Know the Law One book is absolutely essential for what employers and workers need to know about health and safety on site. That's the Occupational Health and Safety Act and Regulations for Construction Projects. Regulations covering every aspect of construction health and safety are spelled out in the "green book." Employers are required to post a copy on site. The green book is available from Publications Ontario at 416-326-5300 or from CSAO at 416-674-2726 or 1-800-781-2726.