The first (1st) public review of draft standard IIAR 4-201x, Installation of Closed-Circuit Ammonia Mechanical Refrigerating Systems is now open. Substantive changes resulting from this public review will also be provided for comment in a future public review if necessary. IIAR 4 specifies criteria for the installation of closed-circuit ammonia refrigeration systems. It presupposes that the persons who use the document have a working knowledge of the functionality of ammonia refrigerating system(s) and basic ammonia refrigerating practices and principles. This standard is intended for those who are involved with the installation of closed-circuit ammonia mechanical refrigeration systems. This standard shall apply only to closed-circuit mechanical refrigerating systems utilizing ammonia as the refrigerant. It supplements existing general refrigeration standards issued by IIAR and other organizations such as ASHRAE, ASME, and ANSI. It is not intended to supplant existing safety codes (e.g., model mechanical or fire codes or ASHRAE Standard 15).