Daily, in hospitals throughout our country and increasingly throughout the world, hospital patients depend on the assistance of various hospital plumbing systems for their recovery from illnesses. The range of hospital plumbing has expanded from conventional sanitation and potable water systems to include assistance in medical procedures and total life support.

This evolution is being demanded of the plumbing and the health care industries by forces that apply to both industries: patient and doctor insistence on technically superior products and services, new codes and standards, and serious economics.

The centrally-piped medical gas system is one of the newer types of hospital plumbing systems to be introduced into the delivery of direct patient care. Gas piping is needed for oxygen, nitrous oxide, medical air, nitrogen, carbon dioxide, vacuum and anesthesia waste exhaust. Piping gas from a central location directly to outlets at the points of patient use provides a level of safety unheard of in the past. The direct piping method removes obsolete, bulky and dangerous pressurized cylinders from the patient's bedside. Also, these piped systems provide easier quality control and pressure regulation because all gases are delivered from centralized pumps, compressors or cylinder manifold systems. The piping is designed and installed under strict National Fire Protection Association regulations (NFPA 99).

Medical gas installations have effectively placed hospital plumbing professionals directly into the loop of patient care. To guarantee patient safety, they must become knowledgeable about exactly how each of these systems effects the total care of the patient-just as the hospital's medical staff must.

Introducing Human Factors

It is remarkable that there have been extremely few reported accidents or deaths resulting from the utilization of life-supporting medical gas systems during their rapid period of growth and improvements. Responsibility for this outstanding record (although even one accident must be considered unacceptable) I credit to the dedicated professionals who periodically introduce more rigorous performance standards, formalize installation and maintenance procedures, continually improve the design and manufacturing techniques of increasingly reliable tangible equipment, and install and inspect these systems.

Our challenge for today and the future, however, must be to reduce this minuscule accident rate to zero, while our population, medical gas usage and future unknown medical gas requirements continue to increase exponentially. Without this zero-accident goal, the long-term trend of expansion is paving the way for an intolerable number of accidents, even if our already enviable accident rate remains the same.

With our future unlikely to yield the numerous technological advances that improved the safety of medical gas systems in the past, this task will be enormous. To achieve our zero-accident goal, we must concentrate on improving the human factors of medical gas systems.

What are human factors, how do they affect the safety and performance of medical gas systems and where do opportunities for improvement exist?

The term "human factors" refers to the determination of our human nature, especially in our modern technical society, to improve our quality of life tremendously-but then to become complacent. For example:

  • We have the grand vision to invent an incredible machine like the computer and integrate it as a manager into a life-critical medical system. However, we then may be inclined to become complacent and let the computer "run the show," while we allow ourselves to become distracted and shift our attention to a new challenge.

  • Our grand vision becomes tunnel vision when we choose not to interact with other related professional groups to share information that, if our expertise were to combine with theirs, would tremendously improve the lives of everyone.

The chief positive context of human factors, however, is the insatiable desire of we human beings to continually improve our quality of life, and the creativeness and ability-when properly motivated-to join forces to make it happen.

The downside of our human nature is evident in the problems that we often cause ourselves and others. The positive side of our nature is evident in our ability to prevent or resolve these problems.

Latent Failures

Latent failures are questionable practices or situations that provide the catalysts that could potentially cause a catastrophic event. They are tied to decisions that may not yet have visible consequences. Although an obvious mechanical or work-practice failure may cause a life-threatening situation, the root cause may be habitually poor system design practices, operating procedures, maintenance procedures or communications between those involved in the installation and maintenance of the associated hospital plumbing system. Because they could trigger that "one-in-a-million" catastrophic accident, latent failures must be identified, eliminated where possible or managed where necessary. Here are some examples of identified potential or real-life latent failure events.

Condensation in gas lines. Plumbing engineers who design medical air lines for use in northern climates may route them through building areas that periodically have very cold temperatures. Because there are no published guidelines for this situation, the engineers fail to realize that this may result in dew point problems. Rarely, medical air can accumulate enough condensation as it passes through the very cold areas to slowly contaminate piping and ventilator filters. There may be no visible consequences through years of use of any of these northern climate medical air systems designed this way, but one day, one of them may finally cause a life-threatening contamination problem in an intensive care unit.

If a formal national committee existed, one that could accept and act upon a report of any hospital that encountered this problem, a directive could be written and forwarded to hospital plumbing engineering organizations urging their vigilance for this design condition.

Inadequate budget. Hospital plumbers in one case found that internal parts of medical air wall outlets were beginning to corrode, and respiratory therapy reported damp and semi-clogged filters in its ventilators. The plumbers and respiratory therapy reported the problems to hospital engineering, who discovered that the driers were in need of either total renovation, or because of a recent construction expansion, extensive upgrading. Unfortunately, there was no money in the present budget, so temporary measures were taken to help, but not solve the problem.

Although this particular latent failure was basically an ignored recognized hazard, luckily it did not cause a major accident because the hospital eventually upgraded its medical air dryer system. However, the existence of mandated-and enforced-periodic medical gas system quality control re-certification regulations could have prevented this latent failure from occurring.

CAD over-dependency. From discussions with engineers, I have found that abusive reliance on CAD systems is becoming a major concern. I call this "automation dependency." An example of this occurred in medical vacuum lines of a surgical suite. An engineer, unknowledgeable in medical gas installations, totally relied on a CAD system to design a medical vacuum system. The engineer didn't consult coordinated drawings, so the system looked adequate on the blue prints. However, during the installation, the installing plumbers had to add changes of direction and elevations. This made the CAD-designed pipe sizes inadequate. The engineer never field-verified the actual installation for engineering accuracy. Five years later, a surgical patient faced a life-threatening situation because his individual operating room's suction system was clogged with dried accumulations in the piping system. Inspection of other medical vacuum lines of the same surgical floor revealed that other pipes were also slowly becoming clogged with accumulations.

A knowledgeable national committee could create a guideline suggesting appropriate use of CAD software for design by hospital plumbing engineers. It could also furnish a system for engineering firms to confirm that every phase, both technical and procedural, of their CAD automation operations is continually functioning properly. Also, a legally-mandated, periodic medical gas system re-certification and quality control program could have aided the hospital in discovering the slowly accumulating results of this latent failure before the life-threatening event. The surgery vacuum outlets, even though they would pass the minimum static 12-in. Hg test, would have begun to indicate an eventual failure of the minimum 3 scfm test that alerts that the lines are beginning to clog.

Failure to purge. Another example of poor practice is the unawareness of the installing plumbers of the need to use a nitrogen purge while silver-brazing pipe fitting joints. This lack of purging allows copper oxide particles to form on the piping walls that could break loose and either be directly breathed by the patient, clog ventilator filters or actually corrode aluminum parts of the ventilators.

The existence of permit and periodic inspection requirements by governmental agencies regarding installation of medical gas systems, such as those that presently exist for plumbing systems providing sanitation, would guarantee that all the life-critical systems are purged during brazing. Also, the design engineer should have specified that the plumbing contractor's plumbers be certified not only in the brazing of copper joints, which is all that NFPA 99 requires, but that they also possess an extensive knowledge of all other medical gas system design demands as well. Another check would have been the hospital investing funds to certify its own plumbers in medical gas installation. These plumbers would have observed that the contractor's plumbers were not using proper installation procedures and stopped their work.

Poor communications and practice. Hospital plumbing crews routinely perform multiple-gas tie-in service interruptions for renovation projects. Because there is no standardized medical gas service interruption procedure available to guide them, and they are usually in the "hurry-up syndrome," they always simultaneously relieve pressure from all the medical gas lines, cut in the branch tees and turn the lines back on. Because there are no visible consequences to this procedure-as of yet-it constitutes a latent failure.

Because this habit bypasses an error-management technique that serves as a critical safety check in pipeline identification, it is actually a life-threatening practice. For a simultaneous multi-gas tie-in shutdown-such as oxygen, air and nitrous oxide-to be performed safely, only one gas at a time should be shut down, the pipeline's pressure bled and the line punctured. If the punctured pipe is not pressurized, the plumbers will be positive that the pipe was identified correctly. If the pipe is still pressurized, the plumbers will immediately realize that they made a serious identification error.

In this example, because only one line was shut down, this immediately discovered error remains an individual discipline's error, and the plumbers can manage and correct it immediately. If all the misidentified lines were shutdown simultaneously, tied into and turned back on, the plumbers would have unknowingly crossed the lines, and their individual error would now become a team error. The latent accident would become a real accident, and the potential catastrophe resulting from an anesthetized patient breathing N2O or medical air from his marked and indexed oxygen outlet moves one step closer to reality. It is now up to the verifier, the next member of the team, to identify the mistake. If the verifier has also had a bad day, the error advances to the anesthesiologist to identify.

A formal medical gas service interruption procedure needs to be published that discourages the practice of simultaneous interruption. This procedure would assist the plumbing crew in avoiding the incident of turning these lines back onand discovering that they had actually crossed different types of medical gas pipes.

Uncertified practitioners. Uncertified hospital plumbers allowed a contractor to use uncertified plumbers to routinely renovate downstream of multiple live zone valves. They were all aware of the need for the nitrogen test on the gas piping, but instead of disconnecting the lines from the live zone valves before renovation and testing, they placed 150 psi of nitrogen against all of the live zone valves. These plumbers routinely caused this latent failure at other hospitals, fortunately with no visible consequences there either. On any occasion, however, an oxygen zone valve could have leaked, and nitrogen could have been introduced into a live oxygen piping system from which patients were breathing!

If an approved, published medical gas service interruption procedure existed with a directive prohibiting testing against live zone valves, this latent failure might never occur. Also, if it was a law that medical gas systems must be installed by certified plumbers and the pressure testing of these systems be witnessed by a government-certified inspector of record, this situation would never occur. Finally, if the design engineer and the hospital itself specified that any medical gas installation be performed by only certified plumbers, this serious latent failure would be eliminated.

Inadequate preventive maintenance. Hospital plumbing crews routinely ignore manufacturers' preventive maintenance recommendations regarding automatic changeover manifolds. With the extensive redundancies built into these systems, these manifolds give the perception of being capable of "running themselves" for years, even while detectable anomalies are ignored-with no visible consequences. In one case, the primary line pressure regulator of a surgical nitrous oxide manifold failed, and the system was switched over to the redundant regulator. After months of ignoring the repair needs of the primary regulator, the redundant line pressure regulator also failed, and there was a massive nitrous oxide failure during surgery.

Renovation. One major latent failure worthy of extended discussion is the link between our nation's managed care system and hospital renovations. Unlike the old, noncompetitive fee-for-service reimbursement system, the managed care system is a competitive system that pits every hospital against each other to maintain its customer (patient) base. Hospitals must now bid against other hospitals, just like contractors do in the construction industry, for managed care contracts-and their multitude of patients.

This system has created a very competitive health care delivery atmosphere, with many hospitals joining forces against others to deliver unique and better services to retain its present patients and attract new ones.

To provide these enhanced services, most hospitals are undertaking renovation projects. Some of these are added structures, but most are smaller, very complex renovation projects in existing buildings. These renovation projects usually require alterations to the medical gas system, which leads to temporary service interruptions of each medical gas. The interruption of medical gases presents the most serious challenge to the hospital plumbers.

To remain alive, many patients in intensive care, in surgery, or on the floors require the use of a continuous source of piped oxygen, medical air or wall suction. During these critical medical gas interruptions, it is the hospital plumbers who have the direct, hands-on responsibility of temporarily supplying these life-supporting medical gases directly to the patients. They must also supervise or actually perform the pipe work, and when the pipe work is complete, guarantee the verification of the integrity of all aspects of the system.

Each service interruption performed, because of its potentially fatal consequences to the patients, must be taken very seriously. To avoid becoming complacent or careless, the plumbers must commit to executing each interruption as cautiously as their first one. Each interruption can be unique, and the plumbers must be very creative to plan far in advance every procedure and piece of equipment that will be needed. Sometimes the renovation requires only the relocation of wall outlets in an unoccupied, single room. In this case, only a zone valve may need to be shut off and the outlets relocated and re-certified according to code. Other times, an entire riser must be shut down. This will require the isolation of, and the supply of temporary services to each zone on the riser. To provide temporary oxygen or medical air, one can use a simple two "H" cylinder manifold system that will feed an entire zone. This system allows each zone valve on the riser to be shut off and the entire zone to be back-fed through one or two wall outlets in the zone-usually at an empty bed space. When the zone valve is shut off, this system provides normal service to each wall outlet with no disruption to patient care. Also, this method eliminates the need for nursing or respiratory therapy to spend time attaching each patient to individual oxygen cylinders.

There are times when an entire wing must be shut down. This, depending on the wing's piping and valve configuration, may require that temporary service be supplied to most or all of the building. In the case of oxygen, it is possible to feed oxygen into the building's emergency inlet from a truck. This method makes the shutdown simpler, but it requires considerable lead time to be arranged.

When performing renovations that require service interruptions, hospitals are presently relying on their own ingenuity or word-of-mouth advice from other hospitals. This is because there are no nationally approved medical gas service interruption procedures and because some hospitals neither employ medical gas certified plumbers nor hire plumbing contractors with certified plumbers.

These numerous renovation projects, some with very accelerated completion dates that encourage a hurry-up attitude when performing medical gas service interruptions, are prime sources of latent failures. These are potential problems that should be addressed immediately. Again, the creation and publishing of a single, nationally approved medical gas service interruption manual would be a priceless safety aid that would help to prevent a serious mishap that could result in patient fatalities.


Progress is already being made in coordinating and guiding the activities of those working on hospital plumbing systems. Activities that treat different segments of medical gas systems are occurring at state and local levels across a wide spectrum of organizations and institutions.

Inspection. Presently there are no nationally standardized inspection procedures universally recognized among the states. However Alabama, California, Colorado, Florida, Georgia, Kentucky, Louisiana, Montana, New Mexico, Oregon, Tennessee, Texas and Washington have varying permit-driven medical gas inspections requiring installation by certified medical gas installers and inspection by the state's own certified inspectors. As of this writing, other states have acknowledged the necessity of these inspections and are beginning inspection programs with their own inspectors of record.

Accreditation. The two original and major accreditation agencies in the country that pioneered training and certifying of individuals in medical gas installation, inspection, verification and maintenance are National ITC Corp. (NITC) of Los Angeles, CA, and American Medical Gas Institute (AMGI) of Metairie, LA.

Training. The United Association has challenged its local unions to become very progressive in teaching its members proper installation according to NFPA 99, using NITC and AMGI teaching methods. A local that has taken this challenge very seriously is Plumbers' Local 55 in Cleveland, OH. At its apprentice training/journeyman re-training facility, the members, in conjunction with the Cleveland Plumbing Contractors' Association, have finished the construction of The Cleveland Medical Gas Training Center. All training meets the requirements of NFPA 99, NITC and AMGI. This very impressive facility consists of four main components:

-A large classroom with audio-visual and computer services.

-A mini-hospital totally piped with functional medical gas. It is completely furnished with beds and medical equipment that also includes a nurses' station, patient rooms, an emergency room and a medical gas supply room .

-Twelve brazing stations for proper hands-on training in medical gas line brazing.

-Four offices and a conference room.

Professional organizations are also making great strides in teaching proper medical gas installation techniques.

New standards. While NFPA 99, Health Care Facilities, covers the general field of medical gas and vacuum systems, it does not specifically address requirements in these areas that would allow an individual to be certified as a qualified installer, inspector or verifier. To cover these areas, the American Society of Sanitary Engineering has completed a standards series written in accordance with procedures developed by the American National Standards Institute (ANSI). ASSE/ANSI Series 6000, Professional Qualifications Standard for Medical Gas Systems Installers, Inspectors and Verifiers was released in April 1998. The standard is currently in revision to include requirements and recommended procedures for medical gas service interruptions, maintenance procedures and instructor training. The anticipated release date of the revision is the beginning of 2001.

The ASSE/ANSI Series 6000 qualifications standards are based on the requirements of NFPA 99, 1999 edition, for both Level 1 systems (hospitals, ambulatory care centers, clinics and nursing homes), and Level 2, 3 and 4 systems (typically limited-care nursing homes, limited-care facilities, dental offices and laboratories).


Because the problems described earlier reflect only my own conversations with engineers and my peers at other hospitals about concerns and real events, they must touch just the tip of the iceberg of a multitude of latent failures. This emphasizes that in many medical gas system installations and operations, there must be numerous types of latent failures occurring daily in our hospitals that have yet to present visible consequences.

However, at any time, combined with the perfect set of circumstances, any one of these seemingly benign latent failures being performed repeatedly throughout the country could start a chain of reactions that transforms it into the root cause of a major accident.

The progress that has been made so far is remarkable, but intense collaborative efforts of all medical gas professionals on a formal, multi-disciplinary, resource management-type committee are needed to make systematic, long-lasting progress towards our zero-accident goal. The committee would be chartered to guide development, implementation and enforcement of seamless codes, standards and procedures. It would implement policy where it can and develop plans to coordinate with government where it can't act independently. The committee would include individuals from all professional groups affiliated with medical gas systems, including:

  • Regulating bodies who write standards and codes for the actual performance, design, and installation of the tangible components.

  • Plumbing engineers who competently design each individual system.

  • Plumbing contractors and certified plumbers who install the systems.

  • Medical equipment manufacturers.

  • Governmental inspectors of record who witness the installation and pressure testing, and certify the integrity and identification markings of the roughed-in piping system.

  • Verifiers who not only confirm and certify that the installed system (including every tangible component except the piping) is installed and alarmed correctly but also verify that each individual wall outlet delivers the correct type, concentration, quality and quantity of medical gas.

  • Hospital facilities engineering departments which, using industry-accepted maintenance and renovation procedures, must guarantee the integrity of the entire system throughout its life.

  • Progressive representatives of the professional medical community.

  • Medical gas manufacturing companies.

  • Accreditation agencies, trade unions and professional organizations that teach installation and testing principles to the installing plumbers, piping inspectors, verifiers and facilities' engineering plumbers.

The committee should set a goal of total commitment to establish the following programs to identify and act upon reported risks in the human factors of medical gas operations. These risks affecting medical gas safety could then be successfully eliminated when possible, or managed when necessary, through proactive programs directed at identifying and dealing with deficiencies such as those described. Programs could include:

Reporting programs. A formal reporting system should be implemented that provides a path that any concerned and inquisitive hospital plumbing professional can follow without retribution (anonymously, if necessary) to report latent failures of operations to the committee. If properly investigated, these inconsequential failures would become primary sources to identify and eliminate or manage weaknesses that could cause eventual consequential failures. The committee would have national influence in identifying areas of improvement and recommending solutions to eliminate or manage these latent-failure practices on a national level. These actions would take forms from simple directives, such as recommending increased training or equipment to implementing nationally standardized design, installation, inspection, verifying, maintenance and service interruption procedures as lawful regulations.

Lobbying programs. Formal international lobbying programs should be started to educate and influence states and municipalities on the importance of establishing legal permit requisition and inspection programs regarding medical gas systems.

Publicity programs. Publicity programs encouraging a health care system-wide safety culture regarding improvement and coordination of human factors related to medical gas system installation and maintenance are essential in providing the incentive for medical gas safety improvements into the far future.