6.4 Medical-Surgical Vacuum, WAGD & Medical Support Gas Sources
Key Takeaways
Category 1 vacuum sources need two or more pumps that serve peak calculated demand with the largest pump out of service, plus a receiver and backflow prevention.
Vacuum systems other than liquid ring must have at least duplex inlet filtration on the patient side, at least 99.97% efficient at 0.3 micron (HEPA), sized for 100% of peak demand with one filter isolated.
Vacuum exhausts must be outdoors, at least 25 ft from doors, windows, air intakes, and other openings, at a different level from air intakes, and free of dips and loops or provided with a drip leg.
Pumps dedicated to WAGD must use materials, lubricants, and sealants that are inert to oxygen, nitrous oxide, and halogenated anesthetics.
Instrument air dew point alarms activate above -22°F (-30°C), and an instrument air standby header holds enough cylinders for 1 hour of normal operation.
Medical-Surgical Vacuum: Uses and Limits
Medical-surgical vacuum provides drainage, aspiration, and suction to remove body fluids from patients. The facility may not use the medical-surgical vacuum or WAGD system for nonmedical applications, such as steam condensate return.
Vacuum Central Supply Requirements (Category 1)
| Component | Requirement |
|---|---|
| Pumps | Two or more, enough to serve peak calculated demand with the largest pump out of service |
| Backflow | Automatic means to prevent backflow from on-cycle pumps through off-cycle pumps |
| Isolation | A shutoff valve or other means to isolate each pump without losing vacuum in the system |
| Receiver | ASME Section VIII; able to withstand 60 psi gauge and 30 in. HgV; manual drain; sized for the pump technology; serviceable without shutting down the system |
| Pump mounting | Materials the manufacturer deems suitable; antivibration mountings; flexible connectors to intake and outlet piping; liquid ring seal water of the quality the manufacturer recommends |
| Piping at the source | Per the vacuum piping rules. Brass, galvanized, or black steel may be used between the pumps, discharges, receiver, and source valve as the manufacturer recommends. |
| Arrangement | Service and continuous vacuum through a single fault |
| Source valve | Required, per the valve rules |
| Lab connection | Where one set of pumps also serves an analysis, research, or teaching lab, the lab connects separately at the receiver through its own isolation valve and fluid trap. A scrubber may be installed between them. |
Inlet filtration (vacuum sources other than liquid ring)
- At least duplex, so one filter can be changed without affecting the vacuum system
- On the patient side of the vacuum producer
- At least 99.97% efficient at 0.3 micron (HEPA)
- Sized for 100% of peak calculated demand with one filter or filter bundle isolated
- Isolation valves on both sides of each filter or bundle
- A way to see any accumulated liquid
- A vacuum relief petcock to relieve vacuum in the canister before the filter is changed
- In normal operation, one filter or bundle is isolated as a standby
Vacuum Exhaust
The exhaust must keep noise and contaminated discharge away from people and air intakes:
| Rule | Requirement |
|---|---|
| Location | Outdoors |
| Separation | At least 25 ft (7.6 m) from any door, window, air intake, or other building opening, and from places of public assembly |
| Level | At a different level from air intakes |
| Dispersion | Placed so prevailing winds, nearby buildings, topography, and similar factors will not push exhaust into occupied areas or block dispersion |
| End treatment | Turned down and screened with noncorroding screen |
| Drainage | No dips or loops that could trap condensate or oil, or else a drip leg with a valved drain at the low point |
| Multiple pumps | A common exhaust is allowed if sized for back pressure per the manufacturer and each pump can be isolated |
Compare this with the medical air intake, which must be at least 25 ft from vacuum and WAGD discharges. Locating the vacuum exhaust and medical air intake properly is one of the most consequential layout decisions on a job.
WAGD
WAGD captures and removes gases vented from the patient breathing circuit during normal operation of anesthesia or analgesia equipment. WAGD producers are dedicated to that service.
- Pumps dedicated to WAGD must meet the vacuum pump requirements, and they must be built with materials, lubricants, and sealants that are inert to oxygen, nitrous oxide, and halogenated anesthetics. Exhaust from anesthesia circuits can be oxygen-rich.
- Low-vacuum producers such as fans or blowers designed for vacuum below 5 in. HgV may use materials the manufacturer deems suitable. They must have antivibration mountings and flexible connections, be used only for WAGD, and be connected by piping or ductwork suited to the service.
- Where WAGD is produced by the medical-surgical vacuum source, that source must meet the vacuum source rules and be sized for the added volume. NFPA 99 also limits or monitors oxygen concentration in the combined system.
- WAGD inlets are not interchangeable with vacuum inlets. Master alarms carry a WAGD low signal, and local alarms show low WAGD reserve capacity.
Medical Support Gases: Nitrogen and Instrument Air
Nitrogen NF and instrument air power equipment used in patient care procedures. Medical support gas systems must not carry oxidizing gases other than air, or gases meant for breathing. They may be piped to areas with a support purpose and, where appropriate, to laboratories.
| Topic | Requirement |
|---|---|
| Standard pressure | 160-185 psi is the standard range for valve and outlet labeling; other pressures must be labeled |
| Outlet performance (verifier test) | 5.0 SCFM (140 SLPM) with no more than a 5 psi drop, at a static pressure of 160-185 psi |
| Instrument air dew point alarm | Above -22°F (-30°C) at line pressure, local and master |
| Instrument air reserve capacity | Local alarm when a multi-compressor source could not handle demand if one compressor stopped |
| Instrument air standby header | Cylinders for 1 hour of normal operation; CGA V-1 medical air connectors; enters upstream of the final line filters; serves automatically if the compressor fails |
| Cylinder storage | Instrument air reserve cylinders may share a room with an instrument air compressor if it is the only machinery in the room |
| Outlets | Above 80 psi, DISS or an adapter-retaining design |
Category 2 and 3 Vacuum
Category 2 and Category 3 medical-surgical vacuum systems may be simplex if facility staff have an emergency plan for losing vacuum. Category 3 systems also need emergency electrical service per NFPA 99 Section 6.6 and NFPA 70.
Testing Tie-Ins
- The installer's 24-hour standing vacuum test holds between 12 in. HgV and full vacuum (Section 7.2).
- The verifier confirms each vacuum inlet can draw 3 SCFM while an adjacent inlet stays at or above 12 in. HgV (Section 7.4).
- Before use, the verifier tests that the vacuum source system functions properly.
How far must a medical-surgical vacuum exhaust be from doors, windows, air intakes, and other building openings?
At least 10 ft
At least 25 ft
At least 20 ft above grade, with no horizontal distance rule
At least 50 ft
A vacuum plant uses rotary vane pumps, not liquid ring. What inlet filtration does NFPA 99 require?
A single 5-micron filter on the exhaust side
No filtration, because rotary vane pumps are self-cleaning
Duplex filters on the exhaust side of the pumps, rated 95% efficient at 1 micron
At least duplex, patient side, HEPA (99.97% at 0.3 micron), sized for peak with one isolated
How much cylinder capacity must an instrument air standby header provide?
Enough for 1 hour of normal operation
Enough for one average day's supply
Enough for 24 hours of normal operation
At least three cylinder connections, regardless of demand
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