NFPA 99C: How It Affects the Biomedical Engineer—Part 2

The NFPA 99C publication helps prevent potential fires and explosions caused by medical gas equipment, allowing health care personnel to safely do their jobs.

The NFPA 99C publication covers the installation, performance, and maintenance of afacility’s medical gas and vacuum systems. Its primary purpose is to prevent fires and explosions caused by the vast array of piping, fittings, and supply equipment installed in your facility.

In Part 1 of this two-part series (published in the October issue), the first five most-overlooked problem areas when managing a medical gas piping system were covered. This article will review problems six to 10.

6) Surgical Suites’ Medical Vacuums
A minimum of 85 LPM must flow through any medical-vacuum outlet in your facility. However, when the operating room (OR) suites are running full cases, up to six medical-vacuum outlets can be used in each suite. This becomes a problem when full caseloads are using maximum surgical suction. Additionally, any medical-vacuum outlet piped into a surgical boom or an articulated arm is connected to the piping system by means of internal flexible tubing, which causes a 15% loss of flow at the outlet.

It is critical that both vacuum mains and the branch lines feeding each surgical suite be sized to allow 100% of the outlets to be used with a full 85 LPM at each outlet. A general rule of sizing is to provide a minimum of 11¼4-inch vacuum-zone valves outside each surgical suite and a minimum of a 2-inch main feeding the entire zone. However, large city hospitals should do the math necessary to calculate a 100% utilization of the medical-vacuum outlets with no more than a 5-inch HG pressure drop to the farthest outlets.

Other common medical-vacuum problems are caused by the type and size of the vacuum tubing that connects to the disposable canisters, blockage of internal filters, and leakage of external caps used on disposables.

7) Remodels/Renovations
When it comes to medical gas systems, it is critical to pay a premium (instead of a low bid), let the owner choose the equipment your facility installs, and hire a certified medical gas installer with a current license (6-month renewals) for all brazing work.

Examples of what can happen when you do not follow this advice include the following:

1. A plumber doing oxygen-piping work on the second floor of a hospital put his nitrogen purge onto a pipe in the basement and filled all existing first-floor intensive care unit (ICU) oxygen outlets with nitrogen. Luckily, that morning, the verifier/inspector suggested that the hospital engineering staff put patients on “E” cylinders of oxygen prior to the plumbing work.
2. A plumber nearly used argon gas in lieu of the required nitrogen (NF) gas for purging while brazing.
3. When a plumber attempted to tie into an existing medical-air line for an addition or remodel job, milky water came out of the new outlets due to not checking existing conditions before making the tie-in. Preventive maintenance had not been completed for 23 years on the air dryers. All medical air lines were red tagged for hot trisodium phosphate cleaning and drying by the inspector.
4. A plumber was contracted to replace a penthouse medical air compressor, but existing piping was tainted with rust and mold due to a water separator failure years prior. All medical air lines were red tagged for replacement by the inspector.
5. After a plumber finished his certified installation, an in-house team added some oxygen outlets in a solarium that were missed on the scope of the plans. The in-house team mistakenly connected into the nitrous oxide piping; several deaths were attributed to this mistake. A final certified verification for the in-house work was the critical, overlooked step in this tragic situation.

Other major and sometimes lethal situations that can occur during remodeling projects are:

• cross-connections of various medical gases;
• residual nitrogen pockets left in the oxygen system by installers;
• residual chemical solvents (prohibited) left in any pressure medical gas pipe or fitting by the installer;
• nonmaintained medical air-compressor systems or respiratory-care delivery equipment contaminated with mold, rust, and moisture; and
• contamination by hydrocarbons such as methane, hexane, and petroleum by-products while installing the medical gas piping system.

8) Mismatched or Incorrect Series Repair Parts
Over the decades, all of the major medical-gas outlet suppliers have changed names and identities, thus complicating the identification of the specific medical-gas outlet by faceplate, latching mechanism, and internal-valve body measurements. Correct identification of a specific medical-gas outlet is key in the selection of repair components.

Another hidden consideration is that the medical-gas outlet could have been previously converted to new internals at some point, which makes it a hybrid of parts that can only be identified after its faceplate is removed. This hybridization was commonplace in the 1980s to eliminate the need for repiping the entire unit within the wall and shutting down areas of the facility. Mismatched repair components could, for example, limit the distance the internal outlet valve can open when a flow meter or regulator is attached and restrict the potential flow of that outlet.

Another problem happening at the installation is the depth the rough-in box is mounted in the plaster wall. If tile or wall finishes were added, this overall distance would be too long for the standard internal components to operate, and longer custom valves would have to be ordered for this location.

9) NFPA 99C Compliance
In facilities with older wings built during the 1960s and ’70s, many systems do not comply with current NFPA standards. At the time of system shutdown for upgrades, an inventory of current codes and components must be analyzed to safely update these 35- to 45-year-old systems.

The following is a partial listing of piping and component regulations instituted since the mid-’70s:

• All globe-style valves are prohibited.
• Vacuum piping shall not be less than 7/8-inch outer diameter.
• Medical-gas piping (positive-pressure gases) shall not be less than 5¼8-inch outer diameter.
• All zone valves must have a pressure indicator gauge in the assembly.
• Vacuum piping must be zoned at all critical care locations.
• All medical-gas piping shall be labeled at 20-foot intervals and at least once above every room.
• Installers and inspectors/verifiers must be certified.
• All gauges and sensors on the main pipeline must be fitted with a gas-specific demand check fitting.
• Area alarms are required at emergency departments and all other critical care locations.
• All oxygen piping shall be hard-drawn seamless copper ASTM B 819 type L and be marked by the manufacturer.

10) Emergency Policies and Procedures
Finally, your facility should have an emergency plan for the following critical situations:

• Loss of water main to medical vacuum and air-compressor systems (if applicable).
• Loss of buried oxygen main into the building due to excavation work.
• Loss of or interruption in power to medical-vacuum pumps and medical air compressors.
• Building oxygen pressure up to 70 PSIG and rising.
• Building oxygen pressure reduced to 40 PSIG and falling.
• A failed or badly leaking medical-gas outlet in a busy ICU/CCU (and the zone cannot be shut down for repair).
• A basement biomedical shop adjacent to a mechanical room that has just seized an oil-filled vacuum system. The corridor is filled with thick smoke and oil-laden vapors.
• A basement biomedical shop adjacent to a medical gas-tank room in which a cryogenic pressure vessel of nitrogen or nitrous oxide has just ruptured. The breathing zone in the hallways is lowered to below 18% oxygen by volume. 24x7

Michael Cohen is director, Med Gas Co, Minneapolis, and an ASSE 6020 Certified Medical Gas Inspector and ASSE 6030 Certified Medical Gas Verifier.