33 C.F.R. § 127.201

(a) Fixed sensors must have audio and visual alarms in the control room and audio alarms nearby.

(b) Fixed sensors that continuously monitor for LNG vapors must—

(1) Be in each enclosed area where vapor or gas may accumulate; and

(2) Meet Section 16.4 of NFPA 59A (incorporated by reference, see § 127.003).

(c) Fixed sensors that continuously monitor for flame, heat, or products of combustion must—

(1) Be in each enclosed or covered Class I, Division 1, hazardous location defined in Section 500.5(B)(1) of NFPA 70 (incorporated by reference, see § 127.003) and each area in which flammable or combustible material is stored; and

(2) Meet Section 16.4 of NFPA 59A (incorporated by reference, see § 127.003).