NOTE: In any case where there is a mixture in air of more than one radionuclide, the limiting values for purposes of the above table should be determined as follows:

1. If the identity and concentration of each radionuclide in the mixture are known, the limiting values should be derived as follows: Determine, for each radionuclide in the mixture, the ratio between the quantity present in the mixture and the limit otherwise established in the above table for the specific radionuclide when not in a mixture. The sum of such ratios for all the radio

If either the identity or the concentration of any radionuclide in the mixture is not known, the limiting values for purposes of this table shall be:

a. For purposes of Table I, Col. 1-1 X 10-12 b. For purposes of Table I, Col. 2-3 X 10-7

$ If the conditions specified below are met, the corresponding values specified below may be used in lieu of that specified in paragraph 2 above.

a. If the identity of each radionuclide in the mixture is known but the concentration of one or more of the radionuclides in the

mixture is not known, the concentration limit for the mixture is the limit specified in the table above for the radionuclide in the mixture having the lowest concentration limit; or

b. If the identity of each radionuclide in the mixture is not known, but it is known that certain radionuclides specified in the table above are not present in the mixture, the concentration limit for the mixture is the lowest concentration limit specified in the table above for any radionuclide which is not known to be absent from the mixture; or

4. If the mixture or radionuclides consists of uranium and its daughter products in ore dust prior to chemical processing of the uranium ore, the values specified below may be used in lieu of those determined in accordance with paragraph 1 above or those specified in paragraphs and 3 above.

1 X 10-10 μc/ml gross alpha activity; or 2.5 X 10-11 μc/ml natural uranium; or 75 micrograms natural uranium per cubic meter of air.

5. For purposes of this note, a radionuclide may be considered as not present in a mixture if (a) the ratio of the concentration of that radionuclide in the mixture (CA) to the concentration limit for that radionuclide specified in the above table (MPCA) does not exceed 10. (i.e.

§ 50-204.308 Precautionary procedures and personnel monitoring.

(a) Every employer shall make such surveys as may be necessary for him to comply with the regulations in this part. "Survey" means an evaluation of the radiation hazards incident to the production, use, release, disposal, or presence of radioactive materials or other sources of radiation under a specific set of conditions. When appropriate, such evaluation includes a physical survey of the location of materials and equipment, and measurements of levels of radiation or concentrations of radioactive material present.

(b) Every employer shall supply appropriate personnel monitoring equipment, such as film badges, pocket chambers, pocket dosimeters, or film rings, to, and require the use of such equipment by:

(1) Each employee who enters an area under such circumstances that he receives, or is likely to receive, a dose in any calendar quarter in excess of 25 percent of the applicable value specified in para

graph (a) of § 50-204.306; and

(2) Each employee under 18 years of age who enters an area under such circumstances that he receives, or is likely to receive, a dose in any calendar quarter in excess of 5 percent of the applicable value specified in paragraph (a) of § 50-204.306.

(3) Each employee who enters a high radiation area.

(c) As used in this part:

(1) "Personnel monitoring equipment" means devices designed to be worn or carried by an individual for the purpose of measuring the dose received (e.g., film badges, pocket chambers, pocket dosimeters, film rings, etc.);

(2) "Radiation area" means any area, accessible to personnel, in which there exists radiation, at such levels that a major portion of the body could receive in any one hour a dose in excess of 5 millirem, or in any 5 consecutive days a dose in excess of 100 millirems;

(3) "High radiation area" means any area, accessible to personnel, in which there exists radiation at such levels that a major portion of the body could receive in any one hour a dose in excess of 100 millirems.

[29 F.R. 1442, Jan. 29, 1964]

§ 50-204.309 signals.

Caution signs, labels, and

(a) General. (1) Symbols prescribed by this section shall use the conventional radiation caution colors (magenta or purple on yellow background). The symbol prescribed by this section is the conventional three-bladed design:

RADIATION SYMBOL

1. Cross-hatched area is to be magenta or purple.

2. Background is to be yellow.

(2) In addition to the contents of signs and labels prescribed in this section, employers may provide on or near such signs and labels any additional information which may be appropriate in aiding individuals to minimize exposure to radiation or to radioactive material.

60°

(b) Radiation areas. Each radiation area shall be conspicuously posted with a sign or signs bearing the radiation caution symbol and the words:

CAUTION"

RADIATION AREA

(c) High radiation areas. (1) Each high radiation area shall be conspicuously posted with a sign or signs bearing the radiation caution symbol and the words:

CAUTION 2

HIGH RADIATION AREA

(2) Each high radiation area shall be equipped with a control device which shall either cause the level of radiation to be reduced below that at which an individual might receive a dose of 100 millirem in one hour upon entry into the area or shall energize a conspicuous vis

" Or "Danger"

ible or audible alarm signal in such a manner that the individual entering and the employer or a supervisor of the activity are made aware of the entry. In the case of a high radiation area established for a period of 30 days or less, such control device is not required.

(d) Airborne radioactivity areas. (1) As used in the regulations in this part, "airborne radioactivity area" means (i) any room, enclosure, or operating area in which airborne radioactive materials, composed wholly or partly of radioactive material, exist in concentrations in excess of the amounts specified in Column 1 of § 50-204.307; or any room, enclosure, or operating area in which airborne radioactive material exists in concentrations which, averaged over the number of hours in any week during which individuals are in the area, exceed 25 percent of the amounts specified in Column 1 of § 50-204.307.

(2) Each airborne radioactivity area shall be conspicuously posted with a sign or signs bearing the radiation caution symbol and the words:

RADIOACTIVE MATERIAL (S)

(2) Each area or room in which natural uranium or thorium is used or stored in an amount exceeding one hundred times the quantity specified in paragraph (g) of this section shall be conspicuously posted with a sign or signs bearing the radiation caution symbol and the words: CAUTION 2

RADIOACTIVE MATERIAL (S)

(f) Containers. (1) Each container in which is transported, stored, or used a quantity of any radioactive material (other than natural uranium or thorium) greater than the quantity of such material specified in paragraph (g) of this section shall bear a durable, clearly visible label bearing the radiation caution symbol and the words:

CAUTION 2

RADIOACTIVE MATERIAL

(2) Each container in which natural uranium or thorium is transported, stored or used in a quantity greater than ten times the quantity specified in paragraph (g) of this section shall bear a durable, clearly visible label bearing the radiation caution symbol and the words:

CAUTION 2

RADIOACTIVE MATERIAL

(3) Notwithstanding the provisions of subparagraphs (1) and (2) of this paragraph a label shall not be required:

(i) If the concentration of the material in the container does not exceed that specified in § 50-204.307, Column 2 of this part, or

(ii) For laboratory containers, such as beakers, flasks, and test tubes, used transiently in laboratory procedures, when the user is present.

(4) Where containers are used for storage, the labels required in this paragraph shall state also the quantities and kinds of radioactive materials in the containers and the date of measurement of the quantities.

(g) Material.