Using exposed rebar as an anchorage point for a lifeline requires careful consideration and is generally not recommended unless specific conditions are met. Here's a breakdown of the safety concerns and requirements:

1. Strength and Suitability: The primary concern is whether the rebar can withstand the forces generated during a fall. A lifeline must be fastened to a secure anchor point with adequate breaking strength [1]. Regulations often specify minimum breaking strengths for anchor points [1]. Eyebolts, for example, have rated strength along their axis, which is greatly reduced if force is applied at an angle [2].

2. Design and Certification: Horizontal lifelines, in particular, require careful design. They should be designed and certified as safe by a professional engineer or manufactured to an approved standard [1]. The strength of horizontal lifelines and anchorages should be increased to account for the angle of sag and elasticity [3].

3. Roll-Out Prevention: Avoid direct connection of a snap-hook to rebar unless properly designed locking snap-hooks are used [2]. Ensure proper dimensions of the rebar in relation to the snap-hook dimensions to prevent the snap-hook keeper from being depressed by a turning motion [2].

4. Alternatives: Consider alternative tie-off rigging, such as a snap-hook/dee-ring connection or an abrasion-resistance strap around the rebar [3].

5. Inspection and Maintenance: Anchor points must be inspected and certified by a competent person before first use, regularly (at least every 12 months), and after any event or maintenance [4]. If any defect or inadequacy is found, the anchor point must not be used until the issue is resolved [4].

6. Competent Person: A competent person should inspect the connecting linkage, personal fall arrest system, full-body harness, or lifeline as recommended by the manufacturer and after any fall-arresting incident to determine if it is safe for continued use [5].

7. Protruding Rebar: Be aware that all protruding reinforcing steel, onto and into which employees could fall, shall be guarded to eliminate the hazard of impalement [6].

In summary, using rebar as a lifeline anchor is not advisable without thorough evaluation by a qualified person to ensure it meets all safety and regulatory requirements. If the rebar is deemed unsuitable, explore alternative anchorage methods.