N.H. Rev. Stat. § 270:33
No person shall put, place, operate, or cause to be put, placed, or operated in the waters of this state any so-called heating, agitating, or other device which inhibits or prevents the natural freezing of water, or forming of ice, and thereby impedes either the ingress or egress to or from the ice from any property other than that of the owner of the device. The person or persons responsible for the placement of the device shall ensure that warning signs are posted to warn of its location. Said signs shall read DANGER, THIN ICE and shall be of sufficient size to be readable at a distance of not less than 150 feet, and shall be visible from all directions and shall be equipped with reflectors and color-coded in a pattern unique for this purpose only. The department of safety is hereby authorized to establish said unique design and coloring and any homemade copies shall follow this design and coloring. The provisions of this section shall be enforced by any law enforcement agency under the direction of the department of safety pursuant to RSA 106-A:14 and the department of fish and game pursuant to RSA 206:26.
RSA 270:33
1973, 321:1, eff. Nov. 1, 1973. 2019, 37 : 1 , eff. July 14, 2019.