[Code of Federal Regulations]
[Title 21, Volume 8]
[Revised as of April 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 21CFR1020.20]

[Page 601-602]
 
                        TITLE 21--FOOD AND DRUGS
 
CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN 
                          SERVICES (CONTINUED)
 
PART 1020--PERFORMANCE STANDARDS FOR IONIZING RADIATION EMITTING PRODUCTS--Table of Contents
 
Sec. 1020.20  Cold-cathode gas discharge tubes.

    (a) Applicability. The provisions of this section are applicable to 
cold-cathode gas discharge tubes designed to demonstrate the effects of 
a flow of electrons or the production of x-radiation as specified 
herein.
    (b) Definitions. Beam blocking device means a movable or removable 
portion of any enclosure around a cold-cathode gas discharge tube, which 
may be opened or closed to permit or prevent the emergence of an exit 
beam.
    Cold-cathode gas discharge tube means an electronic device in which 
electron flow is produced and sustained by ionization of contained gas 
atoms and ion bombardment of the cathode.
    Exit beam means that portion of the radiation which passes through 
the aperture resulting from the opening of the beam blocking device.
    Exposure means the sum of the electrical charges on all of the ions 
of one sign produced in air when all electrons liberated by photons in a 
volume element of air are completely stopped in air divided by the mass 
of the air in the volume element. The special unit of exposure is the 
roentgen. One (1) roentgen equals 2.58x10-4 coulombs/
kilogram.
    (c) Requirements--(1) Exposure rate limit. (i) Radiation exposure 
rates produced by cold-cathode gas discharge tubes shall not exceed 10 
mR./hr. at a distance of thirty (30) centimeters from any point on the 
external surface of the tube, as measured in accordance with this 
section.
    (ii) The divergence of the exit beam from tubes designed primarily 
to demonstrate the effects of x radiation, with the beam blocking device 
in the open position, shall not exceed (Pi) steradians.
    (2) Measurements. (i) Compliance with the exposure rate limit 
defined in paragraph (c)(1)(i) of this section shall be determined by 
measurements averaged over an area of one hundred (100) square 
centimeters with no linear dimension greater than twenty (20) 
centimeters.
    (ii) Measurements of exposure rates from tubes in enclosures from 
which the tubes cannot be removed without destroying the function of the 
tube may be made at a distance of thirty (30) centimeters from any point 
on the external surface of the enclosure, provided:
    (a) In the case of enclosures containing tubes designed primarily to 
demonstrate the production of x radiation, measurements shall be made 
with any beam blocking device in the beam blocking position, or
    (b) In the case of enclosures containing tubes designed primarily to 
demonstrate the effects of a flow of electrons, measurements shall be 
made with all movable or removable parts of such enclosure in the 
position which would maximize external exposure levels.

[[Page 602]]

    (3) Test conditions. (i) Measurements shall be made under the 
conditions of use specified in instructions provided by the 
manufacturer.
    (ii) Measurements shall be made with the tube operated under forward 
and reverse polarity.
    (4) Instructions, labels, and warnings. (i) Manufacturers shall 
provide, or cause to be provided, with each tube to which this section 
is applicable, appropriate safety instructions, together with 
instructions for the use of such tube, including the specification of a 
power source for use with the tube.
    (ii) Each enclosure or tube shall have inscribed on or permanently 
affixed to it, tags or labels, which identify the intended polarity of 
the terminals and:
    (a) In the case of tubes designed primarily to demonstrate the heat 
effect, fluorescence effect, or magnetic effect, a warning that 
application of power in excess of that specified may result in the 
production of x-rays in excess of allowable limits; and (b) in the case 
of tubes designed primarily to demonstrate the production of x-
radiation, a warning that this device produces x-rays when energized.
    (iii) The tag or label required by this paragraph shall be located 
on the tube or enclosure so as to be readily visible and legible when 
the product is fully assembled for use.