Medical air shall be required to have the following characteristics:
- It shall be supplied from cylinders, bulk containers, or medical air compressor sources, or it shall be reconstituted from oxygen USP and oil-free, dry nitrogen NF.
- It shall meet the requirements of medical air USP.
- It shall have no detectable liquid hydrocarbons.
- It shall have less than 25 ppm gaseous hydrocarbons.
- It shall have equal to or less than 1mg/m3 (6.85 x 10-07 lb/yd3) of permanent particulates sized 1 micron or larger in the air at normal atmospheric pressure. [NFPA 99:188.8.131.52.1]
Medical air compressors shall be installed in a well-lit, ventilated, and clean location and shall be accessible. The location shall be provided with drainage facilities in accordance with this code. The medical air compressor area shall be located separately from medical gas cylinder system sources, and shall be readily accessible for maintenance.
Medical air compressors shall be sufficient to serve the peak calculated demand with the largest single compressor out of service. In no case shall there be fewer than two compressors. [NFPA 99:184.108.40.206.3.9(B)]
Medical air compressor systems shall consist of the following:
Components shall be arranged to allow service and a continuous supply of medical air in the event of a single fault failure.
Component arrangement shall be permitted to vary as required by the technology(ies) employed, provided that an equal level of operating redundancy and medical air quality is maintained. [NFPA 99:220.127.116.11.3.9(A)]
- Automatic means to prevent backflow from all on cycle compressors through all off-cycle compressors.
- Manual shutoff valve to isolate each compressor from the centrally piped system and from other compressors for maintenance or repair without loss of pressure in the system.
- Intake filter-muffler(s) of the dry type.
- Pressure relief valve(s) set at 50 percent above line pressure.
- Piping and components between the compressor and the source shutoff valve that do not contribute to contaminant levels.
- Except as defined in Section 1313.2.2(1) through Section 1313.2.2(6), materials and devices used between the medical air intake and the medical air source valve that are of any design or construction appropriate for the service as determined by the manufacturer. [NFPA 99:18.104.22.168.3.2 (2-7)]
Category 2 systems shall comply with Section 1313.0, except as follows:
- Medical air compressors, dryers, aftercoolers, filters, and regulators shall be permitted to be simplex.
- The facility staff shall develop their emergency plan to deal with the loss of medical air. [NFPA 99:22.214.171.124]
Category 3 dental air compressor supply systems shall include the following:
- Disconnect switch(es).
- Motor starting device(s).
- Motor overload protection device(s).
- One or more compressors.
- For single, duplex, or multiple compressor systems, means for activation/deactivation of each individual compressor.
- When multiple compressors are used, manual or automatic means to alternate individual compressors.
- When multiple compressors are used, manual or automatic means to activate the additional unit(s) should the in-service unit(s) be incapable of maintaining adequate pressure.
- Intake filter-muffler(s) of the dry type.
- Receiver(s) with a manual or automatic drain.
- Shutoff valves.
- Compressor discharge check valve(s) (for multiple compressors).
- Air dryers that maintains a minimum of 40 percent relative humidity at operating pressure and temperature.
- In-line final particulate/coalescing filters rated at 0.01 micron (0.01 µm), with filter status indicator to ensure the delivery of dental air with a maximum allowable 0.05 ppm liquid oil.
- Pressure regulator(s).
- Pressure relief valve.
- Pressure indicator.
- Moisture indicator. [NFPA 99:126.96.36.199.1.1]
The medical air compressors shall draw their air from a source of clean air. [NFPA 99:188.8.131.52.3.11(A)]
If an air source equal to or better than outside air (e.g., air already filtered for use in operating room ventilating systems) is available, it shall be permitted to be used for the medical air compressors with the following provisions:
- This alternate source of supply air shall be available on a continuous 24 hours-per-day, 7 days-per-week basis.
- Ventilating systems having fans with motors or drive belts located in the airstream shall not be used as a source of medical air intake. [NFPA 99:184.108.40.206.3.11(E)]
Dental air sources for a compressor(s) shall meet the following requirements:
- If the intake is located inside the building, it shall be located within a space where no chemical-based materials are stored or used.
- If the intake is located inside the building, it shall be located in a space that is not used for patient medical treatment.
- If the intake is located inside the building, it shall not be taken from a room or space in which there is an open or semi-open discharge from a Category 3 vacuum system.
- If the intake is located outside the building, it shall be drawn from locations where no contamination from vacuum exhaust discharges or particulate matter is anticipated. [NFPA 99:220.127.116.11.1.5]
Medical air intakes shall be located as follows:
- The medical air intake shall be located a minimum of 25 feet (7620 mm) from ventilating system exhausts, fuel storage vents, combustion vents, plumbing vents, and vacuum discharges, or areas that can collect vehicular exhausts or other noxious fumes.
- The medical air intake shall be located a minimum of 20 feet (6096 mm) above ground level.
- The medical air intake shall be located a minimum of 10 feet (3048 mm) from any door, window, or other opening in the building. [NFPA 99:18.104.22.168.3.11(B-D)]
Air intakes for separate compressors shall be permitted to be joined together to one common intake where the following conditions are met:
- The common intake is sized to minimize backpressure in accordance with the manufacturer's recommendations.
- Each compressor can be isolated by manual or check valve, blind flange, or tube cap to prevent open inlet piping when the compressor(s) is removed for service from the consequent backflow of room air into the other compressor(s). [NFPA 99:22.214.171.124.3.11(G)]
The end of the intake shall be turned down and screened or otherwise be protected against the entry of vermin, debris, or precipitation by screening fabricated or composed of a noncorroding material. [NFPA 99:126.96.36.199.3.11(H)]
Receivers for medical air shall meet the following requirements:
- They shall be made of corrosion-resistant materials or otherwise be made corrosion resistant.
- They shall comply with Section VIII, "Unfired Pressure Vessels" of the ASME Boiler and Pressure Vessel Code.
- They shall be equipped with a pressure relief valve, automatic drain, manual drain, sight glass, and pressure indicator.
- They shall be of a capacity sufficient to prevent the compressor from short-cycling. [NFPA 99:188.8.131.52.3.6]
Receivers shall have the following:
- The capacity to prevent short-cycling of the compressor(s)
- Compliance with Section VIII, "Unfired Pressure Vessels" of the ASME Boiler and Pressure Vessel Code [NFPA 99:184.108.40.206.1.2]
A medical air receiver(s) shall be provided with proper valves to allow the flow of compressed air to enter and exit out of separate receiver ports during normal operation and allow the receiver to be bypassed during service without shutting down the supply of medical air. [NFPA 99:220.127.116.11.3.9(D)]