Where noncompliance with a provision of this Part (rule) causes or tends to cause imminent danger to a person employed in construction, demolition or excavation work and written notice thereof is given by the commissioner to the appropriate employer, owner, contractor or his agent, such person shall either (a) at once effect compliance sufficiently to end the danger, or (b) unless the commissioner does such posting or tagging on his behalf, forthwith post the dangerous area or tag the dangerous device or material with suitable posters or signs warning of the danger and forbidding unauthorized entry into the area or unauthorized use of the device or material, and shall maintain such posters or signs until the danger has been ended. While such noncompliance exists no employer shall suffer or permit any person employed by him to enter or be within an area or to use a device or material as to which he has received such a notice of imminent danger, or which is so posted or tagged, except to effect compliance with this Part (rule). No unauthorized person shall remove such poster or sign.