N.M. Stat. § 50-10-1
It shall be unlawful for any person, firm or corporation to require, authorize or knowingly permit any person in the employ or subject to the control of such person, firm or corporation, to enter through a manhole or otherwise into any sewer in this state, whether the same is in service or under construction, without first testing the atmosphere in said sewer at the place or places of entry by use of apparatus to detect the presence of any flammable gas or vapor; and in the event the presence of any flammable gas or vapor is so detected, it shall be unlawful for any such person, firm or corporation to require, authorize or knowingly permit any such employee or controlled person to enter into said sewer unless and until the same has been, at the intended place or places of entry, adequately ventilated and made safe from the hazards of fire and explosion.
NMS § 50-10-1