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manner that, under conditions of normal use, the barrier always intercepts the entire useful beam; and

(4) collimators and adjustable diaphragms or shutters used to restrict the size of the useful beam must provide the same degree of protection as is required of the tube housing. (e) The exposure switch must be a dead-man type switch. (f) A manual-reset, cumulative timing device activated by the exposure switch must be used to either indicate elapsed exposure time by an audible signal or terminate the exposure when the total exposure exceeds a predetermined limit not exceeding five minutes in one or a series of exposures. (g) An audible alarm must sound continuously when operating the fluoroscope in high level control (HLC) mode. The limit for HLC is 20 roentgens per minute or 5.16 x 103 coulombs per kilogram per minute. (h) A shielding device of at least 0.25 millimeters lead equivalent material must be provided for covering the Bucky-slot during fluoroscopy. (i) Protective drapes, hinges, or sliding panels, of at least 0.25 millimeters lead equivalent material, must be provided between the patient and fluoroscopist to intercept scattered radiation which would otherwise reach the fluoroscopist and other individuals near the machine. These devices may not substitute for the wearing of a protective apron. (j) For routine fluoroscopy, the exposure rate measured at the point where the center of the useful beam enters the patient may not exceed 2.58 x 103 coulombs per kilogram per minute or 10 roentgens per minute, except during film recording of fluoroscopic images or when an optional high level control (HLC) is activated. (k) Mobile fluoroscopic equipment must meet the requirements of this section, where applicable, and the following requirements:

(1) in the absence of a table top, a cone or spacer frame must limit the target-to-skin distance to not less than 30 centimeters, except that for mini C-arms and for C-arms used during a surgical application to an extremity, the distance may not be less than 20 centimeters;

(2) image intensification must always be used;

(3) a machine must be inoperable, except when the collimating cone or diaphragm is in place and the entire useful beam is intercepted by the image intensifier; and

(4) the exposure rate measured 30 centimeters from the image intensifier or input phosphor must be as low as practical, but not exceed 10 roentgens per minute. (l) Each person, other than the patient, whose body is likely to be exposed to five milliroentgens per hour or more must wear a protective apron and gloves of at least 0.25 millimeters lead equivalent material in the fluoroscopy room.