This Recommended Practice provides guidance for optical measurements associated with laser safety requirements. The information contained in this document is intended to assist users who are entrusted with the responsibility of conducting laser hazard evaluations to ensure that appropriate control measures are implemented. It contains clearly written definitions, examples, and other practical information for manufacturers, laser safety officers, technicians, and other trained laser users. This revision of the original 2005 standard harmonizes with the revised ANSI Z136.1 - 2007 Safe Use of Lasers standard, parent document and cornerstone of the ANSI Z136 laser safety standards series and the foundation of laser safety programs nationwide. Other changes include the addition of many new important terms and definitions as well as revised definitions from the 2005 standard. Significant revisions can also be seen in updated figures, tables and charts as well as revised and new sections throughout the standard.