Replaced R11 in low pressure centrifugal chillers. New R123 equipment has been engineered with the correct materials of construction and sized properly for the intended job. Retrofitting existing R11 chillers to R123 may require replacement of seals, gaskets, and other system components to obtain the correct operation conditions and prevent leaks. The ASHRAE safety rating for R123 is B1, which indicates that lower levels for personal exposure are allowed in normal daily operation and service conditions. Extra precautions and machinery room requirements must be observed (specific requirements are spelled out in ASHRAE Standard 15, Safety Code for Mechanical Refrigeration).