(a) Each operator shall take five valid representative samples every calendar quarter from the environment of each part 90 miner while performing normal work duties. Part 90 miner samples shall be collected on consecutive work days. The quarterly periods are:

(b) When the respirable dust standard is changed in accordance with §90.101, the new applicable standard shall become effective 7 calendar days after the date of notification of the change by MSHA.

(c) When a valid representative sample taken in accordance with this section meets or exceeds the excessive concentration value (ECV) in Table 90-1 that corresponds to the applicable standard and particular sampling device used, the operator shall:

(1) Make approved respiratory equipment available to affected miners in accordance with §72.700 of this chapter;

(2) Immediately take corrective action to lower the concentration of respirable coal mine dust to at or below the applicable standard; and

(3) Make a record of the corrective actions taken. The record shall be certified by the mine foreman or equivalent mine official, no later than the end of the mine foreman's or equivalent official's next regularly scheduled working shift. The record shall be made in a secure book that is not susceptible to alteration or electronically in a computer system so as to be secure and not susceptible to alteration. Such records shall be retained at a surface location at the mine for at least 1 year and shall be made available for inspection by authorized representatives of the Secretary and the part 90 miner.

(d) Noncompliance with the applicable standard is demonstrated during the sampling period when:

(1) Two or more valid representative samples meet or exceed the ECV in Table 90-1 that corresponds to the applicable standard and the particular sampling device used; or

(2) The average for all valid representative samples meets or exceeds the ECV in Table 90-2 that corresponds to the applicable standard and the particular sampling device used.

(e) Unless otherwise directed by the District Manager, upon issuance of a citation for a violation of the applicable standard, paragraph (a) of this section shall not apply to that part 90 miner until the violation is abated and the citation is terminated in accordance with paragraphs (f) and (g) of this section.

(f) Upon issuance of a citation for a violation of the applicable standard, the operator shall take the following actions sequentially:

(1) Make approved respiratory equipment available to the affected part 90 miner in accordance with §72.700 of this chapter.

(2) Immediately take corrective action to lower the concentration of respirable dust to at or below the applicable standard. If the corrective action involves:

(i) Reducing the respirable dust levels in the work position of the part 90 miner identified in the citation, the operator shall implement the proposed corrective actions and begin sampling the affected miner within 8 calendar days after the date the citation is issued, until five valid representative samples are taken.

(ii) Transferring the part 90 miner to another work position at the mine to meet the applicable standard, the operator shall comply with §90.102 of this part and then sample the affected miner in accordance with §90.206(a) of this part.

(3) Make a record of the corrective actions taken. The record shall be certified by the mine foreman or equivalent mine official, no later than the end of the mine foreman's or equivalent official's next regularly scheduled working shift. The record shall be made in a secure book that is not susceptible to alteration or electronically in a computer system so as to be secure and not susceptible to alteration. Such records shall be retained at a surface location at the mine for at least 1 year and shall be made available for inspection by authorized representatives of the Secretary and the part 90 miner.

(g) A citation for a violation of the applicable standard shall be terminated by MSHA when the equivalent concentration of each of the five valid representative samples is at or below the applicable standard.