(c) Requirements-(1) Power density limit. The power density of the microwave radiation emitted by a microwave oven shall not exceed one (1) milliwatt per square centimeter at any point 5 centimeters or more from the external surface of the oven, measured prior to acquisition by a purchaser, and thereafter, 5 milliwatts per square centimeter at any point 5 centimeters or more from the external surface of the oven.

(2) Measurements and test conditions. (i) Compliance with the power density limit in this paragraph shall be determined by measurements of microwave power density made with an instrument system which (a) reaches 90 percent of its steady-state reading within 3 seconds when the system is subjected to a stepped input signal and which (b) has a radiation detector with an effective aperture of 25 square centimeters or less as measured in a plane wave, said aperture having no dimension exceeding 10 centimeters. This aperture shall be determined at the fundamental frequency of the oven being tested for compliance. The instrument system shall be capable of measuring the power density limits of this section with an accuracy of plus 25 percent and minus 20 percent (plus or minus 1 decibel).

(ii) Microwave ovens shall be in compliance with the power density limit if the maximum reading obtained at the location of greatest microwave leakage does not exceed the limit specified in subparagraph (1) of this paragraph when the leakage is measured through at least one stirrer cycle. Pursuant to § 78.203, manufacturers may request alternative test procedures if, as a result of the stirrer characteristics of a microwave oven, such oven is not susceptible to testing by the procedures described in this subdivision.

(iii) Measurements shall be made with the microwave oven operating at its maximum output and containing a load of 275±15 milliliters of tap water initially at 20° 5° centigrade placed within the cavity at the center of the load-carrying surface provided by the manufacturer. The water container shall be a low form 600 milliliter beaker having an inside diameter of approximately 8.5 centimeters and made of an electrically nonconductive material such as glass or plastic.

(iv) Measurements shall be made with the door fully closed as well as with the

door fixed in any other position which allows the oven to operate.

(3) Door and safety interlocks. (1) Microwave ovens shall have a minimum of two operative safety interiocks one of which must be concealed. A concealed safety interlock on a fully assembled microwave oven must not be operable by (a) any part of the body, or (b) a rod 3 millimeters or greater in diameter and with a useful length of 10 centimeters. A magnetically operated interlock is considered to be concealed only if a test magnet, held in place on the oven by gravity or its own attraction, cannot operate the safety interlock. The test magnet shall have a pull at zero air gap of at least 4.5 kilograms and a pull at 1 centimeter air gap of at least 450 grams when the face of the magnet which is toward the interlock switch when the magnet is in the test position is pulling against one of the large faces of a mild steel armature having dimensions of 80 millimeters by 50 millimeters by 8 millimeters.

(ii) Failure of any single mechanical or electrical component of the microwave oven shall not cause all safety interlocks to be inoperative.

(iii) Service adjustments or service procedures on the microwave oven shall not cause the safety interlocks to become inoperative or the microwave radiation leakage to exceed the power density limits of this section as a result of such service adjustments or procedures.

(iv) Insertion of an object into the oven cavity through any opening while the door is closed shall not cause microwave radiation leakage from the oven to exceed the applicable power density limits specified in this section.

(4) Instructions. Manufacturers of microwave ovens to which this section is applicable shall provide or cause to be provided:

(i) To servicing dealers and distributors and to others upon request, for each oven model, adequate instructions for service adjustments and service procedures including clear warnings of precautions to be taken to avoid possible exposure to microwave radiation;

(ii) With each oven, adequate instructions for its safe use including clear warnings of precautions to be taken to avoid possible exposure to microwave radiation.

[35 F.R. 15642, Oct. 6, 1970, as amended at 36 F.R. 23523, Dec. 10, 1971]

(a) Applicability. The provisions of § 78.213 are applicable as specified herein to:

(1) The following components of diagnostic x-ray systems which are manufactured after August 15, 1973: Tube housing assemblies, x-ray controls, x-ray high-voltage generators, fluoroscopic imaging assemblies, tables, cradles, film changers, cassette holders, and beam-limiting devices; and

(2) Diagnostic x-ray systems incorporating one or more of such components; however, such x-ray systems shall be required to comply only with those provisions of § 78.213 which relate to the components certified in accordance with paragraph (c) of this section and installed into the systems.

(b) Definitions. As used in § 78.213, the following definitions apply:

(1) "Accessible surface" means the external surface of the enclosure or housing provided by the manufacturer.

(2) "Aluminum equivalent" means the thickness of aluminum (type 1100 alloy) 1 affording the same attenuation, under specified conditions, as the material in question.

(3) "Assembler" means any person engaged in the business of assembling, replacing, or installing one or more components into an X-ray system subsystem.

or

(4) "Attenuation block" means a block or stack, having dimensions 20 centimeters by 20 centimeters by 3.8 centimeters, of type 1100 aluminum alloy or aluminum alloy having equivalent attenuation.

(5) "Automatic exposure control" means a device which automatically controls one or more technique factors in order to obtain at a preselected location (s) a required quantity of radiation.

(6) "Beam axis" means a line from the source through the centers of the X-ray fields.

1 The nominal chemical composition of type 1100 aluminum alloy is 99.00 percent minimum aluminum, 0.12 percent copper. "Aluminum Standards and Data," The Aluminum Association, New York, N.Y. (1969).

Estimated standard deviation of the population.

XMean value of observations in sample. n = Number of observations in sample. Number of observations in sample.

n

(9) "Control panel" means that part of the x-ray control upon which are mounted the switches, knobs, pushbuttons, and other hardware necessary for manually setting the technique factors.

(10) "Cooling curve" means the graphical relationship between heat units stored and cooling time.

(11) "Diagnostic source assembly" means the tube housing assembly with a beam-limiting device attached.

(12) "Diagnostic x-ray system" means an x-ray system designed for irradiation of any part of the human body for the purpose of diagnosis or visualization. (13) "Equipment" means x-ray equipment.

(14) "Exposure" means the quotient of dQ by dm where dQ is the absolute value of the total charge of the ions of one sign produced in air when all the electrons (negatrons and positrons) liberated by photons in a volume element of air having mass dm are completely stopped in air.

(15) "Field emission equipment" means equipment which uses an x-ray tube in which electron emission from the cathode is due solely to the action of an electric field.

(16) "Fluoroscopic imaging assembly" means a component which comprises a reception system in which x-ray photons produce a fluoroscopic image. It includes equipment housings, electrical interlocks if any, the primary protective barrier, and structural material providing linkage between the image receptor and the diagnostic source assembly.

(17) "General purpose radiographic x-ray system" means any radiographic X-ray system which, by design, is not limited to radiographic examination of specific anatomical regions.

(18) "Half-value layer, HVL" means the thickness of specified material which attenuates the beam of radiation to an extent such that the exposure rate is reduced to one-half of its original value. In this definition the contribution of all scattered radiation, other than any which might be present initially in the beam concerned, is deemed to be excluded.

(19) "Image receptor" means any device, such as a fluorescent screen or radiographic film, which transforms incident x-ray photons either into a visible image or into another form which can be made into a visible image by further transformations.

(20) "Leakage radiation" means radiation emanating from the diagnostic source assembly except for:

(i) The useful beam and

(ii) Radiation produced when the exposure switch or timer is not activated.

(21) "Leakage" technique factors means the technique factors associated with the tube housing assembly which are used in measuring leakage radiation. They are defined as follows:

(i) For capacitor energy storage equipment, the maximum rated number of exposures in an hour for operation at the maximum rated peak tube potential with the quantity of charge per exposure being 10 millicoulombs (mAs) or the minimum obtainable from the unit, whichever is larger.

(ii) For field emission equipment ratea for pulsed operation, the maximum rated number of x-ray pulses in an hour for operation at the maximum rated peak tube potential.

(iii) For all other equipment, the maximum rated continuous tube current for the maximum rated peak tube potential.

(22) "Light field" means that area of the intersection of the light beam from the beam-limiting device and one of the set of planes parallel to and including the plane of the image receptor, whose perimeter is the locus of points at which the illumination is one-fourth of the maximum in the intersection.

(23) "Line-voltage regulation" means the difference between the no-load and the load line potentials expressed as a percent of the load line potential; that

is,

Percent line-voltage regulation

=100 (Vn-V1) /Vi

(24) "Maximum line current" means the rms current in the supply line of an x-ray machine operating at its maximum rating.

(25) "Peak tube potential" means the maximum value of the potential difference across the x-ray tube during an exposure.

(26) "Primary protective barrier" means the material, excluding filters, placed in the useful beam to reduce the radiation exposure for protection purposes.

(27) "Rated line voltage" means the range of potentials, in volts, of the supply line specified by the manufacturer at which the x-ray machine is designed to operate.

(28) "Rated output current" means the maximum allowable load current of the x-ray high-voltage generator.

(29) "Rated output voltage" means the allowable peak potential, in volts, at the output terminals of the x-ray highvoltage generator.

(30) "Rating" means the operating limits specified by the manufacturer.

(31) "Recording" means producing a permanent form of an image resulting from x-ray photons (e.g., film, video tape).

(32) "Response time" means the time required for an instrument system to reach 90 percent of its final reading when the radiation-sensitive volume of the instrument system is exposed to a step change in radiation flux from zero sufficient to provide a steady state midscale reading.

(33) "Source" means the focal spot of the x-ray tube.

(34) "Source-image receptor distance, (SID)" means the distance from the source to the center of the input surface of the image receptor.

(35) "Stationary equipment” means equipment which is installed in a fixed location.

(36) "Technique factors" means the conditions of operation. They are specified as follows:

(i) For capacitor energy storage equipment, peak tube potential in kV and quantity of charge in mAs.

(ii) For field emission

equipment

rated for pulsed operation, peak tube potential in kV and number of x-ray pulses.

(iii) For all other equipment, peak tube potential in kV and either tube current in mA and exposure time in seconds,

or the product of tube current and exposure time in mAs.

(37) "Tubes" means an x-ray tube, unless otherwise specified.

(38) "Tube housing assembly" means the tube housing with tube installed. It includes high-voltage and/or filament transformers and other appropriate elements when they are contained within the tube housing.

(39) "Tube rating chart" means the set of curves which specify the rated limits of operation of the tube in terms of the technique factors.

(40) "Useful beam" means the radiation which passes through the tube housing port and the aperture of the beamlimiting device when the exposure switch or timer is activated.

(41) "Variable-aperture beam-limiting device" means a beam-limiting device which has capacity for stepless adjustment of the x-ray field size at a given SID.

(42) "Visible area" means that portion of the input surface of the image receptor over which incident x-ray photons produce a visible image.

(43) "X-ray control" means a device which controls input power to the x-ray high-voltage generator and/or the x-ray tube. It includes equipment which controls the technique factors of an x-ray exposure.

(44) "X-ray equipment" means an X-ray system, subsystem, or component thereof.

(45) "X-ray field" means that area of the intersection of the useful beam and any one of the set of planes parallel to and including the plane of the image receptor, whose perimeter is the locus of points at which the exposure rate is onefourth of the maximum in the intersection.

(46) "X-ray high-voltage generator" means a device which transforms electrical energy from the potential supplied by the x-ray control to the tube operating potential. The device may also include means for transforming alternating current to direct current, filament transformers for the x-ray tube(s), highvoltage switches, electrical protective devices, and other appropriate elements.

(47) "X-ray system" means an assemblage of components for the controlled production of x rays. It includes minimally an x-ray high-voltage generator, an x-ray control, a tube housing assembly, a beam-limiting device, and the necessary supporting structures. Ad

ditional components which function with the system are considered integral parts of the system.

(48) "X-ray subsystem" means any combination of two or more components of an x-ray system for which there are requirements specified in § 78.213.

(49) "X-ray tube" means any electron tube which is designed for the conversion of electrical energy into x-ray energy.

(c) Certification of components. Each component subject to § 78.213 shall be certified by the manufacturer thereof as a product which meets all applicable standards in accordance with the provisions of § 78.201. Certification that the product conforms to all applicable standards under this subpart shall be construed to mean that the component can meet the applicable provisions of § 78.213 if installed in a diagnostic x-ray system in accordance with instructions.

(d) Certification by assembler. An assembler who installs one or more components certified as required by paragraph (c) of this section into an x-ray system shall install certified components that are of the type required by § 78.213-2 or § 78.213-3 and, except as provided for in subparagraph (2) of this paragraph, shall assemble, install, adjust, and test the certified components in accordance with the instructions of their respective manufacturers. All assemblers who install certified components shall file a report of such assembly as specified in subparagraphs (1) and (2) of this paragraph. The report shall be construed as the assembler's certification and identification under §§ 78.201 and 78.202. All assembler reports shall be on a form prescribed by and available from the Director, Bureau of Radiological Health, 12720 Twinbrook Parkway, Rockville, Md. 20852. Completed reports shall be submitted to the Director, the purchaser, and, where applicable, to the State agency responsible for radiation protection, within 15 days following completion of the assembly.

(1) Reporting compliance. An assembler who installs one or more certified components into an x-ray system or subsystem, having properly followed the assembly instructions provided him by the component manufacturer, shall certify to this by filing a report containing the information prescribed on the form which shall include the following:

(i) The full name and address of the assembler and the date of assembly or installation.

(ii) The name and address of the purchaser and the location and specific identification of the X-ray system or subsystem.

(iii) An affirmation that all instruction manuals and other information as required by paragraph (h) of this section applicable to the newly installed x-ray equipment have been delivered to the purchaser.

(iv) A statement of the type and intended use of the x-ray system or subsystem into which the certified components were assembled or installed, such "radiographic-stationary general

as

purpose."

(v) A list of all certified components which were assembled or installed by him into the x-ray system or subsystem in accordance with the instructions of the component manufacturers, identifying the components by type, manufacturer, model number. and serial number.

(vi) An affirmation that the certified components listed pursuant to subdivision (v) of this subparagraph were assembled according to the instructions provided by the manufacturer (s) of such components.

(vii) An affirmation that all certified components installed in the x-ray system or subsystem were of the type required by § 78.213-2 or § 78.213-3.

(viii) An affirmation that a copy of this report will be transmitted to the purchaser and, where applicable, to the State agency responsible for radiation protection, in accordance with the requirements of this paragraph.

(2) Reporting noncompatibility. An assembler who installs a certified component into an x-ray system shall file a report indicating noncompatibility if he is unable to follow the instructions of the manufacturer of such certified component, provided other component(s) of the system do not meet the manufacturer's specifications for compatibility as given by the certified component manufacturer pursuant to paragraph (g) of this section and provided there is no commercially available certified component of a similar type which is compatible with the x-ray system. In addition, the component(s) of the system not meeting the specification for compatibility must either be of a type listed in paragraph (a) (1) of this section which does not bear a certification label due to date of manufacture, or if it is a component not of the type listed in paragraph (a) (1) of this section, it must have been

purchased as new prior to August 15, 1973. No assembler shall perform any modification of a certified component which will adversely affect the performance of the certified component with respect to the requirements of § 78.213. The assembler shall file a report indicating noncompatibility containing information prescribed on the form which shall include the following:

(i) The full name and address of the assembler and the date of assembly or installation.

(ii) The name and address of the purchaser and the location and specific identification of the x-ray system or subsystem.

(iii) An affirmation that all instruction manuals and other information as required by paragraph (h) of this section applicable to the newly installed X-ray equipment have been delivered to the purchaser.

(iv) A statement of the type or intended use of the x-ray system or subsystem into which the certified components were assembled or installed, such "radiographic-stationary general

as

purpose."

(v) A list of all certified component(s) which were assembled or installed by him into the x-ray system or subsystem and which could not be assembled, installed, adjusted, and tested in accordance with the manufacturer's instructions due to reasons specified in this subparagraph (this paragraph (d) (2)), identifying the components by type, manufacturer, model number, and serial number.

(vi) An affirmation that the certified component(s) listed pursuant to subdivision (v) of this subparagraph could not be assembled, installed, adjusted, and tested in accordance with the installation instructions of their respective manufacturers due to reasons specified in this subparagraph (this paragraph (d) (2)), and that no certified component was modified so as to adversely affect its performance with respect to the requirements of § 78.213.

(vii) For each certified component listed pursuant to subdivision (v) of this subparagraph, a full and complete explanation of why the manufacturer's installation instructions could not be followed in performing the assembly, including a listing by type, manufacturer, and model number of the incompatible component(s) already in the system, and either evidence of its date of purchase as