown procedure. (Institution)

9. Define and order components for MGPS modification. (Contractor)

10. Prefabricate and pressure test all component assemblies that can be done in advance. (Contractor)

11. Define assembly procedure and preparation process for brazing. (Contractor)

12. Organize and brief installers on plan and policies. (Contractor)

13. Prepare necessary tools, equipment, and material. (Contractor)

14. Arrange for Medical Gas System Certifier. (Joing)

15. Pre-shutdown modifications to MGPS (inlets). (Contractor)

Shutdown Procedure: The goals are a smooth, uninterrupted transition to alternate gas supplies for all patients affected by the shutdown, along with efficient modification to the MGPS.

1. Notify supervisors in all affected areas of the planned shutdown. (Institution)

2. Distribute alternate gas sources and necessary equipment. (Either)

3. Close zone valves and transfer to alternate gas supplies. (Institution)

4. Assure all patients are provided for throughout the procedure. (Institution)

5. Commence shutdown of primary supply. Notify installers. (institution)

6. Vent system gas and purge with nitrogen. (Contractor)

7. Perform planned modifications, assemble components. (Contractor)

8. Purge assembly until 02 Content 0% (Contractor)

9. Verify contents of piping assembly. (Certifier)

10. Braze joints. (Contractor)

11. Pressure test system when done. (Certifier)

12. Vent nitrogen out of system, flush out with primary source and/or backflow from branch lines. (Contractor)

13. Put primary supply back on-he. (Institution)

14. Notify supervisors that construction is completed. (institution)

Recertification: The goals are rapid purity checking to detect system flaws, correct them, and transition patients back to the primary supply.

1. Purity checking of outlets in zones affected by the shutdown. (Certifier)

2. If flaws or other component problems are detected, repair. (Contractor)

3. Return zones to main supply if purity checks OK. (Institution)

4. Discontinue alternate sources, remove equipment for return. (Institution)

5. Remove construction equipment, debris, tools. (Contractor)

6. Reports of shutdown procedure including purity checks. (All three)

7. File copies of summary report and purity checks. (Contractor)

Dr. Peterson is Assistant Clinical Professor of Anesthesiology at the University of Arizona, Phoenix campus, and Dr. Evans is President of Medical Gas Management, Inc., Bethany, Oklahoma. Both are members of the APSF Subcommittee on Medical Gas Vacuum Systems.


1. Feely TW, Hedley-Whyte J: Bulk oxygen and nitrous oxide delivery systems: design and dangers, Anesthesiolog 44:301-305,1976.

2. Moss E. APSF Subcommittee on Medical Gas Systems, April 4,1994 Meeting agenda.

3. Wentling DG. Important Considerations Prior to Hospital Shutdown. BOC Healthcare Memo.