OSHA's respirable crystalline silica standard for general industry - 29 CFR 1910.1053 - defines a regulated area as "an area, demarcated by the employer, where an employee's exposure to airborne concentrations of respirable crystalline silica exceeds, or can reasonably be expected to exceed, the PEL." Section (e) of the standard - Regulated Areas - requires:
"(1) Establishment. The employer shall establish a regulate area whenever an employee’s exposure to airborne concentrations of respirable crystalline silica is, or can reasonably be expected to be, in excess of the PEL.
(2) Demarcation. The employer shall demarcate regulated areas from the rest of the workplace in a manner that minimizes the number of employees exposed to respirable crystalline silica within the regulated area.
(ii) The employer shall post signs at all entrances to regulated areas that bear the legend specified in paragraph (j)(2) of this section (see below).
(3) Access. The employer shall limit access to regulate areas to:
(A) Persons authorized by the employer and required by work duties to be present in the regulated area;
(B) Any persons entering such an area as a designated representative of employees for the purpose of exercising the right to observe monitoring procedures under paragraph (d) of this section; and
(C) Any persons authorized by the Occupational Safety and Health Act or regulations issued under it to be in a regulated area.”
(4) Provision of respirators. The employer shall provide each employee and the employee’s designated representative entering a regulated area with an appropriate respirator in accordance with paragraph (g) of this section (see below) and shall require each employee and the employee’s designated representative to use the respirator while in a regulated area.”
29 CFR 1910.1053(g) "Respiratory protection" states:
"(1) General. Where respiratory protection is required by this section, the employer must provide each employee an appropriate respirator that complies with the requirements of this paragraph and 29 CFR 1910.134. Respiratory protection is required:
(i) Where exposures exceed the PEL during periods necessary to install or implement feasible engineering and work practice controls;
(ii) Where exposures exceed the PEL during tasks, such as certain maintenance and repair tasks, for which engineering and work practice controls are not feasible;
(iii) During tasks for which an employer has implemented all feasible engineering and work practice controls and such controls are not sufficient to reduce exposures to or below the PEL; and
(iv) During periods when the employee is in a regulated area.
(2) Respiratory protection program. Where respirator use is required by this section, the employer shall institute a respiratory protection program in accordance with 29 CFR 1910.134.”
29 CFR 1910.1053(j) "Communication of respirable crystalline silica hazards to employees" (2) "Signs" states:
"The employer shall post signs at all entrances to regulated areas that bear the following legend:
DANGER
RESPIRABLE CRYSTALLINE SILICA
MAY CAUSE CANCER
CAUSES DAMAGE TO LUNGS
WEAR RESPIRATORY PROTECTION IN
THIS AREA
AUTHORIZED PERSONNEL ONLY”