57.22229—Weekly testing (I-A, III, and V-A mines).
(a)
The mine atmosphere shall be tested for methane and carbon monoxide at least once every seven days by a competent person or an atmospheric monitoring system, or a combination of the two. Such testing shall be done at the following locations:
(b)
The volume of air (velocity in Subcategory I-A mines) shall be measured at least once every seven days by a competent person. Such measurement shall be done at the following locations:
(5)
In the last open crosscuts or other ventilation openings nearest the active faces where the air enters the return.
(c)
Where such examinations disclose hazardous conditions, affected persons shall be informed and corrective action shall be taken.
(d)
Certification of examinations shall be made by signature and date. Certifications shall be retained for at least one year and made available to authorized representatives of the Secretary.