Despite its complexities, there are some clear lines which can be drawn regarding the multiemployer doctrine. The first line to be drawn is between cases involving a hazardous physical condition and cases involving a hazard consisting of conduct by hourly employees of an outside contractor. Historically, OSHA had only applied the multiemployer doctrine to cases involving a physical condition, such as an improperly guarded machine, a hazardous confined space, an ungrounded electrical cord, or an unguarded platform. Further, where the hazard is a physical condition on the premises, it is likely that the host employer's own employees either created or would be exposed to the hazard. Typically, the host employer has the authority and ability to correct a hazardous physical condition.
Cases involving unsafe conduct by an outside contractor's employees present very different concerns.
This was the question in the IBP case. In IBP , the host employer operated a meat packing plant. Each night after production ceased for the day, an outside contractor came into the plant to sanitize the plant and all of the equipment within it. The contractor's hourly employees failed to lock out equipment and exposed only themselves to injury. The contractor had its own supervisors on the premises.