What You Need to Know About Medical Gas System Design - By Eric Sellers PE, CPD

Medical gas systems in healthcare facilities typically include oxygen, medical air, carbon dioxide, nitrogen, nitrous oxide, medical vacuum and waste anesthesia gas disposal systems. Few systems are more critical to a facility’s operations and to patient care than these systems. Maintenance problems and shut-downs in these systems can jeopardize a facility’s ability to provide services and can increase risk to patient safety. A well prepared medical gas design can minimize the potential for these risks.

Source Equipment

Medical air compressors, medical vacuum pumps, high pressure gas manifolds, and bulk liquid cryogenic storage tanks are the heart of medical gas systems. When selecting medical gas source equipment it is important to consider anticipated growth and expansion of the facility to avoid costly upgrades. In addition to building expansions, clinical advancements may also lead to changes in demand and usage of certain medical gases. However, when preparing for future growth, keep in mind that bigger is not always better. Oversized pumps or compressors can lead to frequent cycling which can reduce the expected useful life of the equipment.

Because of the significant role medical gas systems play in a healthcare facility, redundancy and emergency power must be provided for each piece of source equipment. Redundancy is provided for medical air compressors and medical vacuum pumps through the use of duplex, triplex or quad systems. Multiplex systems allow for optimum operating efficiency at a broad range of flow rates; this can lead to decreased energy usage and operating costs. A properly designed multiplex system also allows for portions of the system to be maintained, replaced and expanded without a complete shut-down.

In large healthcare facilities, medical air compressors; medical vacuum pumps and medical gas manifolds such as nitrogen, nitrous oxide and carbon dioxide are typically located inside the building. A bulk liquid oxygen storage system is usually provided on site at a location which allows for delivery of the liquid oxygen by a large tanker truck. Medical gas manifolds should be located in a dedicated room with adequate ventilation and storage space for empty and replacement cylinders. National Fire Protection Association’s NFPA 99 – Standard for Healthcare Facilities does not permit manifolds to be located in the same room as compressors, pumps, boilers, mechanical equipment or other potential sources of ignition. Medical air compressors and vacuum pumps are allowed to be located in a common mechanical room with the building’s other mechanical equipment.

Another important item to consider when planning for the installation of source equipment is the location of the intake for medical air compressors. Contaminated air can enter the medical air system through the intake piping if it is located too close to HVAC exhaust, flues, vacuum exhaust, plumbing vents and vehicular exhaust. Likewise, it is important to not terminate vacuum exhaust near fresh air intakes for the building or near occupied areas.

Monitoring and Alarm Systems

All medical gas systems must be monitored. NFPA 99 requires that master alarms (monitoring for source equipment) be provided in at least two locations inside of Level 1 healthcare facilities. A Level 1 facility is defined as any facility where the interruption of the medical gas system would place patients in imminent danger of morbidity or mortality. One master alarm panel must be located in the maintenance shop, engineering department or work space of the individual responsible for maintaining the medical gas and vacuum systems. The second master alarm panel must be in a location that will provide continuous observation. Acceptable locations for a second master alarm include the telephone switchboard, security office, reception desk, emergency department nurse station or other locations that are continuously staffed.

In addition to the master medical gas alarm panels, area alarms are required for all anesthetizing locations and other vital life support and critical care areas (post anesthesia recovery, intensive care units, emergency departments, etc.) In addition, area alarms should be provided for any area where a loss of the medical gas system, without immediate intervention by the staff, would negatively affect the patient’s health and safety. Area alarm panels must be located at the nurses’ station for the area they serve, or a similar staffed location.

Area alarms monitor the medical gas systems through sensors located on the patient side of the zone valve box serving the area. An exception to this rule is that sensors may be located on the source side of zone valve boxes which serve anesthetizing locations. For example, sensors may be located on a single branch line that serves multiple operating rooms in the same suite. In this case, the alarm panel would be located at a staffed location that oversees the entire suite.

Piping Systems

The design and layout of the medical gas piping system should minimize pipe lengths, provide for ease of maintenance and repair and allow for future expansion. Minimizing pipe lengths decreases pressure loss in the system and also decreases installation costs. Oxygen cleaned copper piping with brazed joints must be used for medical gas and vacuum systems. Due to the high cost of copper and the labor intensive process of brazing, costs of these piping systems can be increased significantly if not designed properly.

Appropriately placed valves are the best way to allow for maintenance, repair and expansion of the piping systems while avoiding disruption to a large portion of the facility. Valves are required by NFPA 99 at the source, on the main supply line, on all risers at the take-off from the main line, and on each floor at the take-off from the risers. Optional in-line service valves and valves for future connections should also be provided to aid in repair and expansion of the systems. These required and recommended valves must be located such that they are only accessible to authorized maintenance personnel, and in some cases, must be locked in the open position.

By contrast, zone valve for use by all medical staff must be accessible from the standing position, located in corridors in plain view; not hidden behind closed or open doors. All points of use in the medical gas and vacuum system must be separated from the source equipment by a zone valve box. Zone valve boxes should be provided for each department or function in the facility. These valves must be located on the same floor and separated by a wall from the outlets they serve. It is also required that a pressure/vacuum gage be installed on the patient side of zone valves.

Outlets

Locations and quantities of outlets should be carefully coordinated with the facility’s staff. The AIA Guidelines for Design and Construction of Health Care Facilities outlines minimum quantities for outlets for various functions in a healthcare facility; however, additional outlets may be used depending on the type of care the facility provides.

Outlet locations should also be provided such that they are easily accessible to the medical staff with limited disruption to the patient and procedures. Depending on the use of the room, ceiling, boom or wall mounted outlets may be used.

Conclusion

The medical gas systems are one of the most crucial systems to a healthcare facility’s operation. Medical professionals rely on these systems to perform numerous procedures and to ensure their patients’ well being. Including an experienced, licensed design professional in the design and, equipment selection process for new facilities as well as system upgrades can help ensure proper planning, installation, and maintenance of these essential systems.

For more information or questions about medical gas system design, please contact Eric P. Sellers, P.E., CPD, at 717-845-7654 or email at eps@ba-inc.com.